Lecture № 15

Di- and Di- and ppolysaccharidesolysaccharides..

TerpenesTerpenes..

Ass. Medvid I.I.Ass. Medvid I.I.Ass. Burmas N.IAss. Burmas N.I

OutlineOutline1.1. Oligosaccharides.Oligosaccharides.2.2. The following functions of carbohydrates in humans. The following functions of carbohydrates in humans. 3.Classification of disaccharides:3.Classification of disaccharides:a)a) maltose;maltose;b)b) cellobiose;cellobiose;c)c) lactose;lactose;d)d) saccharose.saccharose. 4. Polysaccharides (glucanes).4. Polysaccharides (glucanes).a) Homopolysaccharides:a) Homopolysaccharides:- Structure, composition and properties of- Structure, composition and properties of cellulose.cellulose.- Structure, composition and properties of- Structure, composition and properties of starch.starch.- Glycogen, dextranes, inuline, pectin compounds, chitin.- Glycogen, dextranes, inuline, pectin compounds, chitin.b) Heteropolysaccharides.b) Heteropolysaccharides.5. Glycoconjugates.5. Glycoconjugates.

6. Lipids.6. Lipids.7. Chemical properties of fats7. Chemical properties of fats8. Phospholipids. 8. Phospholipids. WaxesWaxes..9. 9. Nonsaponifiable lipids. Nonsaponifiable lipids. 10. Terpenes and terpenoids. 10. Terpenes and terpenoids. Terpene biosynthesis.Terpene biosynthesis.11. 11. Classification of Classification of tterpeneserpenes..12. 12. CarotenoidsCarotenoids.. 13. 13. SteroidsSteroids..14. Properties of cholesterol.14. Properties of cholesterol. Biosynthesis of Biosynthesis of ccholesterolholesterol..15. Vitamins.15. Vitamins.16. Water-soluble vitamins.16. Water-soluble vitamins.17.Water insoluble (lipid-soluble) vitamins.17.Water insoluble (lipid-soluble) vitamins.

1.1.Oligosaccharides.Oligosaccharides.• The term “The term “oligosaccharide”oligosaccharide” is often used for carbohydrates is often used for carbohydrates

that consist of between two and ten monosaccharide units.that consist of between two and ten monosaccharide units.Oligosaccharides are carbohydrates that contain from two to ten Oligosaccharides are carbohydrates that contain from two to ten monosaccharide units. monosaccharide units.

• Disaccharides Disaccharides are the most common type of oligosaccharide. are the most common type of oligosaccharide. Disaccharides are carbohydrates composed of two Disaccharides are carbohydrates composed of two monosaccharide units covalently bonded to each other. Like monosaccharide units covalently bonded to each other. Like monosaccharides, disaccharides are crystalline, water-soluble monosaccharides, disaccharides are crystalline, water-soluble substances. substances. SaccharoseSaccharose (table sugar) and (table sugar) and lactoselactose (milk sugar) (milk sugar) are disaccharides. Within the human body, oligosaccharides are are disaccharides. Within the human body, oligosaccharides are often found associated with proteins and lipids in complexes often found associated with proteins and lipids in complexes that have both structural and regulatory functions. Free that have both structural and regulatory functions. Free oligosaccharides, other than disaccharides, are seldom oligosaccharides, other than disaccharides, are seldom encountered in biological systemsencountered in biological systems

• Complete hydrolysis of an oligosaccharide produces Complete hydrolysis of an oligosaccharide produces monosaccharides. Upon hydrolysis, а disaccharide produces monosaccharides. Upon hydrolysis, а disaccharide produces two monosaccharides, а trisaccharide three monosaccharides, а two monosaccharides, а trisaccharide three monosaccharides, а hexasaccharide six monosaccharides, and so on.hexasaccharide six monosaccharides, and so on.

• Carbohydrates are the most abundant class of bioorganic Carbohydrates are the most abundant class of bioorganic molecules on planet Earth. Although their abundance in the molecules on planet Earth. Although their abundance in the human body is relatively low, carbohydrates constitute about human body is relatively low, carbohydrates constitute about 75% by mass of dry plant materials.75% by mass of dry plant materials.

• Green (chlorophyll-containing) plants produce carbohydrates Green (chlorophyll-containing) plants produce carbohydrates via photosynthesis. In this process, carbon dioxide from the air via photosynthesis. In this process, carbon dioxide from the air and water from the soil are the reactants, and sunlight and water from the soil are the reactants, and sunlight absorbed by chlorophyll is the energy source. absorbed by chlorophyll is the energy source.

• Plants have two main uses for the carbohydrates they produce. Plants have two main uses for the carbohydrates they produce. In the form of cellulose, carbohydrates serve as structural In the form of cellulose, carbohydrates serve as structural elements, and in the form of starch, they provide energy elements, and in the form of starch, they provide energy reserves for the plants.reserves for the plants.

• Dietary intake of plant materials is the major carbohydrate Dietary intake of plant materials is the major carbohydrate source for humans and animals. The average human diet source for humans and animals. The average human diet should ideally be about two-thirds carbohydrate by mass.should ideally be about two-thirds carbohydrate by mass.

2. The following functions of carbohydrates in 2. The following functions of carbohydrates in humans.humans.

Carbohydrates have the following functions in Carbohydrates have the following functions in humans:humans:

1. Carbohydrate oxidation provides energy1. Carbohydrate oxidation provides energy2. Carbohydrate storage, in the form of glycogen, 2. Carbohydrate storage, in the form of glycogen,

provides а short- term energy reserve.provides а short- term energy reserve. 3. Carbohydrates supply carbon atoms for the synthesis 3. Carbohydrates supply carbon atoms for the synthesis

of other biochemical substances (proteins, lipids, and of other biochemical substances (proteins, lipids, and nucleic acids).nucleic acids).

4. Carbohydrates form part of the structural framework 4. Carbohydrates form part of the structural framework of DNA and RNA molecules.of DNA and RNA molecules.

5. Carbohydrate "markers" on cell surfaces play key 5. Carbohydrate "markers" on cell surfaces play key roles in cell -cell recognition processes.roles in cell -cell recognition processes.

3.Classification of disaccharides3.Classification of disaccharides

(1) Nоn-reducing disaccharides(1) Nоn-reducing disaccharides. In these disaccharides the . In these disaccharides the two hexose units are linked together through their two hexose units are linked together through their reducing (i е. aldehydic or ketonic) groups which is , reducing (i е. aldehydic or ketonic) groups which is , in aldoses and , in ketoses. Now in such cases since in aldoses and , in ketoses. Now in such cases since the reducing groups of both hexoses are lost, the resulting the reducing groups of both hexoses are lost, the resulting compound (disaccharide) will be non-reducing. Hence compound (disaccharide) will be non-reducing. Hence such disaccharides do not form osazone do not show such disaccharides do not form osazone do not show mutarotation and do not react with reagents like Feling’s mutarotation and do not react with reagents like Feling’s solution, Tollen’s reagent, etc. Important example of non-solution, Tollen’s reagent, etc. Important example of non-reducing disaccharides is saccharose.reducing disaccharides is saccharose.

(2) Reducing disaccharides.(2) Reducing disaccharides. In these disaccharides, In these disaccharides, one hexose unit is linked through its reducing carbon to one hexose unit is linked through its reducing carbon to the non-reducing carbon (C4 or С6) of the other Now the non-reducing carbon (C4 or С6) of the other Now since the reducing group of one of the hexoses is not since the reducing group of one of the hexoses is not involved, the resulting disaccharide will be а reducing involved, the resulting disaccharide will be а reducing sugar. sugar. MaltoseMaltose and and lactoselactose are examples of reducing are examples of reducing disaccharides.disaccharides.

• As mentioned earlier, disaccharides are those sugars which on As mentioned earlier, disaccharides are those sugars which on hydrolysis give two moles of monosaccharides general these are hydrolysis give two moles of monosaccharides general these are sweet-testing crystalline, water-soluble substances, easily sweet-testing crystalline, water-soluble substances, easily hydrolysed by enzymes and dilute mineral acids. The common hydrolysed by enzymes and dilute mineral acids. The common disaccharides have the general formula disaccharides have the general formula CC1212HH2222OO1111 which during which during hydrolysis take one molecule of water to form two hexoses.hydrolysis take one molecule of water to form two hexoses.

• Disaccharides are formed by intermolecular dehydration Disaccharides are formed by intermolecular dehydration between two monosaccharide molecules, e.g. In the formation between two monosaccharide molecules, e.g. In the formation of disaccharides, at least one monosaccharide unit is linked to of disaccharides, at least one monosaccharide unit is linked to the other through the glycosidic carbon atom. In other words we the other through the glycosidic carbon atom. In other words we can say that in the formation of disaccharide, reducing property can say that in the formation of disaccharide, reducing property of at least one hexose unit is lost. Hence disaccharides may be of at least one hexose unit is lost. Hence disaccharides may be considered as glycosides in which both components of the considered as glycosides in which both components of the molecules are sugars. Disaccharides may exist in two types, molecules are sugars. Disaccharides may exist in two types, namely non-reducing and reducing depending on the fact that namely non-reducing and reducing depending on the fact that С1 of one hexose is linked to the carbonyl carbon at other С1 of one hexose is linked to the carbonyl carbon at other carbon atom of other hexose. Weak oxidizing agents, such as carbon atom of other hexose. Weak oxidizing agents, such as Tollens, Feling's, and Benedict's solutions, oxidize the carbonyl Tollens, Feling's, and Benedict's solutions, oxidize the carbonyl group end of group end of аа monosaccharide to give an - monosaccharide to give an -onic acidonic acid..

Disaccharides. Disaccharides. А monosaccharide that has cyclic forms А monosaccharide that has cyclic forms (hemiacetal or hemiketal) can react with an alcoho1 to form а (hemiacetal or hemiketal) can react with an alcoho1 to form а glycoside (acetal or ketal). This same type of reaction can be glycoside (acetal or ketal). This same type of reaction can be used to produce а disaccharide, а carbohydrate in which two used to produce а disaccharide, а carbohydrate in which two monosaccharides are bonded together. In disaccharide formation, monosaccharides are bonded together. In disaccharide formation, one of the monosaccharide reactants functions as а hemiacetal or one of the monosaccharide reactants functions as а hemiacetal or hemiketal, and the other functions as an alcohol.hemiketal, and the other functions as an alcohol.

Monosaccharide + monosaccharide = disaccharide + НMonosaccharide + monosaccharide = disaccharide + Н22OO

The bond that links the two monosaccharides of а disaccharide together is called а glycosidic The bond that links the two monosaccharides of а disaccharide together is called а glycosidic linkage. А glycosidic linkage is the carbon-oxygen-carbon bond that joins the two components of linkage. А glycosidic linkage is the carbon-oxygen-carbon bond that joins the two components of а glycoside together. The bond that links the two monosaccharides of а disaccharide together is а glycoside together. The bond that links the two monosaccharides of а disaccharide together is called а glycosidic linkage. We now examine the structures and properties of four important called а glycosidic linkage. We now examine the structures and properties of four important disaccharides: maltose, cellobiose, lactose, and saccharose. As we consider details of the structures disaccharides: maltose, cellobiose, lactose, and saccharose. As we consider details of the structures of these compounds, we will find that the configuration (of these compounds, we will find that the configuration (αα or or ββ) at carbon-1 of the reacting ) at carbon-1 of the reacting monosaccharides is often of prime importance. monosaccharides is often of prime importance.

MaltoseMaltose, often called malt sugar, is produced by , often called malt sugar, is produced by breaking down the polysaccharide starch, as takes place in breaking down the polysaccharide starch, as takes place in plants when seeds germinate and in human beings during plants when seeds germinate and in human beings during starch digestion. It is starch digestion. It is аа common ingredient in baby foods and is common ingredient in baby foods and is found in malted milk. Malt (germinated barley that has been found in malted milk. Malt (germinated barley that has been baked and ground) contains maltose; hence the name malt baked and ground) contains maltose; hence the name malt sugar. Structurally, maltose is made up of two D-sugar. Structurally, maltose is made up of two D-glucopyranose units, one of which must be glucopyranose units, one of which must be -D-glucose. The -D-glucose. The formation of maltose from two glucose molecules is as follows:formation of maltose from two glucose molecules is as follows:

-D-Glucose -D-Glucose -D-Glucose -D-Glucose -(1-4)-linkage -(1-4)-linkage

So, α-maltose can be named as 4-O-(α-D-glucopyranosido)-α-D-glucopyranose, β-maltose – 4-O-(α-D-glucopyranosido)-β-D-glucopyranose.

The glycosidic linkage between the two glucose units is called The glycosidic linkage between the two glucose units is called an an (1 - 4) linkage. The two ОН-groups that form the linkage (1 - 4) linkage. The two ОН-groups that form the linkage are attached, respectively, to carbon-1 of the first glucose unit are attached, respectively, to carbon-1 of the first glucose unit (in an a configuration) and to carbon-4 of the second. Maltose (in an a configuration) and to carbon-4 of the second. Maltose is а reducing sugar, because the glucose unit on the right has а is а reducing sugar, because the glucose unit on the right has а hemiacetal carbon atom (С-1).Thus this glucose unit can open hemiacetal carbon atom (С-1).Thus this glucose unit can open and close; it is in equilibrium with its open-chain aldehyde and close; it is in equilibrium with its open-chain aldehyde form. This means there are actually three forms of the maltose form. This means there are actually three forms of the maltose molecule: molecule: -maltose, -maltose, -maltose, and the open-chain form. In -maltose, and the open-chain form. In the solid state, the the solid state, the -form is dominant. The most important -form is dominant. The most important chemical reaction of maltose is hydrolysis. Hydrolysis of D-chemical reaction of maltose is hydrolysis. Hydrolysis of D-maltose, whether in а laboratory flask or in а living organism, maltose, whether in а laboratory flask or in а living organism, produces two molecules of D-glucose.produces two molecules of D-glucose.

O O O O H

O H

OH

H

H

H

H

HH

H

HO

OH

HO

CH2

OH CH2

OH

OHOH

OHOH

[ O ]H

H

H

H

H

HH

H

HOHO

CH2

OH CH2

OH

OHOH

OHOH C

maltoboinic acid

O O O OH

H

H

HHH

H

HOOH

HO

CH2OH CH 2OH

OHOH

OHOH

CH3OH (HCl, gas)H

H

H

HHH

H

HOOCH 3

HO

CH2OH CH

2OH

OHOH

OHOH

methylmaltozide

O O

O O

O O

HH

H

HHH

H

HOOH

HO

CH2OH CH2OH

OHOH

OHOH

CH3J або (CH3)2SO4

(CH3CO)2O

(Ac = CH3CO)

HH

H

HHH

HOOCH3

CH3O

CH2OCH3CH2OCH3

OCH3OCH3

OCH3

HH

H

HHH

HOOAc

AcO

CH2OAc CH2OAc

OAcOAc

OAcOAc

H

H

H

H

H

OCH3

HOH, H+

HOH, H+

O O

O O

HOH, H+

HH

H

HHH

OOH

CH3O

CH2OCH3CH2OCH3

OCH3OCH3

OCH3

H

HOCH3

+ CH3OH

HOH, H+ HH H

HH

HOOH

AcO

CH2OAc CH2OAc

OAcOAc

OAcOAc H+ CH3COOH

H H

CellobioseCellobiose is produced as an intermediate in the is produced as an intermediate in the hydrolysis of the polysaccharide cellulose. Like maltose, hydrolysis of the polysaccharide cellulose. Like maltose, cellobiose contains two cellobiose contains two D-glucoseD-glucose monosaccharide units. It monosaccharide units. It differs from maltose in one of D-glucose units - the one differs from maltose in one of D-glucose units - the one functioning as а hemiacetal - must have а functioning as а hemiacetal - must have а -configuration -configuration instead of the а configuration of maltose. This change in instead of the а configuration of maltose. This change in configuration gives а configuration gives а (1-4) glycosidic linkage.(1-4) glycosidic linkage.

-D-Glucose (1-4)-linkage

α-cellobiose can be named as 4-O-(β-D-glucopyranosido)-α-D-glucopyranose, β-cellobiose – 4-O-(β-D-glucopyranosido)-β-D-glucopyranose.

Like maltose, cellobiose is a reducing sugar, has three Like maltose, cellobiose is a reducing sugar, has three isomeric forms in aqueous solution, and upon hydrolysis isomeric forms in aqueous solution, and upon hydrolysis produces two produces two D-glucoseD-glucose molecules. Despite these similarities, molecules. Despite these similarities, maltose and cellobiose have different biological behaviors. maltose and cellobiose have different biological behaviors. These differences are related to the stereochemistry of their These differences are related to the stereochemistry of their glycosidic linkages. glycosidic linkages. MaltaseMaltase, the enzyme that breaks the , the enzyme that breaks the glucose-glucose glucose-glucose (1-4) linkage present in maltose, is found (1-4) linkage present in maltose, is found both in the human body and in yeast. Consequently, maltose is both in the human body and in yeast. Consequently, maltose is digested easily by humans and is readily fermented by yeast. digested easily by humans and is readily fermented by yeast. Both the human body and yeast lack the enzyme Both the human body and yeast lack the enzyme cellobiasecellobiase needed to break the glucose - glucose needed to break the glucose - glucose (1-4) linkage of (1-4) linkage of cellobiose. Thus cellobiose cannot be digested by humans or cellobiose. Thus cellobiose cannot be digested by humans or fermented by yeast. In maltose and cellobiose, the two units of fermented by yeast. In maltose and cellobiose, the two units of the disaccharide are identical - two glucose units in each case. the disaccharide are identical - two glucose units in each case. Maltose and cellobiose have different arrangement in space. In Maltose and cellobiose have different arrangement in space. In maltose molecule maltose molecule αα-glycosidic linkage has axial arrangement, -glycosidic linkage has axial arrangement, in cellobiose molecule in cellobiose molecule ββ-glycosidic linkage – equatorial. Its -glycosidic linkage – equatorial. Its cases club-similar structure of amylose and linear structure of cases club-similar structure of amylose and linear structure of cellulose.cellulose.

LactoseLactose includes includes -D-galactopyranose unit and а D--D-galactopyranose unit and а D-glucopyranose unit joined by glucopyranose unit joined by -(1-4) glycosidic linkage-(1-4) glycosidic linkage

-D-galactose -D-Glucose (1-4)-linkage The glucose hemiacetal center is active when galactose bonds to glucose in the formation of lactose, so lactose is а reducing sugar (the glucose ring can open to give an aldehyde).Lactose is the major sugar found in milk. This accounts for its common name, milk sugar. Enzymes in animal mammary glands take glucose from the bloodstream and synthesize lactose in а four-step process. Epimerization of glucose yields galactose, and then the (1-4) linkage forms between а galactose and а glucose unit. Lactose is an important ingredient in commercially produced infant formulas that are designed to simulate mother' s milk. Souring of milk is caused by the conversion of lactose to lactic acid by bacteria in the milk. Pasteurization of milk is а quick-heating process that kills most of the bacteria and retards the souring process. Lactose can be hydrolyzed by acid or by the enzyme lactase, forming an equimolar mixture of galactose and glucose. In the human body, the galactose produced in such way is then converted to glucose by other enzymes. The genetic condition lactose intolerance, an inability of the human digestive system to hydrolyze lactose.

α-lactose can be named as 4-O-(β-D-galactopyranosido)-α-D-glucopyranose, β-lactose – 4-O-(β-D-galactopyranosido)-β-D-glucopyranose.

Arrangement in space is similar to cellobiose:

SaccharoseSaccharose, common table sugar, is the most , common table sugar, is the most abundant of all disaccharides and occurs throughout abundant of all disaccharides and occurs throughout the plant kingdom. It is produced commercially from the plant kingdom. It is produced commercially from the juice of sugar cane and sugar beets. Sugar cane the juice of sugar cane and sugar beets. Sugar cane contains up to 20 % by mass saccharose, and sugar contains up to 20 % by mass saccharose, and sugar beets contain up to 17 % by mass saccharose. The beets contain up to 17 % by mass saccharose. The two monosaccharide units present in two monosaccharide units present in -D-saccharose -D-saccharose molecule are molecule are -D-glucose in form of -D-glucose in form of -D--D-glucopyranose and glucopyranose and -D-fructose in form of -D-fructose in form of -D--D-fructofuranose. The glycosidic linkage is not fructofuranose. The glycosidic linkage is not аа (1-4) (1-4) linkage, as was in case with maltose, cellobiose, and linkage, as was in case with maltose, cellobiose, and lactose. It is instead an lactose. It is instead an ,,(1 - 2) glycosidic linkage. (1 - 2) glycosidic linkage. The The ОНОН--group on carbon-2 of D-fructose (the group on carbon-2 of D-fructose (the hemiketal carbon) reacts with the hemiketal carbon) reacts with the ОНОН--group on group on carbon-l of D-glucose (the hemiacetal carbon).carbon-l of D-glucose (the hemiacetal carbon).

Saccharose can be named as 2-O-(α-D-glucopyranosido)-β-D-fructofuranose.

Saccharose, unlike maltose, cellobiose, and Saccharose, unlike maltose, cellobiose, and lactose, is а non-reducing sugar. No helmiacetal or lactose, is а non-reducing sugar. No helmiacetal or hemiketal center is present in the molecule, hemiketal center is present in the molecule, because the glycosidic linkage involves the because the glycosidic linkage involves the reducing ends of both monosaccharides. reducing ends of both monosaccharides. Saccharose, in the solid state and in solution, exists Saccharose, in the solid state and in solution, exists in only one form - there are no in only one form - there are no and and isomers, and isomers, and an open-chain form is not possible. Saccharase, the an open-chain form is not possible. Saccharase, the enzyme needed to break the enzyme needed to break the ,,(1 - 2)(1 - 2) linkage in linkage in saccharose, is present in the human body. Hence saccharose, is present in the human body. Hence saccharose is an easily digested substance.saccharose is an easily digested substance.

• Saccharose hydrolysis (digestion) produces an equimolar Saccharose hydrolysis (digestion) produces an equimolar mixture of glucose and fructose called invert sugar. When mixture of glucose and fructose called invert sugar. When saccharose is cooked with acid-containing foods such as fruits saccharose is cooked with acid-containing foods such as fruits or berries, partial hydrolysis takes place, forming some invert or berries, partial hydrolysis takes place, forming some invert sugar. Jams and jellies prepared in this manner are actually sugar. Jams and jellies prepared in this manner are actually sweeter than the pure saccharose added to the original mixture, sweeter than the pure saccharose added to the original mixture, because one-to-one mixtures of glucose and fructose taste because one-to-one mixtures of glucose and fructose taste sweeter than saccharose.sweeter than saccharose.

• Saccharose is Saccharose is dextrorotatorydextrorotatory. On hydrolysis it gives . On hydrolysis it gives one molecule of glucose and one molecule of fructose. Now one molecule of glucose and one molecule of fructose. Now since fructose is more strongly laevorotatory than the since fructose is more strongly laevorotatory than the dextrorotatory property of glucose, the mixture (product) after dextrorotatory property of glucose, the mixture (product) after hydrolysis will be laevorotatory. hydrolysis will be laevorotatory. This reaction is also as This reaction is also as inversion of sugarinversion of sugar because the dextrorotatory case sugar is because the dextrorotatory case sugar is converted into laevorotatory product due to hydrolysis. The converted into laevorotatory product due to hydrolysis. The mixture of glucose and fructose is called mixture of glucose and fructose is called invert sugarinvert sugar..

dextrorotatory laevorotatory

4. Polysaccharides (glucanes) 4. Polysaccharides (glucanes) А А polysaccharides (glucanes)polysaccharides (glucanes) contains contains

many monosaccharide units bonded to each other many monosaccharide units bonded to each other by glycosidic linkages. The number of by glycosidic linkages. The number of monosaccharide units in polysaccharides varies monosaccharide units in polysaccharides varies from а few hundred to hundreds of thousands. from а few hundred to hundreds of thousands. Polysaccharides are polymers. In some, the Polysaccharides are polymers. In some, the monosaccharides are bonded together in а linear monosaccharides are bonded together in а linear (unbranched) chain. In others, there is extensive (unbranched) chain. In others, there is extensive branching of the chains. Unlike monosaccharides branching of the chains. Unlike monosaccharides and most disaccharides, polysaccharides are not and most disaccharides, polysaccharides are not sweet and do not give positive reaction with sweet and do not give positive reaction with Tollens, Benedict’s, and Feling’s solutions. They Tollens, Benedict’s, and Feling’s solutions. They have limited water solubility because of their size. have limited water solubility because of their size. However, the ОН-groups present in molecule can However, the ОН-groups present in molecule can individually become hydrated by water molecules. individually become hydrated by water molecules. The result is usually а thick colloidal suspension of The result is usually а thick colloidal suspension of the polysaccharide in water. Polysaccharides, the polysaccharide in water. Polysaccharides, such as flour and cornstarch, are often used as such as flour and cornstarch, are often used as thickening agents in sauces, desserts, and gravy.thickening agents in sauces, desserts, and gravy.

Linear and branched structure Linear and branched structure of polysaccharidesof polysaccharides

Although there are many naturally occurring Although there are many naturally occurring polysaccharides, in this section we will focus on only four of polysaccharides, in this section we will focus on only four of them: cellulose, starch, glycogen, and chitin. All play vital them: cellulose, starch, glycogen, and chitin. All play vital roles in living systems - cellulose and starch in plants, roles in living systems - cellulose and starch in plants, glycogen in humans and other animals, and chitin in glycogen in humans and other animals, and chitin in arthropods. arthropods.

Polysaccharides may be divided into two classes: Polysaccharides may be divided into two classes: homopolysaccharideshomopolysaccharides, which are composed of one type of , which are composed of one type of monosaccharide units, and monosaccharide units, and heteropolysaccharidesheteropolysaccharides, which , which contain two or more different types of monosaccharide units.contain two or more different types of monosaccharide units.

Starch, glycogen and cellulose are homoglycans as Starch, glycogen and cellulose are homoglycans as they are made of only glucose and are called glucanes or they are made of only glucose and are called glucanes or glucosanes. Homopolysaccharides which containe only glucosanes. Homopolysaccharides which containe only pentoses called pentosanes, hexoses – hexosanes. On the other pentoses called pentosanes, hexoses – hexosanes. On the other hand, mucopolysaccharides like hyaluronic acid and hand, mucopolysaccharides like hyaluronic acid and chondroitine sulphate are heteroglycanes as they are made up chondroitine sulphate are heteroglycanes as they are made up of different monosaccharide units. of different monosaccharide units. Common formula for pentosanes – Common formula for pentosanes – (C5H8O4)n(C5H8O4)n, for hexosanes , for hexosanes – – (C6H10O5)n(C6H10O5)n..

HomopolysaccharidesHomopolysaccharides

Structure, composition and properties Structure, composition and properties

ofof ccellulose.ellulose.CelluloseCellulose is the most abundant polysaccharide. is the most abundant polysaccharide.

It is the structural component of the cell walls of It is the structural component of the cell walls of plants. Approximately half of all the carbon atoms in plants. Approximately half of all the carbon atoms in the plant kingdom are contained in cellulose the plant kingdom are contained in cellulose molecules. Structurally, cellulose is а linear molecules. Structurally, cellulose is а linear (unbranched) D-glucose polymer in which the (unbranched) D-glucose polymer in which the glucose units are linked by glucose units are linked by (1-4) glycosidic bonds.(1-4) glycosidic bonds.

• At heating with mineral acids cellulose At heating with mineral acids cellulose hydrolyzed by the following scheme:hydrolyzed by the following scheme:

In cellulose glucopyranose In cellulose glucopyranose remainders have linear structure and remainders have linear structure and hydrogen bonds:hydrogen bonds:

Typically, cellulose chains contain about 5000 glucose Typically, cellulose chains contain about 5000 glucose units, which gives macromolecules with molecular masses of about units, which gives macromolecules with molecular masses of about 900,000. Cotton is almost pure cellulose (95 %) and wood is about 900,000. Cotton is almost pure cellulose (95 %) and wood is about 50 % cellulose. Even though it is а glucose polymer, cellulose is 50 % cellulose. Even though it is а glucose polymer, cellulose is not а source of nutrition for human beings. Humans lack the not а source of nutrition for human beings. Humans lack the enzymes capable of catalyzing the hydrolysis of enzymes capable of catalyzing the hydrolysis of (1- 4) linkages (1- 4) linkages in cellulose. Even grazing animals have the enzymes necessary for in cellulose. Even grazing animals have the enzymes necessary for cellulose digestion. However, the intestinal tracts of animals such cellulose digestion. However, the intestinal tracts of animals such as horses, cows, and sheep contain bacteria that produce cellulose, as horses, cows, and sheep contain bacteria that produce cellulose, an enzyme that can hydrolyze an enzyme that can hydrolyze (1- 4) linkages and produce free (1- 4) linkages and produce free glucose from cellulose. Thus grasses and other plant materials are а glucose from cellulose. Thus grasses and other plant materials are а source of nutrition for grazing animals. The intestinal tracts of source of nutrition for grazing animals. The intestinal tracts of termites contain the same microorganisms, which enable termites termites contain the same microorganisms, which enable termites to use wood as their source of food. Microorganisms in the soil can to use wood as their source of food. Microorganisms in the soil can also metabolize cellulose, which makes possible the also metabolize cellulose, which makes possible the biodegradation of dead plants. Despite its nondigestibility, biodegradation of dead plants. Despite its nondigestibility, cellulose is still an important component of а balanced diet. It cellulose is still an important component of а balanced diet. It serves as dietary fiber. Dietary fiber provides the digestive tract serves as dietary fiber. Dietary fiber provides the digestive tract with "bulk" that helps move food through the intestinal tract and with "bulk" that helps move food through the intestinal tract and facilitates the excretion of solid wastes. Cellulose readily absorbs facilitates the excretion of solid wastes. Cellulose readily absorbs water, leading to softer stools and frequent bowel action. Links water, leading to softer stools and frequent bowel action. Links have been found between the length of time stools spend in the have been found between the length of time stools spend in the colon and possible colon cancercolon and possible colon cancer..

High-fiber food may also play а role in weight control. High-fiber food may also play а role in weight control. Obesity is not seen in parts of the world where people eat large Obesity is not seen in parts of the world where people eat large amounts of fiber-rich foods. Many of the weight-loss products amounts of fiber-rich foods. Many of the weight-loss products on the market are composed of bulk-inducing fibers such as on the market are composed of bulk-inducing fibers such as methylcellulose.methylcellulose.

FIGURE. FIGURE. Cellulose microfibrils.Cellulose microfibrils. • Some fibers bind lipids such as cholesterol Some fibers bind lipids such as cholesterol

and carry out them of the body with the and carry out them of the body with the feces. This lowers blood lipid concentrations feces. This lowers blood lipid concentrations and possibly the risk of heart and artery and possibly the risk of heart and artery disease.disease.

Structure, composition and properties ofStructure, composition and properties of sstarch.tarch.

Starch,Starch, like cellulose, is а polysaccharide like cellulose, is а polysaccharide containing only containing only glucose unitsglucose units. It is the storage . It is the storage polysaccharide in plants. If excess of glucose enters polysaccharide in plants. If excess of glucose enters а plant cell, it is converted to starch and stored for а plant cell, it is converted to starch and stored for later use. When the cell cannot get enough glucose later use. When the cell cannot get enough glucose from outside, it hydrolyzes starch to release glucose. from outside, it hydrolyzes starch to release glucose. IodineIodine is often used to test the presence of starch in is often used to test the presence of starch in solution. Starch-containing solutions turn а dark blue solution. Starch-containing solutions turn а dark blue when iodine is added. As starch is broken down when iodine is added. As starch is broken down through acid or enzymatic hydrolysis to glucose through acid or enzymatic hydrolysis to glucose monomers, the blue color disappears. Two different monomers, the blue color disappears. Two different polyglucose polysaccharides can be isolated from polyglucose polysaccharides can be isolated from most starches: amylose and amylopectin. most starches: amylose and amylopectin. AmyloseAmylose, , а straight-chain glucose polymer, usually accounts а straight-chain glucose polymer, usually accounts for 15% — 20% of the starch; for 15% — 20% of the starch; amylopectinamylopectin, а highly , а highly branched glucose polymer, accounts for the branched glucose polymer, accounts for the remaining 80% — 85% of the starch.remaining 80% — 85% of the starch.

In amylose's structure, the glucose units are connected by In amylose's structure, the glucose units are connected by (1- 4) glycosidic linkages.(1- 4) glycosidic linkages.

Starch (amylose) Starch (amylose)

The number of glucose units present in an The number of glucose units present in an amyloseamylose chain chain depends on the source of the starch; 200 – 350 monomer units depends on the source of the starch; 200 – 350 monomer units are usually present. are usually present. AmylopectinAmylopectin, the other polysaccharide in , the other polysaccharide in starch, is similar to amylose, but has а high degree branched starch, is similar to amylose, but has а high degree branched structure in the polymer. А one branch link containe 20-25 structure in the polymer. А one branch link containe 20-25 glucose units. The number of glucose units present in an glucose units. The number of glucose units present in an amylopectin chain consists of 1000 and more units. The branch amylopectin chain consists of 1000 and more units. The branch points involve points involve (1 – 6) linkages:(1 – 6) linkages:

Starch (amylopectin)

Because of the branching, amylopectin has а Because of the branching, amylopectin has а larger average molecular mass than the linear larger average molecular mass than the linear amylose. The average molecular mass of amylose is amylose. The average molecular mass of amylose is 40000 or more; it is 1-6 mln. for amylopectin. Note 40000 or more; it is 1-6 mln. for amylopectin. Note that all of the glycosidic linkages in starch (both that all of the glycosidic linkages in starch (both amylose and amylopectin) are of the amylose and amylopectin) are of the -type. In -type. In amylose, they are all amylose, they are all (1 - 4); in amylopectin, both (1 - 4); in amylopectin, both (1 -4) and (1 -4) and (1 -6) linkages are present. Because а (1 -6) linkages are present. Because а linkages can be broken through hydrolysis within the linkages can be broken through hydrolysis within the human digestive tract (with the help of the enzyme human digestive tract (with the help of the enzyme amylase), starch has nutritional value for humans. amylase), starch has nutritional value for humans. The starches present in potatoes and cereal grains The starches present in potatoes and cereal grains (wheat, rice, corn, etc.) account for approximately (wheat, rice, corn, etc.) account for approximately two-thirds of the world' s food consumption.two-thirds of the world' s food consumption.Fermentayion hydrolysis of starch is shown below:Fermentayion hydrolysis of starch is shown below:

Glycogen, chitin.Glycogen, chitin.Glycogen,Glycogen, like cellulose and starch, is а polysaccharide like cellulose and starch, is а polysaccharide

containing only containing only glucose unitsglucose units. It is the glucose storage . It is the glucose storage polysaccharide in humans and animals. Its function is thus similar polysaccharide in humans and animals. Its function is thus similar to that of starch in plants, and it is sometimes referred to as animal to that of starch in plants, and it is sometimes referred to as animal starch. Liver cells and muscle cells are the storage sites for starch. Liver cells and muscle cells are the storage sites for glycogen in humans. Glycogen has а structure glycogen in humans. Glycogen has а structure similarsimilar to that of to that of amylopectinamylopectin; all glycosidic linkages are of the ; all glycosidic linkages are of the -type-type, and both , and both (1-4) and (1-6)(1-4) and (1-6) linkages are present. Glycogen and amylopectin linkages are present. Glycogen and amylopectin differ in the number of glucose units between branches and the differ in the number of glucose units between branches and the total number of glucose units present in а molecule. Glycogen is total number of glucose units present in а molecule. Glycogen is about three times more highly branched than amylopectin, and it is about three times more highly branched than amylopectin, and it is much larger, with а molar mass. А one branch link containe much larger, with а molar mass. А one branch link containe 8-128-12 glucose units, rare – glucose units, rare – 2- 42- 4. When excess of glucose is present in the . When excess of glucose is present in the blood (normally from eating too much starch), the liver and muscle blood (normally from eating too much starch), the liver and muscle tissue convert the excess of glucose to glycogen, which is then tissue convert the excess of glucose to glycogen, which is then stored in these tissues. Whenever the glucose blood level drops stored in these tissues. Whenever the glucose blood level drops (from exercise, fasting, or normal activities), some stored glycogen (from exercise, fasting, or normal activities), some stored glycogen is hydrolyzed back to glucose. These two opposing processes are is hydrolyzed back to glucose. These two opposing processes are called glycogenesis and glycogenolysis, the formation and called glycogenesis and glycogenolysis, the formation and decomposition of glycogen, respectively.decomposition of glycogen, respectively.

Glycogen is an ideal storage form for glucose. The Glycogen is an ideal storage form for glucose. The large size of these macromolecules prevents them from large size of these macromolecules prevents them from diffusing out of cells. Also, conversion of glucose to glycogen diffusing out of cells. Also, conversion of glucose to glycogen reduces osmotic pressure. Cells would burst because of reduces osmotic pressure. Cells would burst because of increased osmotic pressure if all of the glucose in glycogen increased osmotic pressure if all of the glucose in glycogen were present in cells in free form. High concentrations of were present in cells in free form. High concentrations of glycogen in а cell sometimes cases precipitate or crystallize glycogen in а cell sometimes cases precipitate or crystallize into glycogen granules. These granules are discernible in into glycogen granules. These granules are discernible in photographs of cells under electron microscope magnification. photographs of cells under electron microscope magnification. The glucose polymers amylose, amylopectin, and glycogen The glucose polymers amylose, amylopectin, and glycogen compare as follows in molecular size and degree of branching:compare as follows in molecular size and degree of branching:

• Amylose:Amylose: Up to 1000 glucose units; no branching Up to 1000 glucose units; no branching• Amylopectin:Amylopectin: Up to 100,000 glucose units; branch points Up to 100,000 glucose units; branch points

every 20-25 glucose unitsevery 20-25 glucose units• Glycogen:Glycogen: Up to 1,000,000 glucose units; branch points every Up to 1,000,000 glucose units; branch points every

8-12 glucose units8-12 glucose units

FIGURE. FIGURE. Structure of amylopectine ( Structure of amylopectine (аа), glycogen (b) ), glycogen (b)

DextranesDextranes• Dextranes Dextranes have bacterial origin, contain remainders of have bacterial origin, contain remainders of αα--

D-glucopyranoseD-glucopyranose. Dextranes obtain from saccharose at . Dextranes obtain from saccharose at the present of bacterium (Leuconostoc mesenteroides). The the present of bacterium (Leuconostoc mesenteroides). The main type of bond is main type of bond is αα-1,6-glycosidic bond, in place of -1,6-glycosidic bond, in place of branching – branching – αα-1,4- and -1,4- and αα-1,3-glycosidic bonds. -1,3-glycosidic bonds. The average The average molecular mass of dextranes is few millions. Partly hydrolyzed dextranes molecular mass of dextranes is few millions. Partly hydrolyzed dextranes (m. m. – 40000-800000) use in pharmacy as plasmasubstitute (m. m. – 40000-800000) use in pharmacy as plasmasubstitute (“Polyglucin”, “Reopolyglucin”). (“Polyglucin”, “Reopolyglucin”).

InulineInuline• Inuline – reserve polysaccharide, present Inuline – reserve polysaccharide, present

in plants. Inuline has linear structure and in plants. Inuline has linear structure and consists of remainders of consists of remainders of ββ-D--D-fructofuranosefructofuranose, joined by 2,1-, joined by 2,1-glycosidic bonds, in the end of inuline is glycosidic bonds, in the end of inuline is αα-D-glucopyranose remainder (like -D-glucopyranose remainder (like saccharose). Msaccharose). Molecular mass of inuline is olecular mass of inuline is up to 6000. Use for obtaining of D-up to 6000. Use for obtaining of D-fructose.fructose.

Pectin compoundsPectin compounds

• Pectin compounds (pectins) – Pectin compounds (pectins) – polysaccharides consist of polysaccharides consist of polygalacturonic acid, which contain polygalacturonic acid, which contain remainders of remainders of αα-D-galacturonic -D-galacturonic acidacid joined by 1,4-glycosidic bonds. joined by 1,4-glycosidic bonds. Part of carboxyl grups present in Part of carboxyl grups present in appearance of methyl ether. Water appearance of methyl ether. Water solutions of pectins form stable gels. solutions of pectins form stable gels. Pectins have antiulcer properties.Pectins have antiulcer properties.

ChitinChitin is а polysaccharide that is is а polysaccharide that is similar similar toto cellulosecellulose in both function and structure. Its in both function and structure. Its function is to give rigidity to the exoskeletons function is to give rigidity to the exoskeletons of crabs, lobsters, shrimp, insects, and other of crabs, lobsters, shrimp, insects, and other arthropods. It also occurs in the cell walls of arthropods. It also occurs in the cell walls of fungi. Structurally, chitin is а linear polymer fungi. Structurally, chitin is а linear polymer (no branching) with all (no branching) with all (1- 4)(1- 4) glycosidic glycosidic linkages, as in cellulose. Chitin differs from linkages, as in cellulose. Chitin differs from cellulose in that the monosaccharide present is cellulose in that the monosaccharide present is an an N-acetylamino derivative of D-glucose.N-acetylamino derivative of D-glucose.

HeteropolysaccharidesHeteropolysaccharides.. Unlike all the polysaccharides we have discussed up to Unlike all the polysaccharides we have discussed up to

this point, mucopolysaccharides are heteropolysaccharides this point, mucopolysaccharides are heteropolysaccharides rather than homopolysaccharides. rather than homopolysaccharides.

• MucopolysaccharidesMucopolysaccharides are compounds that occur in are compounds that occur in connective tissue associated with joints in animals and connective tissue associated with joints in animals and humans. Their function is primarily that of lubrication, а humans. Their function is primarily that of lubrication, а necessary requirement if movement is to occur. The name necessary requirement if movement is to occur. The name mucopolysaccharide comes from the highly viscous, mucopolysaccharide comes from the highly viscous, gelatinous (mucus-like) consistency of these substances in gelatinous (mucus-like) consistency of these substances in aqueous solution.aqueous solution.

• А А heteropolysaccharide heteropolysaccharide is а polysaccharide in which more is а polysaccharide in which more than one (usually two) type of monosaccharide unit is present.than one (usually two) type of monosaccharide unit is present.One of the most common mucopolysaccharides is One of the most common mucopolysaccharides is hyaluronic hyaluronic acidacid, а heteropolysaccharide in which the following two , а heteropolysaccharide in which the following two glucose derivatives alternate in the structure.glucose derivatives alternate in the structure.

It is а highly viscous substance and has а molecular weight It is а highly viscous substance and has а molecular weight in several hundred millions. in several hundred millions. Hyaluronic acidHyaluronic acid is а principal is а principal component of the ground substance of connective tissue. Among component of the ground substance of connective tissue. Among other places it is found in skin, synovial fluid, vitreous hemour of other places it is found in skin, synovial fluid, vitreous hemour of the eye, and umbilical cord. It exercises а cementing function in the the eye, and umbilical cord. It exercises а cementing function in the tissues and capillary walls, and forms а coating gel round the ovum. tissues and capillary walls, and forms а coating gel round the ovum. It accounts for about 80% of the viscosity of synovial fluid which It accounts for about 80% of the viscosity of synovial fluid which contains about 0. 02 – 0.05% of hyaluronate. Repeat part of contains about 0. 02 – 0.05% of hyaluronate. Repeat part of hyaluronic acid is hyaluronic acid is D-glucuronic acid and N-acetyl-D-D-glucuronic acid and N-acetyl-D-glucosamineglucosamine joined by joined by ββ--1,31,3-glycosidic bond, between -glycosidic bond, between disaccharide fragments – disaccharide fragments – ββ-1,4-1,4. Molecular mass of . Molecular mass of hyaluronic acid hyaluronic acid is from 1600 to 6400.is from 1600 to 6400.

(1,4)-O-(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy--D-glucopyranose.-D-glucopyranose.

Hyaluronic acidHyaluronic acid is split up by the enzyme is split up by the enzyme hyalurosidase into а number of small molecule. If hyalurosidase into а number of small molecule. If fluid containing this enzyme is injected into а tissue it fluid containing this enzyme is injected into а tissue it spreads rapidly, from the site of injection and thus spreads rapidly, from the site of injection and thus this enzyme is sometimes referred as the this enzyme is sometimes referred as the “spreading “spreading factor”.factor”. It is found in relatively high concentration in It is found in relatively high concentration in the testis and seminal fluid, in the venoms of certain the testis and seminal fluid, in the venoms of certain snakes and insects, and in some bacteria. The enzyme snakes and insects, and in some bacteria. The enzyme also has а physiological role in fertilization. The also has а physiological role in fertilization. The sperm is rich in the enzyme and the former can thus sperm is rich in the enzyme and the former can thus advance better in the cervical canal and finally advance better in the cervical canal and finally penetrates the ovumpenetrates the ovum. .

Chondroitin sulfate.Chondroitin sulfate. It has similar structure as hyaluronic It has similar structure as hyaluronic acid with the difference that the N-acetyl-D-glucosamine unit of the acid with the difference that the N-acetyl-D-glucosamine unit of the molecule is replaced by N-acetyl-D-galactosamine unit with molecule is replaced by N-acetyl-D-galactosamine unit with sulphate group. Repeat part of chondroitin sulphate is D-glucuronic sulphate group. Repeat part of chondroitin sulphate is D-glucuronic acid and N-acetyl-D-galactosamine which contains sulfate group. acid and N-acetyl-D-galactosamine which contains sulfate group. Inside of disaccharide fragment is Inside of disaccharide fragment is ββ-1,3-glycosidic bond; between -1,3-glycosidic bond; between fragments – fragments – ββ-1,4. Sulfate group forms ether bond with hydroxyl -1,4. Sulfate group forms ether bond with hydroxyl group of group of N-acetyl-D-galactosamine in location 4 (N-acetyl-D-galactosamine in location 4 (chondroitin-4-chondroitin-4-sulfatesulfate) or in location 6 () or in location 6 (chondroitin-6-sulfatechondroitin-6-sulfate). Chondroitin ). Chondroitin sulfates are found in cartilage, bone, heart valves, tendons and sulfates are found in cartilage, bone, heart valves, tendons and cornea.cornea.

(1,4)-O-(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo---D-galactopyranose.D-galactopyranose.

Hydrocarbon chains of chondroitin-4-sulfate chondroitin-4-sulfate contain up to 150 disaccharides remainders, contain up to 150 disaccharides remainders, joined in organism by O-glycosidic bonds with joined in organism by O-glycosidic bonds with hydroxyl groups of aminoacid remainders. hydroxyl groups of aminoacid remainders.

Dermatan sulfateDermatan sulfate. (Varying amounts of D-. (Varying amounts of D-glucuronic acid may be present. Concentration glucuronic acid may be present. Concentration increases during aging process.)increases during aging process.)

(1,4)-O-(1,4)-O--L-idopyranosyluronic acid-(1,3)-2--L-idopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-4-O-sulfo-acetamino-2-dezoxy-4-O-sulfo--D--D-

galactopyranose. galactopyranose.

Heparin.Heparin. It is naturally occurring anticoagulant found It is naturally occurring anticoagulant found mainly in the liver, and also in lung, spleen, kidney and intestinal mainly in the liver, and also in lung, spleen, kidney and intestinal mucosa. It prevents blood clotting by inhibiting the prothrombin-mucosa. It prevents blood clotting by inhibiting the prothrombin-thrombin conversion and thus eliminating the thrombin effect on thrombin conversion and thus eliminating the thrombin effect on fibrinogen. Repeat part of heparin consists of fibrinogen. Repeat part of heparin consists of D-glucosaminD-glucosamin and and uronic aciduronic acid, joined by , joined by αα-1,4-glycosidic bonds. As uronic acid in -1,4-glycosidic bonds. As uronic acid in heparin present heparin present L-iduronic acidL-iduronic acid or, very rare, D-glucuronic acid. or, very rare, D-glucuronic acid. Remainders of glucosamine and L-iduronic acid partly sulfonated.Remainders of glucosamine and L-iduronic acid partly sulfonated. Molecular mass of Molecular mass of heparin is 16000-20000.heparin is 16000-20000.

(1,4)-O-(1,4)-O--D-idupyranosyluronic acid-2-O-sulfo--D-idupyranosyluronic acid-2-O-sulfo-(1,4)-2-sulfamino-2-dezoxy-6-O-sulfo-(1,4)-2-sulfamino-2-dezoxy-6-O-sulfo--D--D-glucopyranoseglucopyranose

5. 5. Glycoconjugates.Glycoconjugates. The compounds that result from the covalent The compounds that result from the covalent

linkages of carbohydrate molecules to both proteins linkages of carbohydrate molecules to both proteins and lipids are collectively known as the and lipids are collectively known as the glycoconjugatesglycoconjugates. These substances have profound . These substances have profound effects on the function of individual cells, as well as effects on the function of individual cells, as well as the cell-cell interactions of multicellular organisms. the cell-cell interactions of multicellular organisms. There are two classes of carbohydrate-protein There are two classes of carbohydrate-protein conjugate: conjugate: proteoglycans proteoglycans and and glycoproteinsglycoproteins. . Although both molecular types contain Although both molecular types contain сагсагbohydrate bohydrate and protein, their structures and functions appear, in and protein, their structures and functions appear, in general, to be substantially different. The general, to be substantially different. The glycolipidsglycolipids, , which are oligosaccharide-containing lipid molecules, which are oligosaccharide-containing lipid molecules, are found predominantly on the outer surface of are found predominantly on the outer surface of plasma membranes.plasma membranes.

ProteoglycansProteoglycans are distinguished from the are distinguished from the common glycoproteins by their extremely high common glycoproteins by their extremely high carbohydrate content, which may constitute as carbohydrate content, which may constitute as much as 95% of the dry weight of such much as 95% of the dry weight of such molecules. These molecules are found molecules. These molecules are found predominantly in the extracellular matrix predominantly in the extracellular matrix (intercellular material) of tissues. All (intercellular material) of tissues. All proteoglycans contain GAG chains. The GAG proteoglycans contain GAG chains. The GAG chains are linked to protein molecules (known chains are linked to protein molecules (known as core proteins) by N- and O-glycosidic as core proteins) by N- and O-glycosidic linkages. The diversity of proteoglycans is linkages. The diversity of proteoglycans is аа result of both the number of different core result of both the number of different core proteins and the large variety of different classes proteins and the large variety of different classes and length of the carbohydrate chains.and length of the carbohydrate chains.

FigFig.. Proteoglycan structure Proteoglycan structure

Because proteoglycans contain large numbers of GAGs, Because proteoglycans contain large numbers of GAGs, which are polyanions, large volumes of water and cations are which are polyanions, large volumes of water and cations are trapped within their structure. As trapped within their structure. As аа result, proteoglycan result, proteoglycan molecules occupy space that is thousands of times bigger that of molecules occupy space that is thousands of times bigger that of аа densely packed molecule of the same mass. Proteoglycans densely packed molecule of the same mass. Proteoglycans contribute support and elasticity to tissues in which they occur. contribute support and elasticity to tissues in which they occur. Consider, for example, the strength, flexibility, and resilience of Consider, for example, the strength, flexibility, and resilience of cartilage. The structural diversity of proteoglycans allows them cartilage. The structural diversity of proteoglycans allows them to serve to serve аа variety of structural and functional roles in living variety of structural and functional roles in living organisms. Proteoglycans are particularly abundant in the organisms. Proteoglycans are particularly abundant in the extracellular matrix of connective tissue. Together with matrix extracellular matrix of connective tissue. Together with matrix proteins such as collagen, fibrinogen and laminin, they form an proteins such as collagen, fibrinogen and laminin, they form an organized meshwork that provides strength and support to organized meshwork that provides strength and support to multicellular tissues. Proteoglycans are also present at the multicellular tissues. Proteoglycans are also present at the surface of cells, where they are directly bound with the plasma surface of cells, where they are directly bound with the plasma membrane. Although the function of these latter molecules is membrane. Although the function of these latter molecules is not yet clear, the suggestion has been made that they play an not yet clear, the suggestion has been made that they play an important role in membrane structure and cell-cell interactions. important role in membrane structure and cell-cell interactions.

АА number of number of genetic diseasesgenetic diseases associated with associated with proteoglycan metabolism, known as proteoglycan metabolism, known as mucopolysaccharidosesmucopolysaccharidoses, , have been identified. Because proteoglycans are constantly have been identified. Because proteoglycans are constantly being synthesized and degraded, their excessive accumulation being synthesized and degraded, their excessive accumulation (due to missing or defective lyzosomal enzymes) has very (due to missing or defective lyzosomal enzymes) has very serious consequences. For example, in Hurler's syndrome, an serious consequences. For example, in Hurler's syndrome, an autosomal recessive disorder (autosomal recessive disorder (аа disease type in which one copy disease type in which one copy of the defective gene is inherited from each parent), deficiency of the defective gene is inherited from each parent), deficiency of of аа specific enzyme results in accumulation of dermatan specific enzyme results in accumulation of dermatan sulfate. Symptoms include mental retardation, skeletal sulfate. Symptoms include mental retardation, skeletal deformity, and early childhood death. deformity, and early childhood death. GlycoproteinsGlycoproteins are are commonly defined as proteins that are covalently linked to commonly defined as proteins that are covalently linked to carbohydrate through carbohydrate through O- or N-linkagesO- or N-linkages. The carbohydrate . The carbohydrate contain of glycoprotein varies from 1% to over 85% of total contain of glycoprotein varies from 1% to over 85% of total weight. The types of carbohydrate that are founded include weight. The types of carbohydrate that are founded include monosaccharides and disaccharides such as those attached to the monosaccharides and disaccharides such as those attached to the structural protein collagen and branched oligosaccharides on structural protein collagen and branched oligosaccharides on plasma glycoproteins. Although the glycoproteins are plasma glycoproteins. Although the glycoproteins are sometimes considered to include the proteoglycans, there appear sometimes considered to include the proteoglycans, there appear to be sufficient structural reasons to examine them separately. to be sufficient structural reasons to examine them separately.

These substances include glycoproteins of These substances include glycoproteins of uronic acids, sulfate groups and disaccharide uronic acids, sulfate groups and disaccharide repeating units that are typical for proteoglycans. The repeating units that are typical for proteoglycans. The carbohydrate groups of glycoproteins are linked to carbohydrate groups of glycoproteins are linked to the polypeptide by either (1) an N-glycosidic linkage the polypeptide by either (1) an N-glycosidic linkage between N-acetylglucosamine (GlcNAc) and the between N-acetylglucosamine (GlcNAc) and the aminoacid asparagine (Asn) or (2) an O-glycosidic aminoacid asparagine (Asn) or (2) an O-glycosidic linkage between N-acetylgalactosamine (GalNAc) linkage between N-acetylgalactosamine (GalNAc) and the hydroxyl group of the and the hydroxyl group of the ааminoacids serine (Ser) minoacids serine (Ser) or threonine (Thr). The former glycoprotein class is or threonine (Thr). The former glycoprotein class is sometimes referred to as asparagine-linked; the latter sometimes referred to as asparagine-linked; the latter is often called mucin-type. is often called mucin-type.

• Asparagine-linked carbohydratesAsparagine-linked carbohydrates. As was . As was mentioned previously, three structural forms of mentioned previously, three structural forms of asparagine-linked oligosaccharide occur in asparagine-linked oligosaccharide occur in glycoproteins: high- mannose, complex, and hybrid. glycoproteins: high- mannose, complex, and hybrid. High-mannose type is composed of GlcNAc and High-mannose type is composed of GlcNAc and mannose. Complex-type may contain fructose, mannose. Complex-type may contain fructose, galactose, and sialic acid in addition to GlcNAc and galactose, and sialic acid in addition to GlcNAc and mannose. Hybrid-type oligosaccharides contain mannose. Hybrid-type oligosaccharides contain features of both complex and high-mannose-type features of both complex and high-mannose-type species. Despite these differences, the core structure species. Despite these differences, the core structure of all N-linked of all N-linked oligosaccharides is the same. This oligosaccharides is the same. This core, which is constructed on core, which is constructed on аа membrane-bound membrane-bound lipid molecule, is covalently linked to asparagine lipid molecule, is covalently linked to asparagine during protein synthesis. during protein synthesis. Several additional reactions, Several additional reactions, which occur within the lumen of the endoplasmic which occur within the lumen of the endoplasmic reticulum and the Golgi complex, result in the final reticulum and the Golgi complex, result in the final N-linked oligosaccharide structures.N-linked oligosaccharide structures.

Mucin-type carbohydrate Mucin-type carbohydrate While all N-linked While all N-linked oligosaccharides are bound to protein via GlcNAc-Asn, the oligosaccharides are bound to protein via GlcNAc-Asn, the linking groups of O-glycosidic oligosaccharides are of several linking groups of O-glycosidic oligosaccharides are of several types. The most common of these is GalNAc-Ser (or GalNAc-types. The most common of these is GalNAc-Ser (or GalNAc-Thr). Considerable mucin-type carbohydrate unit is Thr). Considerable mucin-type carbohydrate unit is disaccharide such as Gal-1,3-GalNAc, found in the antifreeze disaccharide such as Gal-1,3-GalNAc, found in the antifreeze glycoprotein of antarctic fish (Figure), to the complex glycoprotein of antarctic fish (Figure), to the complex oligosaccharides of blood groups such as those of the ABO oligosaccharides of blood groups such as those of the ABO system.system.

Fig. Antifreeze glycoprotein structure.Fig. Antifreeze glycoprotein structure.

6. Lipids6. LipidsLipids differ from the other classes of naturally

occurring biomolecules (carbohydrates, proteins, and nucleic acids), they are more soluble in non- or weakly polar solvents (diethyl ether, hexane, dichloromethane) than in water. They include a variety of structural types, a collection of which is introduced in this chapter. In spite of the number of different structural types, lipids share a common biosynthetic origin in that they are ultimately derived from glucose. During one stage of carbohydrate metabolism, called glycolysis, glucose is converted to lactic acid. Pyruvic acid is an intermediate product.

Classification of lipidsClassification of lipids

• Classification:Classification: Lipids can be divided into two major classes on the Lipids can be divided into two major classes on the basis of whether they undergo hydrolysis reactions in alkaline (basic) basis of whether they undergo hydrolysis reactions in alkaline (basic) solution. solution. Saponifiable lipidsSaponifiable lipids can be hydrolyzed under alkaline can be hydrolyzed under alkaline conditions to yield salts of fatty acids. conditions to yield salts of fatty acids. Nonsaponifiable lipidsNonsaponifiable lipids do do not undergo hydrolysis reactions in alkaline solution.not undergo hydrolysis reactions in alkaline solution.

• The basis of the nature of the products obtained on hydrolysis lipids The basis of the nature of the products obtained on hydrolysis lipids are mainly divided into three type: simple, compound and derived are mainly divided into three type: simple, compound and derived lipids.lipids.

• 1. Simple lipids.1. Simple lipids. These are esters of fatty acids and alcohols and These are esters of fatty acids and alcohols and thus on hydrolysis give fatty acids and alcohols. They may be of two thus on hydrolysis give fatty acids and alcohols. They may be of two types.types.

• а) Fats and oils. These are esters of fatty acids and glycerol (а а) Fats and oils. These are esters of fatty acids and glycerol (а trihydric alcohol). These are also known as glycerides.trihydric alcohol). These are also known as glycerides.

• b) Waxes. These are esters of long-chain fatty acids and long-chain b) Waxes. These are esters of long-chain fatty acids and long-chain monohydric alcohols or sterols.monohydric alcohols or sterols.

• 2 Compound lipids.2 Compound lipids. Compound lipids are esters of fatty acids and Compound lipids are esters of fatty acids and alcohols in combination with other compound and thus on hydrolysis alcohols in combination with other compound and thus on hydrolysis give fatty acids, alcohol and other compounds. On the basis of the give fatty acids, alcohol and other compounds. On the basis of the nature of the other group, compound lipids may again be of following nature of the other group, compound lipids may again be of following types.types.

• а) Phospholipids. These are fat like compounds containing а) Phospholipids. These are fat like compounds containing phosphoric acid and а nitrogen base.phosphoric acid and а nitrogen base.

• b) Glycolipids. These are compounds containing а fatty acid, а b) Glycolipids. These are compounds containing а fatty acid, а carbohydrate, а complex alcohol, and nitrogen, but nо phosphorus.carbohydrate, а complex alcohol, and nitrogen, but nо phosphorus.

• 3. Derived lipids.3. Derived lipids. These compounds although do not contain an These compounds although do not contain an ester linkage but are obtained by the hydrolysis of simple and ester linkage but are obtained by the hydrolysis of simple and compound lipids. They may be fatty acids, alcohols and sterols.compound lipids. They may be fatty acids, alcohols and sterols.

Lipids are organic compounds, found in living Lipids are organic compounds, found in living organisms, that are soluble in nonpolar organic solvents. organisms, that are soluble in nonpolar organic solvents. Because compounds are classified as lipids on the basis of a Because compounds are classified as lipids on the basis of a physical property— their solubility in an organic solvent—physical property— their solubility in an organic solvent—rather than as a result of their structures, lipids have a rather than as a result of their structures, lipids have a variety of structures and functions, as the variety of structures and functions, as the following following examples illustrate:examples illustrate:

Functions of lipidsFunctions of lipids – – The most important role of lipids is as а fuel. Much of The most important role of lipids is as а fuel. Much of

the carbohydrates of the diet are converted to fat which the carbohydrates of the diet are converted to fat which is stored in various tissues and utilised at the time of is stored in various tissues and utilised at the time of requirement. Thus fat may be the major source of energy requirement. Thus fat may be the major source of energy for many tissues. Actually, in some respects lipids (fats) for many tissues. Actually, in some respects lipids (fats) are even superior to carbohydrates as source of energy.are even superior to carbohydrates as source of energy.

– – Fatty acids with their flexible backbones can be stored Fatty acids with their flexible backbones can be stored in а much more compact form than the highly spatially in а much more compact form than the highly spatially oriented and rigid glycogen structure. Thus fat storage oriented and rigid glycogen structure. Thus fat storage provides economy in both weight and space. In addition provides economy in both weight and space. In addition to the above three reasons there are two other reasons to the above three reasons there are two other reasons for fat storage as an excellent form of energy.for fat storage as an excellent form of energy.

– – As it is insoluble in water, it has been carried to the fat As it is insoluble in water, it has been carried to the fat depots by the specialised transport proteins in the depots by the specialised transport proteins in the plasma.plasma.

– – It remains as а stable and fixed reserve of energy until It remains as а stable and fixed reserve of energy until mobilized by enzymes which hydrolyse it to glycerol and mobilized by enzymes which hydrolyse it to glycerol and fatty acids. The enzymes are under the control of various fatty acids. The enzymes are under the control of various hormones and are activated under conditions where the hormones and are activated under conditions where the body is involved in increased energy expenditure.body is involved in increased energy expenditure.

– – Fat may also provide padding to protect the Fat may also provide padding to protect the internal organs. Brain and nervous tissue are rich in internal organs. Brain and nervous tissue are rich in certain lipids, а fact which indicates the importance certain lipids, а fact which indicates the importance of these compounds to life.of these compounds to life.

– – Some compounds derived from lipids are Some compounds derived from lipids are important building blocks of biologically active important building blocks of biologically active materials; е.g. acetic acid can be used by the body materials; е.g. acetic acid can be used by the body to synthesize cholesterol and related compounds to synthesize cholesterol and related compounds (hormones).(hormones).

– – Lipoproteins are constituents of cell walls. The Lipoproteins are constituents of cell walls. The lipids present in lipoproteins constituting the cell lipids present in lipoproteins constituting the cell walls are of the types of phospholipids. Since lipids walls are of the types of phospholipids. Since lipids are water insoluble they act as ideal barrier for are water insoluble they act as ideal barrier for preventing water soluble materials from passing preventing water soluble materials from passing freely between the intra- and extra-cellular fluids.freely between the intra- and extra-cellular fluids.

– – One more important function of dietary lipids is One more important function of dietary lipids is that of supplying the so-called essential fatty acids that of supplying the so-called essential fatty acids although there are several functions (essential fatty although there are several functions (essential fatty acids (EFA), none of them are well defined.acids (EFA), none of them are well defined.

Fats and oils are naturally occurring mixtures of triacylglycerols, also called triglycerides.They differ in that fats are solids at room temperature and oils are liquids. We generally ignore this distinction and refer to both groups as fats. Triacylglycerols are built on a glycerol framework.

Simple triacylglycerines include similar fatty acids , mixed – different. All three acyl groups in a triacylglycerol may be the same, all three may be different, or one may be different from the other two.

Nomenclature, methods of Nomenclature, methods of getting of fatsgetting of fats

Methods of getting:Methods of getting:

1.1. O-acylation of alcohols;O-acylation of alcohols;

2.2. Allocation from plants: melting out, pressing or Allocation from plants: melting out, pressing or extraction by organic solvents.extraction by organic solvents.

For simple glycerides the name is made up of the name of the alcohol (glycerol) or its radical (glyceryl) and the name of the acid; or the name of the acid concerned is changed to suffix in. For mixed glycerides, the position and names of the acid groups are specified by Greek letters α, β, α’ or by the numerals 1, 2 and 3.

Fatty acids Fatty acids are carboxylic acids with long are carboxylic acids with long hydrocarbon chains. Because they are synthesized hydrocarbon chains. Because they are synthesized from acetate, a compound with two carbon atoms, from acetate, a compound with two carbon atoms, most naturally occurring fatty acids contain an even most naturally occurring fatty acids contain an even number of carbon atoms and are unbranched. Fatty number of carbon atoms and are unbranched. Fatty acids can be saturated with hydrogen (and therefore acids can be saturated with hydrogen (and therefore have no carbon–carbon double bonds) or unsaturated have no carbon–carbon double bonds) or unsaturated (have carbon–carbon double bonds). Fatty acids with (have carbon–carbon double bonds). Fatty acids with more than one double bond are called more than one double bond are called polyunsaturated fatty acidspolyunsaturated fatty acids. Double bonds in . Double bonds in naturally occurring unsaturated fatty acids are never naturally occurring unsaturated fatty acids are never conjugated — they are always separated by one conjugated — they are always separated by one methylene group. The physical properties of a fatty methylene group. The physical properties of a fatty acid depend on the length of the hydrocarbon chain acid depend on the length of the hydrocarbon chain and the degree of unsaturation. As expected, the and the degree of unsaturation. As expected, the melting points of saturated fatty acids increase with melting points of saturated fatty acids increase with increasing molecular weight because of increased increasing molecular weight because of increased Van-der-Waals interactions between the moleculesVan-der-Waals interactions between the molecules

The most widespread fatty The most widespread fatty acids in natural oils and fats:acids in natural oils and fats:

Double bonds are rigid structures, unsaturared acid Double bonds are rigid structures, unsaturared acid molecules that contain them can occur in two isomeric forms: molecules that contain them can occur in two isomeric forms: ciscis and and transtrans. In cis-isomers, for example, similar or identical groups . In cis-isomers, for example, similar or identical groups are on the same side of double bond (a). When such groups are on are on the same side of double bond (a). When such groups are on opposite sides of a double bond, the molecule is said to be a trans-opposite sides of a double bond, the molecule is said to be a trans-isomer (b):isomer (b):

The double bonds in unsaturated fatty acids generally have the The double bonds in unsaturated fatty acids generally have the cis cis configurationconfiguration. This configuration produces a bend in the molecules, which . This configuration produces a bend in the molecules, which prevents them from packing together as tightly as fully saturated fatty prevents them from packing together as tightly as fully saturated fatty acids. As a result, unsaturated fatty acids have fewer intermolecular acids. As a result, unsaturated fatty acids have fewer intermolecular interactions and, therefore, lower melting points than saturated fatty acids interactions and, therefore, lower melting points than saturated fatty acids with comparable molecular weights . The melting points of the unsaturated with comparable molecular weights . The melting points of the unsaturated fatty acids decrease as the number of double bonds increases. For example, fatty acids decrease as the number of double bonds increases. For example, an 18-carbon fatty acid melts at 69 °C if it is saturated, at 13 °C if it has an 18-carbon fatty acid melts at 69 °C if it is saturated, at 13 °C if it has one double bond, at if it has two -5 °C o double bonds, and at -11 °C if it one double bond, at if it has two -5 °C o double bonds, and at -11 °C if it has three double bonds.has three double bonds.

TriacylglycerolsTriacylglycerols, also called triglycerides, , also called triglycerides, are compounds in which the three OH-groups of are compounds in which the three OH-groups of glycerol are esterified with fatty acids. If the glycerol are esterified with fatty acids. If the three fatty acid components of a triacylglycerol three fatty acid components of a triacylglycerol are the same, the compound is called a are the same, the compound is called a simple simple triacylglyceroltriacylglycerol. . Mixed triacylglycerolsMixed triacylglycerols, on the , on the other hand, contain two or three different fatty other hand, contain two or three different fatty acid components and are more common than acid components and are more common than simple triacylglycerols. Not all triacylglycerol simple triacylglycerols. Not all triacylglycerol molecules from a single source are necessarily molecules from a single source are necessarily identical; substances such as lard and olive oil, identical; substances such as lard and olive oil, for example, are mixtures of several different for example, are mixtures of several different triacylglycerols.triacylglycerols.

Triacylglycerols that are solids or semisolids at room temperature are called fats. Fats are usually obtained from animals and are composed largely of triacylglycerols with either saturated fatty acids or fatty acids with only one double bond. The saturated fatty acid tails pack closely together, giving the triacylglycerols relatively high melting points, causing them to be solids at room temperature. Liquid triacylglycerols are called oils. Oils typically come from plant products such as corn, soybeans, olives, and peanuts. They are composed primarily of triacylglycerols with unsaturated fatty acids that cannot pack tightly together. Consequently, they have relatively low melting points, causing them to be liquids at room temperature.

HydrolysisHydrolysis of а of а triacylglycerol triacylglycerol

HydrolysisHydrolysis of а triacylglycerol is the of а triacylglycerol is the reverse of the esterification reaction reverse of the esterification reaction by which it wet formed. Complete by which it wet formed. Complete hydrolysis of а triacylglycerol hydrolysis of а triacylglycerol molecule always gives one glycerol molecule always gives one glycerol molecule and three fatty acid molecule and three fatty acid molecules as products.molecules as products.

7. Chemical properties of 7. Chemical properties of fats fats

1). 1). Hydrolysis of fats with alkaliHydrolysis of fats with alkali (e.g., sodium hydroxide) yields salts of the (e.g., sodium hydroxide) yields salts of thefatty acids, and those of the alkali metals, such as sodium or potassium, are fatty acids, and those of the alkali metals, such as sodium or potassium, are useuseigig as soaps as soaps. Another name of this reaction – “saponification”. Another name of this reaction – “saponification”::

The solubility of lipids in nonpolar organic solvents results from their significant hydrocarbon component. The hydrocarbon portion of the compound is responsible for its “oiliness” or “fattiness.” The word lipid comes from the Greek lipos, which means “fat.”

Characterization of fatsCharacterization of fats. The composition, quality and purity of а . The composition, quality and purity of а given oil or fat is determined by means of а number of physical and given oil or fat is determined by means of а number of physical and chemical tests. The usual physical tests include determination of m, chemical tests. The usual physical tests include determination of m, р, specific gravity, viscosity, etc. while the chemical tests include р, specific gravity, viscosity, etc. while the chemical tests include determination of certain values discussed below.determination of certain values discussed below.

• 1. Acid number1. Acid number. It is the number of milligrams of potassium . It is the number of milligrams of potassium hydroxide required to neutralise the free fatty acids in 1g. of the hydroxide required to neutralise the free fatty acids in 1g. of the oil or fat. Thus it indicates the amount of free fatty acids present oil or fat. Thus it indicates the amount of free fatty acids present in oil or fat. А high acid value indicates а stale oil or fat stored in oil or fat. А high acid value indicates а stale oil or fat stored under improper conditions.under improper conditions.

• 2. Saponification number.2. Saponification number. It is number of milligrams of It is number of milligrams of potassium hydroxide required to completely hydrolysis of l g. of potassium hydroxide required to completely hydrolysis of l g. of the oil or fat. Thus it is а measure of fatty acids present as the oil or fat. Thus it is а measure of fatty acids present as esters in а given oil or fat. The saponification value gives an idea esters in а given oil or fat. The saponification value gives an idea about the molecular weight of fat or oil. The saponification about the molecular weight of fat or oil. The saponification number and molecular weight of an oil are inversely proportional number and molecular weight of an oil are inversely proportional to each other; thus high saponification number indicates that the to each other; thus high saponification number indicates that the fat is made up of low molecular weight fatty acids and vice fat is made up of low molecular weight fatty acids and vice versa. It is also helpful in detecting adulteration of а given fat by versa. It is also helpful in detecting adulteration of а given fat by one of the lower or higher saponfication value.one of the lower or higher saponfication value.

• 3. Iodine number.3. Iodine number. It is the number of grams of iodine that It is the number of grams of iodine that combine with 100 g. of oil or fat. It is а measure of the degree of combine with 100 g. of oil or fat. It is а measure of the degree of unsaturation of а fat or oil; а high iodine number indicates а high unsaturation of а fat or oil; а high iodine number indicates а high degree of unsaturation of the fatty acids of the fat.degree of unsaturation of the fatty acids of the fat.

• Difference between saponification and acid numbers named Difference between saponification and acid numbers named ether number which characterizes contain of the remainders of ether number which characterizes contain of the remainders of fatty acids.fatty acids.

2). Oxidation of fates. 2). Oxidation of fates. Oxidation cases rancidity Oxidation cases rancidity of fates. During oxidation form aldehydes with short of fates. During oxidation form aldehydes with short carbon chain.carbon chain.

Oxidation at the soft conditions (water solution of KMnO4) cases formation of glycols. At the rigid conditions carbon skeleton destroys with formation of remainders of carbonic acids with shorter carbon chains.

Fats, which predominantly contain saturated fatty acids, by oxidation form ketones.

3). 3). HydrogenationHydrogenation.. Some or all of the double bonds of Some or all of the double bonds of

polyunsaturated oils can be reduced by catalytic hydrogenation. Margarine polyunsaturated oils can be reduced by catalytic hydrogenation. Margarine and shortening are prepared by hydrogenating vegetable oils such as soybean and shortening are prepared by hydrogenating vegetable oils such as soybean oil and sunflower oil until they have the desired consistency. This process is oil and sunflower oil until they have the desired consistency. This process is called “hardening of oils.” The hydrogenation reaction must be carefully called “hardening of oils.” The hydrogenation reaction must be carefully controlled, however, because reducing all the carbon–carbon double bonds controlled, however, because reducing all the carbon–carbon double bonds would produce a hard fat with the consistency of beef tallow. would produce a hard fat with the consistency of beef tallow. Quantity of H2 Quantity of H2 in grams, which are necessary for hydration of 10kg of fats in grams, which are necessary for hydration of 10kg of fats ((hydration numberhydration number) characterizes unsaturating of fat.) characterizes unsaturating of fat.

4). Addition of halogens. 4). Addition of halogens.

Iodine number for plants fats – 100-200, for Iodine number for plants fats – 100-200, for animal fats – 25-86, for fish fats – 100-193.animal fats – 25-86, for fish fats – 100-193.

As might be expected from the properties of the fatty acids, As might be expected from the properties of the fatty acids, fats have a predominance of saturated fatty acids, and oils are fats have a predominance of saturated fatty acids, and oils are composed largely of unsaturated acids. Thus, the melting points of composed largely of unsaturated acids. Thus, the melting points of triglycerides reflect their composition, as shown by the following triglycerides reflect their composition, as shown by the following examples. Natural mixed triglycerides have somewhat lower melting examples. Natural mixed triglycerides have somewhat lower melting points, the melting point of lard being near 30 º C, whereas olive oil points, the melting point of lard being near 30 º C, whereas olive oil melts near -6 º C. Since fats are valued over oils by some Northern melts near -6 º C. Since fats are valued over oils by some Northern European and North American populations, vegetable oils are European and North American populations, vegetable oils are extensively converted to solid triglycerides (e.g. Crisco) by partial extensively converted to solid triglycerides (e.g. Crisco) by partial hydrogenation of their unsaturated components. Some of the hydrogenation of their unsaturated components. Some of the remaining double bonds are isomerized (to trans) in this operation. remaining double bonds are isomerized (to trans) in this operation. These saturated and trans-fatty acid glycerides in the diet have been These saturated and trans-fatty acid glycerides in the diet have been linked to long-term health issues such as atherosclerosis.linked to long-term health issues such as atherosclerosis.

8. Phospholipids. Waxes. Triacylglycerols arise, not by acylation of glycerol

itself, but by a sequence of steps in which the first stage is acyl transfer to L-glycerol 3-phosphate (from reduction of dihydroxyacetone 3-phosphate, formed as described in Section 25.21). The product of this stage is called a phosphatidic acid.

Hydrolysis of the phosphate ester function of the phosphatidic acid gives a diacylglycerol, which then reacts with a third acyl coenzyme A molecule to produce a triacylglycerol. Phosphatidic acids not only are intermediates in the biosynthesis of triacylglycerols but also are biosynthetic precursors of other members of a group of compounds called phosphoglycerides or glycerol phosphatides. Phosphorus-containing derivatives of lipids are known as phospholipids, and phosphoglycerides are one type of phospholipid. One important phospholipid is phosphatidylcholine, also called lecithin. Phosphatidylcholine is a mixture of diesters of phosphoric acid.

An animated display of micelle formation is An animated display of micelle formation is presented below. Notice the brownish material in the presented below. Notice the brownish material in the center of the three-dimensional drawing on the left. center of the three-dimensional drawing on the left. This illustrates a second important factor contributing This illustrates a second important factor contributing to the use of these amphiphiles as cleaning agents. to the use of these amphiphiles as cleaning agents. Micelles are able to encapsulate nonpolar substances Micelles are able to encapsulate nonpolar substances such as grease within their hydrophobic center, and such as grease within their hydrophobic center, and thus solubilize it so it is removed with the wash thus solubilize it so it is removed with the wash water. Since the micelles of anionic amphiphiles have water. Since the micelles of anionic amphiphiles have a negatively charged surface, they repel one another a negatively charged surface, they repel one another and the nonpolar dirt is effectively emulsified. To and the nonpolar dirt is effectively emulsified. To summarize, summarize, the presence of a soap or a detergent in the presence of a soap or a detergent in water facilitates the wetting of all parts of the water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble object to be cleaned, and removes water-insoluble dirt by incorporation in micellesdirt by incorporation in micelles. If the animation . If the animation has stopped, it may be restarted by clicking on it.has stopped, it may be restarted by clicking on it.

Classification of Classification of phospholipidsphospholipids

The oldest amphiphilic cleaning agent known to humans The oldest amphiphilic cleaning agent known to humans is soap. Soap is manufactured by the base-catalyzed hydrolysis is soap. Soap is manufactured by the base-catalyzed hydrolysis (saponification) of animal fat (see below). Before sodium (saponification) of animal fat (see below). Before sodium hydroxide was commercially available, a boiling solution of hydroxide was commercially available, a boiling solution of potassium carbonate leached from wood ashes was used. Soft potassium carbonate leached from wood ashes was used. Soft potassium soaps were then converted to the harder sodium soaps potassium soaps were then converted to the harder sodium soaps by washing with salt solution. The importance of soap to human by washing with salt solution. The importance of soap to human civilization is documented by history, but some problems civilization is documented by history, but some problems associated with its use have been recognized. One of these is associated with its use have been recognized. One of these is caused by the weak acidity (pKa ca. 4.9) of the fatty acids. caused by the weak acidity (pKa ca. 4.9) of the fatty acids. Solutions of alkali metal soaps are slightly alkaline (pH 8 to 9) Solutions of alkali metal soaps are slightly alkaline (pH 8 to 9) due to hydrolysis. If the pH of a soap solution is lowered by due to hydrolysis. If the pH of a soap solution is lowered by acidic contaminants, insoluble fatty acids precipitate and form a acidic contaminants, insoluble fatty acids precipitate and form a scum. A second problem is caused by the presence of calcium scum. A second problem is caused by the presence of calcium and magnesium salts in the water supply (hard water). These and magnesium salts in the water supply (hard water). These divalent cations cause aggregation of the micelles, which then divalent cations cause aggregation of the micelles, which then deposit as a dirty scum.deposit as a dirty scum.

Washing action of soapsWashing action of soaps

WaxesWaxes are water-repelling solids that are part of the

protective coatings of a number of living things, including the leaves of plants, the fur of animals, and the feathers of birds. They are usually mixtures of esters in which both the alkyl and acyl group are unbranched and contain a dozen or more carbon atoms. Beeswax, for example, contains the ester triacontyl hexadecanoate as one component of a complex mixture of hydrocarbons, alcohols, and esters.

• Wax is а mixture of esters of high molecular Wax is а mixture of esters of high molecular weight alcohols and high molecular weight fatty weight alcohols and high molecular weight fatty acids.acids.

• Waxes are saроinfied with great difficulty than fats Waxes are saроinfied with great difficulty than fats and are not attacked by lipase. Although waxes and are not attacked by lipase. Although waxes may be saponified by prolonged boiling with may be saponified by prolonged boiling with alcoholic KOH, they are more easily saponified by alcoholic KOH, they are more easily saponified by treating а solution of the wax in petroleum ether treating а solution of the wax in petroleum ether with absolute alcohol and metallic sodium, with with absolute alcohol and metallic sodium, with sodium ethoxide. The saponification products оf sodium ethoxide. The saponification products оf waxes are water-soluble soaps (sodium »Its of waxes are water-soluble soaps (sodium »Its of higher fatty acids); while the water insoluble long-higher fatty acids); while the water insoluble long-chain alcohols appear in the "unsaponifiable chain alcohols appear in the "unsaponifiable matter" fraction. Waxes contain about 31 -55% of matter" fraction. Waxes contain about 31 -55% of the unsaponifiable matter, while fats and oils the unsaponifiable matter, while fats and oils contain only 1 - 2% unsaponifiable matter.contain only 1 - 2% unsaponifiable matter.

• Waxes dividing on animal’s (spermaceti, bees wax, Waxes dividing on animal’s (spermaceti, bees wax, lanoline and others) and plants (carnauba wax).lanoline and others) and plants (carnauba wax).

• Bees wax.Bees wax. It contains esters derived from alcohols having It contains esters derived from alcohols having 24 - 30 carbon atoms, include palmitate of miriсуl alcohol 24 - 30 carbon atoms, include palmitate of miriсуl alcohol (С30H61ОН) and n-hexacosanol (С26Н53ОН).(С30H61ОН) and n-hexacosanol (С26Н53ОН).

• СН3(CН2)14COOC30H61 СН3 СН3(CН2)14COOC30H61 СН3 (CН2)14COOC26H53 (CН2)14COOC26H53

• miricyl patmitate n- hexacosanyl patmitatemiricyl patmitate n- hexacosanyl patmitate• Spermaceti.Spermaceti. It is obtained from the head of the sperm It is obtained from the head of the sperm

whale. It is rich in ester of cetyl alcohol (С16Н33ОН) and whale. It is rich in ester of cetyl alcohol (С16Н33ОН) and palmitinic acid: СН3 (C Н2 ) 14COOC16H33 - cetyl palmitinic acid: СН3 (C Н2 ) 14COOC16H33 - cetyl palmitatepalmitate

• Spermaceti is used in making of candles.Spermaceti is used in making of candles.• Sperm Oil.Sperm Oil. It is а liquid wax and occurs with spermaceti It is а liquid wax and occurs with spermaceti

in the sperm whale. It is а valuable lubricant used for in the sperm whale. It is а valuable lubricant used for delicate instruments, such as watches. It does not become delicate instruments, such as watches. It does not become gummy, as many oils do.gummy, as many oils do.

• Carnauba wax.Carnauba wax. It is found in the leaves of the carnauba It is found in the leaves of the carnauba palm of Brazil. It is used as an ingredient in the palm of Brazil. It is used as an ingredient in the manufacture of various wax polishes. Because waxes are manufacture of various wax polishes. Because waxes are very inert chemically, they make an excellent protective very inert chemically, they make an excellent protective coating.coating.

• Lanolin or wool wax.Lanolin or wool wax. It is obtained from wool and is It is obtained from wool and is used in making ointments and salves. used in making ointments and salves.

9. Nonsaponifiable lipids9. Nonsaponifiable lipids 1). Prostaglandins – physiologically 1). Prostaglandins – physiologically

active substances with biogenic active substances with biogenic origin, stimulate smooth muscles and origin, stimulate smooth muscles and lowers blood pressure. All lowers blood pressure. All prostaglandins contain carboxyl prostaglandins contain carboxyl group and 20 carbon atoms in group and 20 carbon atoms in molecule, they are derivatives of molecule, they are derivatives of eyicosanic acid.eyicosanic acid.

Research in physiology carried out in the 1930s established that the lipid fraction of semen contains small amounts of substances that exert powerful effects on smooth muscle. Sheep prostate glands proved to be a convenient source of this material and yielded a mixture of structurally related substances referred to collectively as prostaglandins. We now know that prostaglandins are present in almost all animal tissues, where they carry out a variety of regulatory functions. Prostaglandins are extremely potent substances and exert their physiological effects at very small concentrations. Because of this, their isolation was difficult, and it was not until 1960 that the first members of this class, designated PGE1 and PGF1, were obtained as pure compounds.

All the prostaglandins are 20-carbon carboxylic acids and contain a cyclopentane ring. All have hydroxyl groups at C-11 and C-15 (for the numbering of the positions in prostaglandins). Prostaglandins belonging to the F series have an additional hydroxyl group at C-9, and a carbonyl function is present at this position in the various PGEs. The subscript numerals in their abbreviated names indicate the number of double bonds. Prostaglandins are believed to arise from unsaturated C20-carboxylic acids such as arachidonic acid. Mammals cannot biosynthesize arachidonic acid directly.

They obtain linoleic acid from vegetable oils in their diet and extend the carbon chain of linoleic acid from 18 to 20 carbons while introducing two more double bonds. Linoleic acid is said to be an essential fatty acid, forming part of the dietary requirement of mammals. Animals fed on diets that are deficient in linoleic acid grow poorly and suffer a number of other disorders, some of which are reversed on feeding them vegetable oils rich in linoleic acid and other polyunsaturated fatty acids. One function of these substances is to provide the raw materials for prostaglandin biosynthesis.

Physiological responses to prostaglandins encompass a variety of effects. Some prostaglandins relax bronchial muscle, others contract it. Some stimulate uterine contractions and have been used to induce therapeutic abortions. PGE1 dilates blood vessels and lowers blood pressure; it inhibits the aggregation of platelets and offers promise as a drug to reduce the formation of blood clots. The long-standing question of the mode of action of aspirin has been addressed in terms of its effects on prostaglandin biosynthesis. Prostaglandin biosynthesis is the body’s response to tissue damage and is manifested by pain and inflammation at the affected site. Aspirin has been shown to inhibit the activity of an enzyme required for prostaglandin formation. Aspirin reduces pain and inflammation—and probably fever as well—by reducing prostaglandin levels in the body.

Much of the fundamental work on prostaglandins and related compounds was carried out by Sune Bergström and Bengt Samuelsson of the Karolinska Institute (Sweden) and by Sir John Vane of the Wellcome Foundation (Great Britain). These three shared the Nobel Prize for physiology or medicine in 1982. Bergström began his research on prostaglandins because he was interested in the oxidation of fatty acids. That research led to the identification of a whole new class of biochemical mediators. Prostaglandin research has now revealed that other derivatives of oxidized polyunsaturated fatty acids, structurally distinct from the prostaglandins, are also physiologically important. These fatty acid derivatives include, for example, a group of substances known as the leukotrienes, which have been implicated as mediators in immunological processes.

Prostaglandins have cyclopentane ring. According to allocation of Prostaglandins have cyclopentane ring. According to allocation of double bonds in fivemember cycle and side chains prostaglandins double bonds in fivemember cycle and side chains prostaglandins marked by litters A, B, C, D, E and F.marked by litters A, B, C, D, E and F.

According to the number of double bonds in side chains every According to the number of double bonds in side chains every group of prostaglandins divided on series that marked as group of prostaglandins divided on series that marked as indexes.indexes.

In the names ofIn the names of prostaglandins orientation of prostaglandins orientation of hydroxyl group in location 9 according to the hydroxyl group in location 9 according to the carbon chain at C8 mark carbon chain at C8 mark αα or or ββ. . αα – means cis- – means cis-configuration, configuration, ββ – trance. – trance.

2). 2). Isoprenoides – products of isoprene Isoprenoides – products of isoprene transformation. Some vitamins and hormones transformation. Some vitamins and hormones have isoprenoides structure.have isoprenoides structure.

Isoprenoides includes terpens, carotinoids and steroidsIsoprenoides includes terpens, carotinoids and steroids

10. Terpenes and terpenoids. 10. Terpenes and terpenoids. Terpene Terpene

biosynthesis.biosynthesis. A terpene is a naturally occurring hydrocarbon A terpene is a naturally occurring hydrocarbon

based on combinations of the isoprene unit. based on combinations of the isoprene unit. Terpenoids are compounds related to terpenes, which Terpenoids are compounds related to terpenes, which may include some oxygencontaining derivatives may include some oxygencontaining derivatives (alcohols, aldehydes and ketones), however the two (alcohols, aldehydes and ketones), however the two terms are often used interchangeably. terms are often used interchangeably.

TerpenesTerpenes are a large and varied class of are a large and varied class of hydrocarbons, produced primarily by a wide variety hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are which emit terpenes from their osmeterium. They are the major components of resin, and of turpentine the major components of resin, and of turpentine produced from resin.produced from resin.

The name "terpene" is derived from the word The name "terpene" is derived from the word "turpentine". In addition to their roles as end-products in many "turpentine". In addition to their roles as end-products in many organisms, terpenes are major biosynthetic building blocks organisms, terpenes are major biosynthetic building blocks within nearly every living creature. Steroids, for example, are within nearly every living creature. Steroids, for example, are derivatives of the triterpene squalene. When terpenes are derivatives of the triterpene squalene. When terpenes are modified chemically, such as by oxidation or rearrangement of modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally the carbon skeleton, the resulting compounds are generally referred to as terpenoids. Some authors will use the term referred to as terpenoids. Some authors will use the term terpene to include all terpenoids. Terpenoids are also known as terpene to include all terpenoids. Terpenoids are also known as isoprenoids. Terpenes and terpenoids are the primary isoprenoids. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and constituents of the essential oils of many types of plants and flowers. Essential oils are used widely as natural flavor flowers. Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery, and in additives for food, as fragrances in perfumery, and in traditional and alternative medicines such as aromatherapy. traditional and alternative medicines such as aromatherapy. Synthetic variations and derivatives of natural terpenes and Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. Vitamin A is an perfumery and flavors used in food additives. Vitamin A is an example of a terpene.example of a terpene.

Terpene biosynthesis.Terpene biosynthesis.The reaction of dimethylallyl The reaction of dimethylallyl

pyrophosphate with isopentenyl pyrophosphate with isopentenyl pyrophosphate forms geranyl pyrophosphate, a pyrophosphate forms geranyl pyrophosphate, a 10-carbon compound. In the first step of the 10-carbon compound. In the first step of the reaction, isopentenyl pyrophosphate acts as a reaction, isopentenyl pyrophosphate acts as a nucleophile and displaces a pyrophosphate nucleophile and displaces a pyrophosphate group from dimethylallyl pyrophosphate. group from dimethylallyl pyrophosphate. Pyrophosphate is an excellent leaving group: Pyrophosphate is an excellent leaving group: Its four OH-groups. Therefore, three of the Its four OH-groups. Therefore, three of the four groups will be primarily in their basic four groups will be primarily in their basic forms at physiological pH A proton is forms at physiological pH A proton is removed in the next step, resulting in the removed in the next step, resulting in the formation of geranyl pyrophosphate.formation of geranyl pyrophosphate.

The following scheme shows how some of the many The following scheme shows how some of the many monoterpenes could be synthesized monoterpenes could be synthesized from geranyl from geranyl pyrophosphate:pyrophosphate:

11. Classification of terpenes.Terpenes may be classified by the number of Terpenes may be classified by the number of

terpene units in the molecule; a prefix in the name terpene units in the molecule; a prefix in the name indicates the number of terpene units needed to indicates the number of terpene units needed to assemble the molecule. A single terpene unit is assemble the molecule. A single terpene unit is formed from two molecules of isoprene, so that a formed from two molecules of isoprene, so that a monomonoterpene consists of one terpene but two isoprene terpene consists of one terpene but two isoprene units.units.

HemiterpenesHemiterpenes consist of consist of a single isoprenea single isoprene unit. unit. Isoprene itself is considered the only hemiterpene, but Isoprene itself is considered the only hemiterpene, but oxygen-containing derivatives such as prenol and oxygen-containing derivatives such as prenol and isovaleric acid are hemiterpenoids.isovaleric acid are hemiterpenoids.

MonoterpenesMonoterpenes consist of consist of two isoprenetwo isoprene units and units and have the molecular formula C10H16. Examples of have the molecular formula C10H16. Examples of monoterpenes are: geraniol, limonene and terpineol.monoterpenes are: geraniol, limonene and terpineol.

SesquiterpenesSesquiterpenes consist of consist of three isoprenethree isoprene units and have units and have the molecular formula Cthe molecular formula C1515HH2424. Examples of . Examples of sesquiterpenes are: farnesenes, farnesol. The sesquiterpenes are: farnesenes, farnesol. The sesqui-sesqui- prefix means one and a half.prefix means one and a half.

DiterpenesDiterpenes are composed for are composed for four isoprenefour isoprene units and units and have the molecular formula Chave the molecular formula C2020HH3232. They derive from . They derive from geranylgeranyl pyrophosphate. Examples of diterpenes geranylgeranyl pyrophosphate. Examples of diterpenes are cafestol, kahweol, cembrene and taxadiene are cafestol, kahweol, cembrene and taxadiene (precursor of taxol). Diterpenes also form the basis for (precursor of taxol). Diterpenes also form the basis for biologically important compounds such as retinol, biologically important compounds such as retinol, retinal, and phytol. They are known to be antimicrobial retinal, and phytol. They are known to be antimicrobial and antiinflammatory.and antiinflammatory.

SesterterpenesSesterterpenes, terpenes having 25 carbons and , terpenes having 25 carbons and five five isopreneisoprene units, are rare relative to the other sizes. The units, are rare relative to the other sizes. The sester-sester- prefix means half to three, i.e. two and a half. prefix means half to three, i.e. two and a half. Examples of sesterterpenes are geranylfarnesol.Examples of sesterterpenes are geranylfarnesol.

TriterpenesTriterpenes consist of consist of six isoprenesix isoprene units and have the units and have the molecular formula Cmolecular formula C3030HH4848. The linear triterpene . The linear triterpene squalene, the major constituent of shark liver oil, is squalene, the major constituent of shark liver oil, is derived from the reductive coupling of two molecules of derived from the reductive coupling of two molecules of farnesyl pyrophosphate. Squalene is then processed farnesyl pyrophosphate. Squalene is then processed biosynthetically to generate either lanosterol or biosynthetically to generate either lanosterol or cycloartenol, the structural precursors to all the steroids.cycloartenol, the structural precursors to all the steroids.

TetraterpenesTetraterpenes contain contain eight isopreneeight isoprene units and have the units and have the molecular formula Cmolecular formula C4040HH6464. Biologically important . Biologically important tetraterpenes include the acyclic lycopene, the tetraterpenes include the acyclic lycopene, the monocyclic gamma-carotene, and the bicyclic monocyclic gamma-carotene, and the bicyclic αα- and - and ββ--carotenes.carotenes.

PolyterpenesPolyterpenes consist of long chains of consist of long chains of many isoprenemany isoprene units. Natural rubber consists of polyisoprene in which units. Natural rubber consists of polyisoprene in which the double bonds are cis. Some plants produce a the double bonds are cis. Some plants produce a polyisoprene with trans double bonds, known as gutta-polyisoprene with trans double bonds, known as gutta-perchapercha

Classification of terpenes

The higher terpenes are formed not by successive addition of C5 units but by the coupling of simpler terpenes. Thus, the triterpenes (C30) are derived from two molecules of farnesyl pyrophosphate, and the tetraterpenes (C40) from two molecules of geranyl pyrophosphate. These carbon–carbon bond-forming processes involve tail-to-tail couplings and proceed by a more complicated mechanism than that just described. The enzyme-catalyzed reactions that lead to geraniol and farnesol (as their pyrophosphate esters) are mechanistically related to the acid-catalyzed dimerization of alkenes. The reaction of an allylic pyrophosphate or a carbocation with a source of electrons is a recurring theme in terpene biosynthesis and is invoked to explain the origin of more complicated structural types. Consider, for example, the formation of cyclic monoterpenes. Neryl pyrophosphate, formed by an enzyme-catalyzed isomerization of the E double bond in geranyl pyrophosphate, has the proper geometry to form a six-membered ring via intramolecular attack of the double bond on the allylic pyrophosphate unit.

Loss of a proton from the tertiary carbocation formed in this step gives limonene, an abundant natural product found in many citrus fruits. Capture of the carbocation by water gives -terpineol, also a known natural product.

MonoterpensMonoterpensThey are the terpenes that have been known for several They are the terpenes that have been known for several

centuries as components of the fragrant oils obtained from centuries as components of the fragrant oils obtained from leaves, flowers and fruits. Monoterpenes, with sesquiterpenes, leaves, flowers and fruits. Monoterpenes, with sesquiterpenes, are the main constituents of essential oils.are the main constituents of essential oils.

Acyclic monoterpens:Acyclic monoterpens:They can be considered as derivatives of 2,6-dimethyloctane. They can be considered as derivatives of 2,6-dimethyloctane.

In the basis of carbon skeleton In the basis of carbon skeleton acyclic acyclic monoterpens are structures of isoprene monoterpens are structures of isoprene isomeric dimers: myrcene and ocimene.isomeric dimers: myrcene and ocimene.

Geraniol and nerol alcohols are derivatives of carbohydrates monoterpens. Geraniol has cis-form and nerol – trance-form.

Among natural molecules, the followings are well Among natural molecules, the followings are well known and have several structural isomers.known and have several structural isomers.

Geraniol and citral present in ether oils, especially in citric oil. They are pheromones.

Monocyclic monoterpenesMonocyclic monoterpenes They are derived from cyclohexane with an isopropyl They are derived from cyclohexane with an isopropyl

substituent. substituent. The mostThe most important members are limonene important members are limonene and methane.and methane.

Limonene (dipentene) can be obtained by isoprene isomerisation with heating to 150 C in soldered ampoule. At 500-700 C reverse processes takes place.

– – Catalytically hydrogenisation of limoneneCatalytically hydrogenisation of limonene

– – hydratation of limonene:hydratation of limonene:

Menthane (1-isopropilmethylbenzol) is obtained from p-cimol (n-isopropilmethylbenzol) hydration.

From hydroxyderivatives of menthane most important is From hydroxyderivatives of menthane most important is menthol (menthanol-3), which has tree asymmetric menthol (menthanol-3), which has tree asymmetric centers. (-)Menthol synthesized by reducing of centers. (-)Menthol synthesized by reducing of menthon.menthon.

(+)Menthol in industry synthesized by alkylation of m-crezol with following (+)Menthol in industry synthesized by alkylation of m-crezol with following hydration of tymol.hydration of tymol.

Menthol has antiseptic, sedative, analgesic properties (Boromenthol, Pectussine)

Terpinehydrate (monohydrate Terpinehydrate (monohydrate menthandiol-1,8) use in medicine in menthandiol-1,8) use in medicine in treatment of chronic bronchitis. treatment of chronic bronchitis.

Bicyclic monoterpenes:Bicyclic monoterpenes:The same tertiary carbocation serves as the precursor to

numerous bicyclic monoterpenes. A carbocation having a bicyclic skeleton is formed by intramolecular attack of the electrons of the double bond on the positively charged carbon. In the basis of bicyclic monoterpenes are four cyclic terpenic carbohydrates:

αα-Pinene contains in turpentine oil – -Pinene contains in turpentine oil – turpentine (up to 75 %). turpentine (up to 75 %).

Heating with dilute acids (H2SO4, HNO3):Heating with dilute acids (H2SO4, HNO3):

After oxidation on air forms verbenon:

Borneol – alcohol of bornane (camphane) chain: Isoborneol is borneol’s diastereomer:

Synthesis of difficult esters of borneolSynthesis of difficult esters of borneol

Oxidation by chromic acid:

Interaction between borneol and acids:

Camphene can hydrolyze in acidic medium with Camphene can hydrolyze in acidic medium with formation of isoborneol.formation of isoborneol.

Camphor – bicyclic ketone, has two asymmetric atoms, but dosen’t have diastereomers.

Camphor uses for stimulation of respiratory and vesselmoving centers, has antiseptic properties, stimulates metabolite processes.

Tishchenko synthesisTishchenko synthesis

Methylene group in α-location (according to carbonyl group) has CH-acidic properties.

Oxidation of camphor with nitrate acid

12. Carotenoids.Carotenoids are natural pigments characterized

by a tail-to-tail linkage between two C20 units and an extended conjugated system of double bonds. They are the most widely distributed of the substances that give color to our world and occur in flowers, fruits, plants, insects, and animals. It has been estimated that biosynthesis from acetate produces approximately a hundred million tons of carotenoids per year. The most familiar carotenoids are lycopene and -carotene, pigments found in numerous plants and easily isolable from ripe tomatoes and carrots, respectively.

Carotene – yellow-red pigment, contains Carotene – yellow-red pigment, contains in carrot, milk and butter. Carotene is a in carrot, milk and butter. Carotene is a mixture of tree isomers – mixture of tree isomers – αα-, -, ββ- and - and γγ--carotene.carotene.

Carotenoids absorb visible light and dissipate its energy as heat, thereby protecting the organism from any potentially harmful effects associated with sunlight-induced photochemistry. They are also indirectly involved in the chemistry of vision, owing to the fact that -carotene is the biosynthetic precursor of vitamin A, also known as retinol, a key substance in the visual process.

13. 13. Steroids.Hormones are chemical messengers—organic compounds

synthesized in glands and delivered by the bloodstream to target tissues in order to stimulate or inhibit some process. Many hormones are steroids. Because steroids are nonpolar compounds, they are lipids. Their nonpolar character allows them to cross cell membranes, so they can leave the cells in which they are synthesized and enter their target cells. All steroids contain a tetracyclic ring system. The four rings are designated A, B, C, and D. A, B, and C are six-membered rings and D is a five-membered ring. The carbons in the steroid ring system are numbered as shown. We have seen that rings can be trans fused or cis fused and that trans fused rings are more stable. In steroids, the B, C, and D rings are all trans fused. In most naturally occurring steroids, the A and B rings are also trans fused.

Classification of steroids.Some of the common categories of steroids:Some of the common categories of steroids:Animal steroids Animal steroids

– Insect steroids Insect steroids • Ecdysteroids such as ecdysteroneEcdysteroids such as ecdysterone

– Vertebrate steroids Vertebrate steroids • Steroid hormones Steroid hormones

– Sexual steroids are a subset of sex hormones that produce sex differences or Sexual steroids are a subset of sex hormones that produce sex differences or support reproduction. They include androgens, estrogens, and progestagens.support reproduction. They include androgens, estrogens, and progestagens.

– Corticosteroids include glucocorticoids and mineralocorticoids. Corticosteroids include glucocorticoids and mineralocorticoids. Glucocorticoids regulate many aspects of metabolism and immune function, Glucocorticoids regulate many aspects of metabolism and immune function, whereas mineralocorticoids help maintain blood volume and control renal whereas mineralocorticoids help maintain blood volume and control renal excretion of electrolytes. Most medical 'steroid' drugs are corticosteroids.excretion of electrolytes. Most medical 'steroid' drugs are corticosteroids.

– Anabolic steroids are a class of steroids that interact with androgen receptors Anabolic steroids are a class of steroids that interact with androgen receptors to increase muscle and bone synthesis. There are natural and synthetic to increase muscle and bone synthesis. There are natural and synthetic anabolic steroids. In popular language, the word "steroids" usually refers to anabolic steroids. In popular language, the word "steroids" usually refers to anabolic steroids.anabolic steroids.

• Cholesterol, which modulates the fluidity of cell membranes and is the principal Cholesterol, which modulates the fluidity of cell membranes and is the principal constituent of the plaques implicated in atherosclerosis.constituent of the plaques implicated in atherosclerosis.

Plant steroids Plant steroids – PhytosterolsPhytosterols– BrassinosteroidsBrassinosteroids

Fungus steroids Fungus steroids – ErgosterolsErgosterols

Many steroids have methyl groups at the 10- and 13-positions. These are called angular methyl groups. When steroids are drawn, both angular methyl groups are shown to be above the plane of the steroid ring system. Substituents on the same side of the steroid ring (above the ring) system as the angular methyl groups are designated β-substituents (indicated by a solid wedge). Those on the opposite side of the plane of the ring system (below the ring) are α-substituents (indicated by a hatched wedge).

Steroids contain sterines, bile acids, steroid hormones, aglycones of heart glycosides, aglycones of steroid saponines.

SterinesSterines (sterols) – steroid alcohols, which contain in basis structure cholestane. Sterines are 3-hydroxyderivatives of cholestane, may have one or few double bonds. Divided on animal sterines (zoosterines), plant sterines (phytosterines) and sterines of mushrooms (mycosterines).

The most abundant member of the steroid family in animals is cholesterol (cholesterine, cholestene-5-ol-3β) , the precursor of all other steroids. Cholesterol is biosynthesized from squalene, a triterpene. Cholesterol is an important component of cell membranes .Its ring structure makes it more rigid than other membrane lipids. Because cholesterol has eight asymmetric carbons, 256 stereoisomers are possible, but only one exists in nature.

The steroid hormones can be divided into five classes: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestins. Glucocorticoids and mineralocorticoids are synthesized in the adrenal cortex and are collectively known as adrenal cortical steroids. All adrenal cortical steroids have an oxygen at C-11.

• In lipids of human skin cholesteol transforms in vitamin D3 In lipids of human skin cholesteol transforms in vitamin D3 (cholecalciferrol) at the presents of UF-light. (cholecalciferrol) at the presents of UF-light.

ErgosterineErgosterine (ergosterol, 24-methylcholestanetrien-5,7,22-ol- (ergosterol, 24-methylcholestanetrien-5,7,22-ol-33ββ) refers to mycosterine group.) refers to mycosterine group. At the presents of UF-light At the presents of UF-light ergosterol isomerizes in vitamin Dergosterol isomerizes in vitamin D2 2 (ergocalciferrol)(ergocalciferrol)

Bile acidsBile acids produce by liver from cholesterine and are

hydroxyderivatives of cholanic acid.

In human bile present 4 bile

acids, more popular are cholic

and dezoxycholic acids.

In addition to being the precursor of all the steroid hormones in animals, cholesterol is the precursor of the bile acids. In fact, the word cholesterol is derived from the Greek words chole meaning “bile” and stereos meaning “solid.” The bile acids—cholic acid and dezoxycholic acid—are synthesized in the liver, stored in the gallbladder,and secreted into the small intestine, where they act as emulsifying agents so that fats and oils can be digested by water-soluble digestive enzymes. Cholesterol is also the precursor of vitamin D.

• Bile acids exist in organism in connection with glycine Bile acids exist in organism in connection with glycine aminoacid NH2CH2COOH or taurine NH2CH2CH2SO3H.aminoacid NH2CH2COOH or taurine NH2CH2CH2SO3H.

Steroid hormones Steroid hormones • Steroid hormones include Steroid hormones include corticosteroids

and sexual hormones. Corticosteroids produce in the bark of adrenal glands, they are derivatives of pregnane and divided into glucocorticoids and mineralocorticoids.

Glucocorticoids, as their name suggests, are involved in glucose metabolism, as well as in the metabolism of proteins and fatty acids. Cortisone is an example of a glucocorticoid. Because of its anti-inflammatory effect, it is used clinically to treat arthritis and other inflammatory conditions. Most important glucocorticoids are hydrocortisone and cortisone:

•Mineralocorticoids cause increased reabsorption of HCO3

•control the balance of Na+, К+, Cl- ions in cells and balance of water in the kidneys, take part in regulation of blood pressure.. Aldosterone is an example of a mineralocorticoid.

• Most important mineralcorticoids are aldosterone and dezoxycorticosterone:

• In medicine also use synthetic In medicine also use synthetic analogs of hydrocortisone and analogs of hydrocortisone and cortisone – prednisolone, prednisone, cortisone – prednisolone, prednisone, dexamethasone, triamcinolone. dexamethasone, triamcinolone. These substances are more active These substances are more active then natural cthen natural corticoorticosteroids.steroids.

The sexual hormones can be classified into three major groups:

• 1. Estrogens — the female sexual hormones

• 2. Androgens — the male sexual hormones

• 3. Progestins (gestagenes) — the pregnancy hormones

• The male sexual hormones, known as androgens are secreted by the testes, estrogens – female sexual hormones are secreted by the follicles in ovaries, pregnancy hormones form in yellow body of ovaries.

They are responsible for the development of male secondary sexual characteristics during puberty. They also promote

muscle growth. Testosterone and androsterone are androgens. Synthetic steroid with androgen properties – methyltestosterone. Synthetic steroid with androgen properties – methyltestosterone.

• Estrogens Estrogens are synthesized in the ovaries and are synthesized in the ovaries and adrenal cortex and are responsible for the adrenal cortex and are responsible for the development of female secondary sex characteristics development of female secondary sex characteristics at the onset of puberty and for regulation of the at the onset of puberty and for regulation of the menstrual cycle. They also stimulate the menstrual cycle. They also stimulate the development of the mammary glands during development of the mammary glands during pregnancy and induce estrus (heat) in animals.pregnancy and induce estrus (heat) in animals.

• AndrogensAndrogens are synthesized in the testes and are synthesized in the testes and adrenal cortex and promote the development of adrenal cortex and promote the development of secondary male characteristics. They also promote secondary male characteristics. They also promote muscle growth.muscle growth.

• Progestins Progestins are synthesized in the ovaries and the are synthesized in the ovaries and the placenta and prepare the lining of the uterus for placenta and prepare the lining of the uterus for implantation of the fertilized ovum. They also implantation of the fertilized ovum. They also suppress ovulation.suppress ovulation.

Estradiol and estrone (folliculine) are female sexual hormones known as estrogens. They are secreted by the ovaries and are responsible for the development of female secondary sex characteristics. They also regulate the menstrual cycle. Progesterone is the hormone that prepares the lining of the uterus for implantation of an ovum and is essential for the maintenance of pregnancy. It also prevents ovulation during pregnancy.

Although the various steroid hormones have remarkably different physiological effects, their structures are quite similar. For example, the only difference between testosterone and progesterone is the substituent at C-17, and the only difference between androsterone and estradiol is one carbon and six hydrogens, but these compounds make the difference between being male and being female. These examples illustrate the extreme specificity of biochemical reactions.

Synthetic unsteroid estrogens widely use in Synthetic unsteroid estrogens widely use in pharmacy then steroid estrogens:pharmacy then steroid estrogens:

Progestins (gestagenes) — the pregnancy hormones, hormones of yellow body. Maine hestagene hormone is progesterone.

Aglycones of heart glycosides• Heart glycosides in big doses very poisoned substances, in small – has

cardiotonic action. Heart glycosides according to its chemical structure are O-glycosides, in which aglycone has steroid origin, carbohydrate fragment represent by remainders of mono-, di-, tri- or tetrasaccharides.

• According to the character of lactone cycle heart glycosides divided on two groups:

1). Cardenolids – contain at C17 fivemember unsaturated lactone cycle;

2). Buphadienolids – contain at C17 sixmember unsaturated lactone cycle;

Carbohydrate fragment can be represent by D-glucose, D-fructose, D-xylose, D-ramnose and also by methylpentoses:

Heart glycosides of cardenolid group very often contain as aglycones next compounds:

Example of such hExample of such heart glycosides is eart glycosides is

purpureaglycoside Apurpureaglycoside A

Aglycones of steroid saponinesSaponines – group of plant glycosides with Saponines – group of plant glycosides with

high surface activity, cases hemolysis of high surface activity, cases hemolysis of erythrocytes. erythrocytes. According to its chemical According to its chemical structure they are O-glycosides, in which structure they are O-glycosides, in which aglycone has steroid or triterpenoid origin. aglycone has steroid or triterpenoid origin. Most aglycones of steroid saponines Most aglycones of steroid saponines contain spiroketal fragment.contain spiroketal fragment.

14. Properties of cholesterol.14. Properties of cholesterol. Biosynthesis of Biosynthesis of ccholesterolholesterol..Cholesterol and heart disease.

Cholesterol is probably the best-known lipid because of the correlation between cholesterol levels in the blood and heart disease. Cholesterol is synthesized in the liver and is also found in almost all body tissues. Cholesterol is also found in many foods, but we do not require it in our diet because the body can synthesize all we need. A diet high in cholesterol can lead to high levels of cholesterol in the bloodstream, and the excess can accumulate on the walls of arteries, restricting the flow of blood. This disease of the circulatory system is known as atherosclerosis and is a primary cause of heart disease. Cholesterol travels through the bloodstream packaged in particles that also contain cholesterol esters, phospholipids, and proteins.

The particles are classified according to their density. LDL (lowdensity lipoprotein) particles transport cholesterol from the liver to other tissues. Receptors on the surfaces of cells bind LDL particles,allowing them to be brought into the cell so that it can use the cholesterol. HDL (high-density lipoprotein) is a cholesterol scavenger, removing cholesterol from the surfaces of membranes and delivering it back to the liver, where it is converted into bile acids. LDL is the so-called bad cholesterol, whereas HDL is the “good” cholesterol. The more cholesterol we eat, the less the body synthesizes. But this does not mean that the presence of dietary cholesterol has no effect on the total amount of cholesterol in the bloodstream, because dietary cholesterol also inhibits the synthesis of the LDL receptors. So the more cholesterol we eat, the less the body synthesizes, but also, the less the body can get rid of by bringing it into target cells.

Statins are the newest class of cholesterol-reducing drugs. Statins reduce serum cholesterol levels by inhibiting the enzyme that catalyzes the reduction of hydroxymethylglutaryl- CoA to mevalonic acid. Decreasing the mevalonic acid concentration decreases the isopentenyl pyrophosphate concentration, so the biosynthesis of all terpenes, including cholesterol, is diminished. As a consequence of diminished cholesterol synthesis in the liver, the liver expresses more LDL receptors—the receptors that help clear LDL from the bloodstream.

Studies show that for every 10% that cholesterol is reduced, deaths from coronary heart disease are reduced by 15% and total death risk is reduced by 11%. Compactin and lovastatin are natural statins used clinically under the trade names Zocor® and Mevacor® . Atorvastatin (Lipitor)®, a synthetic statin, is now the most popular statin. Lipitor® has greater potency and a longer half-life than natural statins have, because its metabolites are as active as the parent drug in reducing cholesterol levels. Therefore, smaller doses of the drug may be administered. The required dose is reduced further because is marketed as a single enantiomer. In addition, it is more lipophilic than compactin and lovastatin, so it has a greater tendency to remain in the endoplasmic reticulum of the liver cells, where it is needed.

Biosynthesis of Biosynthesis of ccholesterolholesterol..How is cholesterol, the precursor of all the

steroid hormones, biosynthesized? The starting material for the biosynthesis is the triterpene squalene, which must first be converted to lanosterol. Lanosterol is converted to cholesterol in a series of 19 steps. The first step in the conversion of squalene to lanosterol is epoxidation of the 2,3-double bond of squalene. Acid-catalyzed opening of the epoxide initiates a series of cyclizations resulting in the protosterol cation. Elimination of a C-9 proton from the cation initiates a series of 1,2-hydride and 1,2-methyl shifts, resulting in lanosterol.

Synthetic SteroidsSynthetic Steroids The potent physiological effects of steroids led

scientists, in their search for new drugs, to synthesize steroids that are not available in nature and to investigate their physiological effects. Stanozolol and Dianabol are drugs developed in this way. They have the same muscle-building effect as testosterone. Steroids that aid in the development of muscle are called anabolic steroids. These drugs are available by prescription and are used to treat people suffering from traumas accompanied by muscle deterioration. The same drugs have been administered to athletes and racehorses to increase their muscle mass. Stanozolol was the drug detected in several athletes in the 1988 Olympics. Anabolic steroids, when taken in relatively high dosages, have been found to cause liver tumors, personality disorders, and testicular atrophy.

Many synthetic steroids have been found to be much more potent than natural steroids. Norethindrone, for example, is better than progesterone in arresting ovulation. Another synthetic steroid, RU 486, when taken along with prostaglandins, terminates pregnancy within the first nine weeks of gestation. Notice that these oral contraceptives have structures similar to that of rogesterone.

15. Vitamins.15. Vitamins.A A vitamin vitamin is a substance the body cannot is a substance the body cannot

synthesize that is needed in small amounts for normal synthesize that is needed in small amounts for normal body function. Sir Frederick Hopkins was the first to body function. Sir Frederick Hopkins was the first to suggest that diseases such as rickets and scurvy might suggest that diseases such as rickets and scurvy might result from the absence of substances in the diet that result from the absence of substances in the diet that are needed only in very small quantities. Because the are needed only in very small quantities. Because the first such compound recognized to be essential in the first such compound recognized to be essential in the diet was an amine, Casimir Funk incorrectly diet was an amine, Casimir Funk incorrectly concluded that all such compounds were amines and concluded that all such compounds were amines and called them vitamines (“life-amines”). The called them vitamines (“life-amines”). The e e was later was later dropped from the name.dropped from the name.

The essential dietary substances called The essential dietary substances called vitaminsvitamins are are commonly classified as "water soluble" or "fat soluble". Water commonly classified as "water soluble" or "fat soluble". Water soluble vitamins, such as vitamin C, are rapidly eliminated from the soluble vitamins, such as vitamin C, are rapidly eliminated from the body and their dietary levels need to be relatively high. The body and their dietary levels need to be relatively high. The recommended daily allotment (RDA) of vitamin C is 100 mg, and recommended daily allotment (RDA) of vitamin C is 100 mg, and amounts as large as 2 to 3 g are taken by many people without amounts as large as 2 to 3 g are taken by many people without adverse effects. The lipid soluble vitamins, shown in the diagram adverse effects. The lipid soluble vitamins, shown in the diagram below, are not as easily eliminated and may accumulate to toxic below, are not as easily eliminated and may accumulate to toxic levels if consumed in large quantity. The RDA for these vitamins levels if consumed in large quantity. The RDA for these vitamins are:are:Vitamin A   800 Vitamin A   800 μμg ( upper limit ca. 3000 g ( upper limit ca. 3000 μμg)g)Vitamin D   5 to 10 Vitamin D   5 to 10 μμg ( upper limit ca. 2000 g ( upper limit ca. 2000 μμg)g)Vitamin E   15 mg ( upper limit ca. 1 g)Vitamin E   15 mg ( upper limit ca. 1 g)Vitamin K   110 Vitamin K   110 μμg ( upper limit not specified)g ( upper limit not specified)From this data it is clear that vitamins A and D, while essential to From this data it is clear that vitamins A and D, while essential to good health in proper amounts, can be very toxic. Vitamin D, for good health in proper amounts, can be very toxic. Vitamin D, for example, is used as a rat poison, and in equal weight is more than example, is used as a rat poison, and in equal weight is more than 100 times as poisonous as sodium cyanide.100 times as poisonous as sodium cyanide.

16. Water-soluble vitamins.16. Water-soluble vitamins.

Thiamine

Thiamine is a colorless compound with a chemical formula C12H17N4OS. Its structure contains a pyrimidine ring and a thiazole ring linked by a methylene bridge. Thiamine is soluble in water, methanol, and glycerol and practically insoluble in acetone, ether, chloroform, and benzene. It is stable at acidic pH, but is unstable in alkaline solutions. Thiamine is unstable to heat, but stable during frozen storage. It is unstable when exposed to ultraviolet light and gamma irradiation. Thiamine reacts strongly in Maillard-type reactions.

ThiamineThiamine, sometimes called aneurin, is a water-soluble , sometimes called aneurin, is a water-soluble vitamin of the B complex (vitamin Bvitamin of the B complex (vitamin B11), whose phosphate derivatives ), whose phosphate derivatives are involved in many cellular processes. The best characterized form are involved in many cellular processes. The best characterized form is thiamine diphosphate (ThDP), a coenzyme in the catabolism of is thiamine diphosphate (ThDP), a coenzyme in the catabolism of sugars and amino acids. In yeast, ThDP is also required in the first sugars and amino acids. In yeast, ThDP is also required in the first step of alcoholic fermentation.step of alcoholic fermentation.

Thiamine is synthesized in bacteria, fungi and plants. Thiamine is synthesized in bacteria, fungi and plants. Animals must cover all their needs from their food and insufficient Animals must cover all their needs from their food and insufficient intake results in a disease called beriberi affecting the peripheral intake results in a disease called beriberi affecting the peripheral nervous system (polyneuritis) and/or the cardiovascular system, with nervous system (polyneuritis) and/or the cardiovascular system, with fatal outcome if not cured by thiamine administration. In less severe fatal outcome if not cured by thiamine administration. In less severe deficiency, nonspecific signs include malaise, weight loss, deficiency, nonspecific signs include malaise, weight loss, irritability and confusion. Today, there is still a lot of work devoted irritability and confusion. Today, there is still a lot of work devoted to elucidating the exact mechanisms by which thiamine deficiency to elucidating the exact mechanisms by which thiamine deficiency leads to the specific symptoms observed (see below). Finally, new leads to the specific symptoms observed (see below). Finally, new thiamine phosphate derivatives have recently been discovered, thiamine phosphate derivatives have recently been discovered, emphasizing the complexity of thiamine metabolism and the need emphasizing the complexity of thiamine metabolism and the need for more research in the field.for more research in the field.

Pyridoxine

Pyridoxine is one of the compounds that can be called vitamin B6, along with pyridoxal and pyridoxamine. It differs from pyridoxamine by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride. Pyridoxine assists in the balancing of sodium and potassium as well as promoting red blood cell production. It is linked to cardiovascular health by decreasing the formation of homocysteine. It has been suggested that Pyridoxine might help children with learning difficulties, and may also prevent dandruff, eczema, and psoriasis. In addition, pyridoxine can help balance hormonal changes in women and aid in immune system.

Lack of pyridoxine may cause anemia, nerve Lack of pyridoxine may cause anemia, nerve damage, seizures, skin problems, and sores in the mouth. It damage, seizures, skin problems, and sores in the mouth. It is required for the production of the monoamine is required for the production of the monoamine neurotransmitters serotonin, dopamine, norepinephrine and neurotransmitters serotonin, dopamine, norepinephrine and epinephrine, as it is the precursor to pyridoxal phosphate: epinephrine, as it is the precursor to pyridoxal phosphate: cofactor for the enzyme aromatic amino acid cofactor for the enzyme aromatic amino acid decarboxylase. This enzyme is responsible for converting decarboxylase. This enzyme is responsible for converting the precursors 5-hydroxytryptophan (5-HTP) into serotonin the precursors 5-hydroxytryptophan (5-HTP) into serotonin and levodopa (L-DOPA) into dopamine, noradrenaline and and levodopa (L-DOPA) into dopamine, noradrenaline and adrenaline. As such it has been implicated in the treatment adrenaline. As such it has been implicated in the treatment of depression and anxiety. A very good source of of depression and anxiety. A very good source of pyridoxine is dragon fruit from South East pyridoxine is dragon fruit from South East Asia .Pyridoxine is not normally found in plants and plants Asia .Pyridoxine is not normally found in plants and plants are not the principal source of this vitamin. This vitamin is are not the principal source of this vitamin. This vitamin is made by certain bacteria. Some vegetarians may get made by certain bacteria. Some vegetarians may get adequate pyridoxine simply from eating plants that have adequate pyridoxine simply from eating plants that have traces of soil (like potato skins). Most people get their traces of soil (like potato skins). Most people get their supply of this vitamin from either milk or meat products.supply of this vitamin from either milk or meat products.

Niacin

Niacin, also known as vitamin B3 or nicotinic acid, is a water-soluble vitamin that prevents the deficiency disease pellagra. It is an organic compound with the molecular formula C6H5NO2. It is a derivative of pyridine, with a carboxyl group (COOH) at the 3-position. Other forms of vitamin B3 include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH2), as well as more complex amides and a variety of esters. The terms niacin, nicotinamide, and vitamin B3 are often used interchangeably to refer to any one of this family of molecules, since they have a common biochemical activity.

Niacin is converted to nicotinamide and then to Niacin is converted to nicotinamide and then to NAD and NADP NAD and NADP in vivoin vivo. Although the two are identical in . Although the two are identical in their vitamin activity, nicotinamide does not have the same their vitamin activity, nicotinamide does not have the same pharmacological effects as niacin, which occur as side-pharmacological effects as niacin, which occur as side-effects of niacin's conversion. Thus nicotinamide does not effects of niacin's conversion. Thus nicotinamide does not reduce cholesterol or cause flushing, although reduce cholesterol or cause flushing, although nicotinamide may be toxic to the liver at doses exceeding 3 nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults. Niacin is a precursor to NADH, NAD, g/day for adults. Niacin is a precursor to NADH, NAD, NAD+, NADP and NADPH, which play essential NAD+, NADP and NADPH, which play essential metabolic roles in living cells. Niacin is involved in both metabolic roles in living cells. Niacin is involved in both DNA repair, and the production of steroid hormones in the DNA repair, and the production of steroid hormones in the adrenal gland. Niacin is one of five vitamins associated adrenal gland. Niacin is one of five vitamins associated with a pandemic deficiency disease: these are niacin with a pandemic deficiency disease: these are niacin (pellagra), vitamin C (scurvy), thiamine (beriberi), vitamin (pellagra), vitamin C (scurvy), thiamine (beriberi), vitamin D (rickets), and vitamin A (vitamin A deficiency, which D (rickets), and vitamin A (vitamin A deficiency, which has no common name but is one of the most common has no common name but is one of the most common symptomatic deficiencies worldwide)symptomatic deficiencies worldwide)

Biotin

Biotin, also known as vitamin H or B7, has the chemical formula C10H16N2O3S (Biotin; Coenzyme R, Biopeiderm), is a water-soluble B-complex vitamin which is composed of an ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is a cofactor in the metabolism of fatty acids and leucine, and in gluconeogenesis.

Biotin is widely distributed in a variety of foods, Biotin is widely distributed in a variety of foods, but most often at low concentrations. Estimates are that but most often at low concentrations. Estimates are that the typical U.S. diet provides roughly 40 ug/day. There the typical U.S. diet provides roughly 40 ug/day. There are only a couple of foods which contain biotin in large are only a couple of foods which contain biotin in large amounts, including royal jelly and brewer's yeast The amounts, including royal jelly and brewer's yeast The best natural sources of biotin in human nutrition are best natural sources of biotin in human nutrition are liver, legume, soybeans, swiss chard, tomatoes, liver, legume, soybeans, swiss chard, tomatoes, romaine lettuce, and carrots. This includes almonds, romaine lettuce, and carrots. This includes almonds, eggs, onions, cabbage, cucumber, cauliflower, goat's eggs, onions, cabbage, cucumber, cauliflower, goat's milk, cow's milk, raspberries, strawberries, halibut, milk, cow's milk, raspberries, strawberries, halibut, oats, and walnuts. The most important natural sources oats, and walnuts. The most important natural sources in feeding nonruminant animals are oilseed meals, in feeding nonruminant animals are oilseed meals, alfalfa, and dried yeasts. It is important to note that the alfalfa, and dried yeasts. It is important to note that the biotin content of food varies and can be influenced by biotin content of food varies and can be influenced by factors such as plant variety, season, and yield factors such as plant variety, season, and yield (endosperm-to-pericarp ratio).(endosperm-to-pericarp ratio).

Riboflavin

Riboflavin (E101), also known as vitamin B2, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a wide variety of cellular processes. Like the other B vitamins, it plays a key role in energy metabolism, and is required for the metabolism of fats, ketone bodies, carbohydrates, and proteins. Milk, cheese, leafy green vegetables, liver, kidneys, legumes such as mature soybeans, yeast, and almonds are good sources of vitamin B2, but exposure to light destroys riboflavin. The name "riboflavin" comes from "ribose" and "flavin".

Vitamin BVitamin B1212 is a water soluble vitamin with a key role in the is a water soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is normally involved in the of blood. It is one of the eight B vitamins. It is normally involved in the metabolism of every cell of the body, especially affecting DNA synthesis metabolism of every cell of the body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production. and regulation, but also fatty acid synthesis and energy production. Vitamin BVitamin B1212 is the name for a class of chemically-related compounds, all of is the name for a class of chemically-related compounds, all of which have vitamin activity. It is structurally the most complicated which have vitamin activity. It is structurally the most complicated vitamin. Biosynthesis of the basic structure of the vitamin can only be vitamin. Biosynthesis of the basic structure of the vitamin can only be accomplished by bacteria, but conversion between different forms of the accomplished by bacteria, but conversion between different forms of the vitamin can be accomplished in the human body. A common synthetic vitamin can be accomplished in the human body. A common synthetic form of the vitamin, cyanocobalamin, does not occur in nature, but is used form of the vitamin, cyanocobalamin, does not occur in nature, but is used in many pharmaceuticals, supplements and as food additive, due to its in many pharmaceuticals, supplements and as food additive, due to its stability and lower cost. stability and lower cost.

In the body it is converted to the physiological forms, methylcobalamin In the body it is converted to the physiological forms, methylcobalamin and adenosylcobalamin, leaving behind the cyanide, albeit in minimal and adenosylcobalamin, leaving behind the cyanide, albeit in minimal concentration. More recently, hydroxocobalamin, methylcobalamin and, concentration. More recently, hydroxocobalamin, methylcobalamin and, adenosylcobalamin can also be found in more expensive pharmacological products adenosylcobalamin can also be found in more expensive pharmacological products and food supplements. The utility of these is presently debated.and food supplements. The utility of these is presently debated.

Historically, vitamin BHistorically, vitamin B1212 was discovered from its relationship to the was discovered from its relationship to the disease pernicious anemia, which is an autoimmune disease that destroys parietal disease pernicious anemia, which is an autoimmune disease that destroys parietal cells in the stomach that secrete intrinsic factor. Intrinsic factor is crucial for the cells in the stomach that secrete intrinsic factor. Intrinsic factor is crucial for the normal absorption of Bnormal absorption of B1212, therefore, a lack of intrinsic factor, as seen in pernicious , therefore, a lack of intrinsic factor, as seen in pernicious anemia, causes a vitamin Banemia, causes a vitamin B1212 deficiency. Many other subtler kinds of vitamin B deficiency. Many other subtler kinds of vitamin B12 12 deficiency, and their biochemical effects, have since been elucidated. Vitamin Bdeficiency, and their biochemical effects, have since been elucidated. Vitamin B1212 is normally involved in the metabolism of every cell of the body, especially is normally involved in the metabolism of every cell of the body, especially affecting the DNA synthesis and regulation but also fatty acid synthesis and energy affecting the DNA synthesis and regulation but also fatty acid synthesis and energy production. However, many (though not all) of the effects of functions of Bproduction. However, many (though not all) of the effects of functions of B1212 can can be replaced by sufficient quantities of folic acid (another B vitamin), since Bbe replaced by sufficient quantities of folic acid (another B vitamin), since B1212 is is used to regenerate folate in the body. Most "Bused to regenerate folate in the body. Most "B12 12 deficient symptoms" are actually deficient symptoms" are actually folate deficient symptoms, since they include all the effects of pernicious anemia folate deficient symptoms, since they include all the effects of pernicious anemia and megaloblastosis, which are due to poor synthesis of DNA when the body does and megaloblastosis, which are due to poor synthesis of DNA when the body does not have a proper supply of folic acid for the production of thymine.not have a proper supply of folic acid for the production of thymine.

The "antiscorbutic" factor of fresh fruits, which prevents the development of the typical symptoms of scurvy in humans, is a carbohydrate derivative known as vitamin C or ascorbic acid. This substance is not a carboxylic acid, but a lactone, and owes its acidic properties (and ease of oxidation) to the presence of an enediol grouping. It belongs to the L series by the glyceraldehydeconvention.Most animals are able to synthesize vitamin C in their livers but, in the course of evolution, man has lost this capacity.

17.Water insoluble (lipid-soluble) vitamines.17.Water insoluble (lipid-soluble) vitamines.

Vitamin KVitamin K (K from "Koagulations-Vitamin" in (K from "Koagulations-Vitamin" in German and Scandinavian languages) denotes a group of German and Scandinavian languages) denotes a group of lipophilic, hydrophobic vitamins that are needed for the lipophilic, hydrophobic vitamins that are needed for the posttranslational modification of certain proteins, mostly posttranslational modification of certain proteins, mostly required for blood coagulation. Chemically they are 2-required for blood coagulation. Chemically they are 2-methyl-1,4-naphthoquinone derivatives. Vitamin K1 is also methyl-1,4-naphthoquinone derivatives. Vitamin K1 is also known as phylloquinone or phytomenadione. Vitamin K2 known as phylloquinone or phytomenadione. Vitamin K2 (menaquinone, menatetrenone) is normally produced by (menaquinone, menatetrenone) is normally produced by bacteria in the intestines, and dietary deficiency is bacteria in the intestines, and dietary deficiency is extremely rare unless the intestines are heavily damaged, extremely rare unless the intestines are heavily damaged, are unable to absorb the molecule, or due to decreased are unable to absorb the molecule, or due to decreased production by normal flora, as seen in broad spectrum production by normal flora, as seen in broad spectrum antibiotic acid. There are three synthetic forms of vitamin antibiotic acid. There are three synthetic forms of vitamin K, vitamins K3, K4 and K5 which are used in many areas K, vitamins K3, K4 and K5 which are used in many areas including the pet food industry (vitamin K3) and to inhibit including the pet food industry (vitamin K3) and to inhibit fungal growth (vitamin K5) fungal growth (vitamin K5)

RetinolRetinol, the animal form of vitamin A, is a fat-soluble , the animal form of vitamin A, is a fat-soluble vitamin important in vision and bone growth. It is also a vitamin important in vision and bone growth. It is also a diterpenoid. Retinol is among the most useable forms of vitamin diterpenoid. Retinol is among the most useable forms of vitamin A, which also include Retinal (aldehyde form), Retinoic acid A, which also include Retinal (aldehyde form), Retinoic acid (acid form) and retinyl ester (ester form). These chemical (acid form) and retinyl ester (ester form). These chemical compounds are collectively known as Retinoids, and all possess compounds are collectively known as Retinoids, and all possess the biological activity of all-trans retinol as a common feature in the biological activity of all-trans retinol as a common feature in their structure. Structurally, retinoids possess a their structure. Structurally, retinoids possess a ββ-ionone ring and -ionone ring and a polyunsaturated side chain, with either an alcohol, aldehyde, a a polyunsaturated side chain, with either an alcohol, aldehyde, a carboxylic acid group or an ester group. The side chain is carboxylic acid group or an ester group. The side chain is composed of four isoprenoid units, with a series of conjugated composed of four isoprenoid units, with a series of conjugated double bonds which may exist in trans or cis configuration.double bonds which may exist in trans or cis configuration.

Retinol is ingested in a precursor form; animal sources Retinol is ingested in a precursor form; animal sources (liver and eggs) contain retinyl esters, whereas plants (carrots, (liver and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol, while pro-vitamin A carotenoids can be esters results in retinol, while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. The best described irreversibly oxidized to produce retinoic acid. The best described active retinoid metabolites are 11-active retinoid metabolites are 11-ciscis-retinal and the all-trans and -retinal and the all-trans and 9-cis-isomers of retinoic acid.9-cis-isomers of retinoic acid.

Vitamin DVitamin D is a group of fat-soluble prohormones, the two major is a group of fat-soluble prohormones, the two major forms of which are vitamin D2 (or ergocalciferol) and vitamin D3 (or forms of which are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). The term vitamin D also refers to metabolites and other cholecalciferol). The term vitamin D also refers to metabolites and other analogues of these substances. Vitamin D3 is produced in skin exposed to analogues of these substances. Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B radiationsunlight, specifically ultraviolet B radiation..

Vitamin D deficiency can result from Vitamin D deficiency can result from inadequate intake coupled with inadequate sunlight inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, exposure, disorders that limit its absorption, conditions that impair conversion of vitamin D into conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders, active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders. or, rarely, by a number of hereditary disorders. Deficiency results in impaired bone mineralization, Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly children and osteomalacia in adults, and possibly contributes to osteoporosis. However, sunlight contributes to osteoporosis. However, sunlight exposure, to avoid deficiency, carries other risks, exposure, to avoid deficiency, carries other risks, including skin cancer; this risk is avoided with including skin cancer; this risk is avoided with dietary absorption, either through diet or as a dietary dietary absorption, either through diet or as a dietary supplement.supplement.

Vitamin D plays an important role in the maintenance of Vitamin D plays an important role in the maintenance of organ systems:organ systems:

Vitamin D regulates the calcium and phosphorus Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption levels in the blood by promoting their absorption from food in the intestines, and by promoting re-from food in the intestines, and by promoting re-absorption of calcium in the kidneys, which absorption of calcium in the kidneys, which enables normal mineralization of bone and enables normal mineralization of bone and prevents hypocalcemic tetany. It is also needed prevents hypocalcemic tetany. It is also needed for bone growth and bone remodeling by for bone growth and bone remodeling by osteoblasts and osteoclasts..osteoblasts and osteoclasts..

In the absence of vitamin K or with drugs In the absence of vitamin K or with drugs (particularly blood thinners) that interfere with (particularly blood thinners) that interfere with Vitamin K metabolism, Vitamin D can promote Vitamin K metabolism, Vitamin D can promote soft tissue calcification.soft tissue calcification.

It inhibits parathyroid hormone secretion from the It inhibits parathyroid hormone secretion from the parathyroid gland.parathyroid gland.

Vitamin D affects the immune system by Vitamin D affects the immune system by promoting phagocytosis, anti-tumor activity, and promoting phagocytosis, anti-tumor activity, and immunomodulatory functions. immunomodulatory functions.

• TocopherolTocopherol (or (or TCPTCP), a class of chemical compounds of ), a class of chemical compounds of which many have vitamin E activity, describes a series of which many have vitamin E activity, describes a series of organic compounds consisting of various methylated organic compounds consisting of various methylated phenols. Because the vitamin activity was first identified in phenols. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, it was given the 1936 from a dietary fertility factor in rats, it was given the name "tocopherol" from the Greek words “name "tocopherol" from the Greek words “τοκοςτοκος” [birth], ” [birth], and “and “φορεινφορειν”, [to bear or carry] meaning in sum "to carry a ”, [to bear or carry] meaning in sum "to carry a pregnancy," with the ending "-ol" signifying its status as a pregnancy," with the ending "-ol" signifying its status as a chemical alcohol.chemical alcohol.

• Tocotrienols, which are related compounds, may also have Tocotrienols, which are related compounds, may also have vitamin E activity. All of these various derivatives with vitamin E activity. All of these various derivatives with vitamin activity may correctly be referred to as "vitamin E." vitamin activity may correctly be referred to as "vitamin E." Tocopherols and tocotrienols are fat-soluble antioxidants Tocopherols and tocotrienols are fat-soluble antioxidants but also seem to have many other functions in the body. The but also seem to have many other functions in the body. The compound compound αα-tocopherol-tocopherol, a common form of tocopherol , a common form of tocopherol added to food products, is denoted by the E number added to food products, is denoted by the E number E307E307..

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