Parvin Pasalar

Arsia Jamali

Tehran University of Medical Sciences

Why Why CarbohydratesCarbohydrates? ?

SugarsSugars Objectives: After studying this session you Objectives: After studying this session you

have to: have to: Define what a carbohydrate molecule is Define what a carbohydrate molecule is Recognise and classify carbohydrate Recognise and classify carbohydrate

moleculesmolecules Explain why carbohydrates are importantExplain why carbohydrates are important Explain different types of isomerism in Explain different types of isomerism in

monosaccharidesmonosaccharides Name other molecules that interact with Name other molecules that interact with

carbohydrates and explain how and why these carbohydrates and explain how and why these interactions occurinteractions occur

Know different names, roles, definitions, Know different names, roles, definitions, structurs and classifications of sugars, MS, structurs and classifications of sugars, MS, OS(DS) & PSOS(DS) & PS

Sugars/ ImportanceSugars/ Importance 11 . .PhotosynthesisPhotosynthesis energy stored in energy stored in

carbohydratescarbohydrates 22 . .The The most abundantmost abundant organic organic

molecules in naturemolecules in nature 33 . .Metabolic precursorsMetabolic precursors of all of all

other biomoleculesother biomolecules 44 . .Central in the metabolismCentral in the metabolism of of

plants and animalsplants and animals 55 . .Important Important structuralstructural component component

of plants (cellulose, pectate), of plants (cellulose, pectate), animals (hyaloronic acid, chitin) animals (hyaloronic acid, chitin) and bacterial cells (murein)and bacterial cells (murein)

Sugars/ ImportanceSugars/ Importance 6. 6. FuelFuel; In animals, they represent a ; In animals, they represent a

major part of the caloric intake.major part of the caloric intake. 7. 7. Energy StorageEnergy Storage ( glycogen, starch, ( glycogen, starch,

inulin).inulin). 8. 8. Cell-cell recognitionCell-cell recognition 9. 9. AdhesionAdhesion (hyaluronic acid) (hyaluronic acid) 10. They are important in 10. They are important in immune immune

responsesresponses either as antigenic either as antigenic determinants or antibody structuredeterminants or antibody structure

11. 11. Protein ageingProtein ageing ( non-enzymatic ( non-enzymatic glycation)glycation)

12. 12. Age determinantAge determinant in some protein in some protein and cells (Asialo glycoprotein)and cells (Asialo glycoprotein)

Sugars/ ImportanceSugars/ Importance

Sugars/ Different names and Sugars/ Different names and definitiondefinition

1- Carbohydrates { Cn(H1- Carbohydrates { Cn(H22O)n }O)n }: : Substances with equal ratio of Substances with equal ratio of carbon atom and water.carbon atom and water.

Exceptions: Exceptions:

*Sugars that have not the formula *Sugars that have not the formula (deoxyribose & Fucose) (deoxyribose & Fucose)

*Substances that are not sugars *Substances that are not sugars but have the formula { but have the formula { formaldehyde formaldehyde (C H(C H22O) & O) & lactic acidlactic acid {C3(H {C3(H22O)3}O)3}

Sugars/ Different names and Sugars/ Different names and definitiondefinition

2- Glucides2- Glucides ( glycos= Gk. sweet) OR ( glycos= Gk. sweet) OR

SaccharidesSaccharides ( sakcharon= Gk. sugar) ( sakcharon= Gk. sugar)

Exceptions:Exceptions:

*Sugars that are not sweet (*Sugars that are not sweet (cellulose cellulose & starch& starch))

*Sweet substances that are not sugars *Sweet substances that are not sugars ((glycerol, monilin, aspartam and glycerol, monilin, aspartam and saccharine)saccharine)

3- Ose3- Ose ( suffix from Fr. sugar) ( suffix from Fr. sugar) 4- Definition:4- Definition: Polyhydroxy compound Polyhydroxy compound

with an aldehyde or a ketone group or with an aldehyde or a ketone group or those compounds that by hydrolysis those compounds that by hydrolysis produce such compounds.produce such compounds.

SugarsSugars Different classifications:Different classifications: 1- With respect to the 1- With respect to the numbernumber of building of building

blocks they are classified into three groups: blocks they are classified into three groups: a-Monosaccharidea-Monosaccharide (mono= (mono= oneone) or ) or

simple sugar have just one unit.simple sugar have just one unit. b-Oligosaccharideb-Oligosaccharide (oligo= (oligo= fewfew) that ) that

are composed of 2-10 Monosaccharide are composed of 2-10 Monosaccharide unitsunits

c-Polysaccharidesc-Polysaccharides (poly = (poly = manymany) are ) are much larger sugars , containing hundreds much larger sugars , containing hundreds of monosaccharide unitsof monosaccharide units

2- With respect being 2- With respect being purepure sugar or having sugar or having other components are classified into:other components are classified into:

a- Glycoproteina- Glycoprotein & & Proteoglycane Proteoglycane bb-- glycolipid and lipopolysccharide glycolipid and lipopolysccharide..

Sugars/General ideaSugars/General idea The The simplestsimplest sugar is sugar is

Glyceraldehyde.Glyceraldehyde. All other simple sugars are All other simple sugars are

derivedderived from Glyceraldehyde. from Glyceraldehyde. The structure of The structure of GlyceraldehydeGlyceraldehyde is is

the basis of sugar classification the basis of sugar classification into two different into two different D or LD or L classes. classes.

They have They have asymmetric (chiral)asymmetric (chiral) carbon. carbon.

The only sugar that has not any The only sugar that has not any

assymetricassymetric carbon is carbon is dihydroxyacetone.dihydroxyacetone. Glucose ( dextrose) is the Glucose ( dextrose) is the reference reference

sugarsugar in medical sciences and is the in medical sciences and is the most most abundantabundant sugar that is present sugar that is present and used as the and used as the fuelfuel in all living in all living organisms.organisms.

Sugars/General ideaSugars/General idea

MS/ Different MS/ Different definitionsdefinitions

They are called simple sugar, because by hydrolysis they can not make any other simpler sugars.

They are called Polyhydroxyaldehyde or Polyhydroxyketone.

In other words:They are Polyhydroxy compound with

an aldehyde or a ketone group.

MonosaccharidesMonosaccharides Different Classifications and Different Classifications and

nomenclatures:nomenclatures:

1- On the basis of the 1- On the basis of the numbers of carbon numbers of carbon atomsatoms: Triose, tetrose, pentose, hexose and : Triose, tetrose, pentose, hexose and heptose.heptose.

2- On the basis of the 2- On the basis of the functional groupfunctional group: : Aldose and ketose.Aldose and ketose. In most cases the name of In most cases the name of a ketose is make by addition of “a ketose is make by addition of “ulul” between ” between the name of sugar and ose. the name of sugar and ose. ExampleExample: Ribose : Ribose and riband ribululose, heptose and heptose, heptose and heptululose.ose.

3-On the basis of 3-On the basis of both above propertiesboth above properties: : Aldotriose, ketotriose.Aldotriose, ketotriose.

MonosaccharidesMonosaccharides Different properties and rolesDifferent properties and roles :: 1- 1- They are composed of 3-7 (3-8) They are composed of 3-7 (3-8)

carbon atomscarbon atoms

2-All are 2-All are solublesoluble, , reducingreducing and easily and easily can make can make crystalcrystal..

3- 3- D- familyD- family sugars are the most sugars are the most abundantabundant sugars in the living sugars in the living organism.organism.

44--Because of the functional groups (Because of the functional groups (aldoaldo, , ketoketo and and hydroxylhydroxyl groups they are groups they are reactivereactive compoundscompounds

6- By becoming cyclic, 5-7 carbon 6- By becoming cyclic, 5-7 carbon sugars are called sugars are called internalinternal hemiacetal hemiacetal oror hemiketal. hemiketal. In other In other words they are produced by joining words they are produced by joining of the functional group with a of the functional group with a hydroxyl group of same molecule.hydroxyl group of same molecule.

7- By combination they make 7- By combination they make oligooligo and and polysaccharidespolysaccharides..

8-There are different 8-There are different isomerismsisomerisms for for the MSthe MS

MS/ MS/ Different properties Different properties and rolesand roles

MS/ Asymmetric (chiral) MS/ Asymmetric (chiral) carboncarbon

Chiral means Chiral means like hands.like hands.It is referred to a carbon atom It is referred to a carbon atom with with 4 different groups linked 4 different groups linked to it.to it.

Two different 1- methyl glucoside of Glc !

Sugars/ General structure/ Cyclization

Sugars/ Cyclic (Ring) structure

A: Haworth projection

Monosaccharides Different isomerisms:Different isomerisms:

* Functional* Functional

* Ring* Ring

* Optic* Optic

MS/ isomerisms/MS/ isomerisms/1- 1- FunctionalFunctional

* *AldoseAldose is referred to is referred to those simple sugars those simple sugars that have an that have an aldehyde groupaldehyde group as as their functional their functional groupgroup..

* *KetoseKetose is referred is referred to those simple to those simple sugars that have an sugars that have an ketoneketone group as group as their functional their functional groupgroup..

Aldose to ketose conversion by enediol Aldose to ketose conversion by enediol intermediateintermediate

MS/ isomerisms/Functional

MS/ isomerisms/ 2- Ring

* * By the linking of By the linking of functional group to functional group to a hydroxyla hydroxyl groupgroup, 4-7 carbon sugars , 4-7 carbon sugars make a furan or pyran like rings.make a furan or pyran like rings. In In this way, the carbon ofthis way, the carbon of functional functional group is called group is called anomeric carbon. anomeric carbon.

PyranosePyranose is a six member ring is a six member ring sugar that may be in chair sugar that may be in chair or boat conformation.or boat conformation. FuranoseFuranose is a five member ring is a five member ring sugar that its conformationsugar that its conformation is like a letter envelope.is like a letter envelope. Note that: Note that: Linear and cyclic sugars Linear and cyclic sugars

are isomers.are isomers.

MS/ Isomerisms

Furanose/ Pyranose Chair/ Boat

Ring Conformational

MS/ isomerisms/3- Optic or Steroisomerism

It is because of the presence of It is because of the presence of asymmetric carbon atom and is asymmetric carbon atom and is classified into four types:classified into four types:

* D & L* D & L

* Enantiomerism* Enantiomerism

* Epimerism* Epimerism

* Anomerism* Anomerism

MS/ isomerisms/Streoisomerism(Optic

)

a- Enantiomerism

b- Epimerism

c- Anomerism

* D & L do not refer to the rotation of polarized light, but are stand for the family of the sugar. For showing the rotation of polarized light (+) or (- )sign are used.

* D- family sugars are abundant, natural sugars that are derived from D- glyceraldehyde so the OH group of the last asymmetric atom is at right.

* L- family sugars are rear sugars and just found in the oligosaccharides present as antigenic moieties. They can not be metabolized and make energy. The OH group of the last asymmetric atom is at left..

MS/ isomerisms/3- Optic/ 1- D & L1- D & L

* Definition: * All OH groups have

opposite orientation* A pair of enantiomers have

same name, but are shown with D or L letters .

* They rotate polarized light equally into two opposite directions, if one is D(-) the other one will be L(+).

Example: D(+) Glc & L(-) Glc or D(+)Fru & L(-) Fru

MS/ isomerisms/3- Optic/ 2- Enantiomerism ( mirror image)

Definition: The difference Definition: The difference between the between the OH OH orientationorientation of just of just oneone asymmetric carbon atom asymmetric carbon atom other than the last oneother than the last one (the one that determines (the one that determines the family of a sugar).the family of a sugar).

Example: Example: Mannose ( epimer 2 Mannose ( epimer 2

Glc)Glc) Allose ( epimer 3 Allose ( epimer 3

Glc)Glc) Galactose ( epimer 4 Galactose ( epimer 4

Glc)Glc)

MS/ isomerisms/3- Optic/ 3- 3- EpimerismEpimerism

Definition:Definition: * * OH orientationOH orientation of of

anomeric carbonanomeric carbon is is the basis of this the basis of this classification. classification.

ββ anomer : Same anomer : Same orientation with the orientation with the side chainside chain

( the last carbon atom)( the last carbon atom) αα anomer : opposit anomer : opposit

orientation with the orientation with the side chainside chain

Example: Example: αα or or ββ anomer of D(+)Glc.anomer of D(+)Glc.

MS/ isomerisms/3- Optic/ 4- 4- AnomerismAnomerism

MS/ isomerisms/ optic / MS/ isomerisms/ optic / MutarotaionMutarotaion

Mutarotaion: Mutarotaion: αα or or ββ anomer can convert to anomer can convert to each other via an open chain intermediate. In each other via an open chain intermediate. In doing so the degree of polarized light rotation doing so the degree of polarized light rotation changes. changes.

At equilibrium 1/3 will be At equilibrium 1/3 will be αα and 2/3 will beand 2/3 will be ββ anomer.anomer.

MS/ Chiral carbon & optic MS/ Chiral carbon & optic isomer numberisomer number

For For each chiraleach chiral center there are center there are two two optic isomers.optic isomers.

They are They are not superimposable.not superimposable. The number of chiral carbon in:The number of chiral carbon in: Linear aldoses: n= N-2 so linear Linear aldoses: n= N-2 so linear

Glc has 2Glc has 244 optic isomers optic isomers Cyclic aldoses: n=N-1 so cyclic Cyclic aldoses: n=N-1 so cyclic

Glc has 2Glc has 255 optic isomers optic isomers Linear ketoses: n= N-3 so linear Linear ketoses: n= N-3 so linear

Fru has 2Fru has 233 optic isomers optic isomers Cyclic ketoses: n= N-2 so cyclic Cyclic ketoses: n= N-2 so cyclic

Fru has 2Fru has 24 4 optic isomers optic isomers

Isomers

Enantiomers

are mirror image

Configurational

Ketose

Steroisomers Same atom

connectivity different arrangement in pace

Functional Isomers different atom

connectivity

Aldose

Conformational

Diasteromers are not mirror image

(epimers)

Boat Chair

Anomers

OPTIC Ring

Furan Pyran

Envelop

MS/MS/Different reactionsDifferent reactions::

*Oxidation*Oxidation

*Reduction*Reduction

*Ester formation*Ester formation

*Amination*Amination

*Glycoside formation*Glycoside formation

MS/ Reactions/Oxidation1: Aldonic acid: Oxidation of aldehyde

Group.Example: Gluconic acid. 2: Uronic acid: Oxidation of

primary alcohol group.

Example: glucoronic acid.

3: Aldaric acid: Oxidation of aldehyde

and primary alcohol group

Example: Glucaric acid ( saccharic acid),

Mannaric acid ( arabic gum)

Galactaric acid (mucic acid)

MS/ Reactions/Oxidation

4: Furfural formation

Oxidation and dehydration of M.S by very strong acids

Example: Furfural from pentoses and hydroxymethyl furfural from hexoses

MS/ Reactions/ Reduction1-Polyalcohols * Reduction by gaining hydrogen

Example: Sorbitol from glucose, fructose and mannose

2- Deoxysugars *Reduction by losing oxygen =

deoxysugar formation

Example: Deoxyribose form ribose, Fucose from L-galactose

Examples of Polyalcohols

Examples of Deoxysugars

MS/ Reactions/ Amination

Amino sugars: Glucosamine, mannosamine

N- acetyl amino sugars : N- acetyl glucosamine, N- acetyl mannosamine

Sialic acids: NAM+ PA

Glc A Man A Gal A NAG

MS/ Reactions/ Ester formation

• * Phosphate esters: have an important role in metabolism.

Example: G6P, G1, 6 bis P, R5P.

*Sulfate esters: of sugars are found in the glycosaminoglycanes (GAG).

Example: Gal 6 sulfate, Gal 4 sulfate.

MS/ Reactions/ Glycoside formation

* O- glycoside compounds: acetal or ketal are formed by combination of an alcohol ( a sugar or hydroxylic amino acids) with anomeric carbon of a sugar.

Example: oligo or polysaccharides.* N- glycoside compounds: they are formed by

combination of nitrogen containing bases or amidic amino acids with anomeric carbon of a sugar.

Example: nucleosides.

MS/ Reactions/ Glycoside formation

O- glycoside N- glycoside

Monosaccharide Monosaccharide DerivativesDerivatives

Reducing sugars: sugars with Reducing sugars: sugars with free anomeric carbonsfree anomeric carbons - they will - they will reduce oxidizing agents, such as reduce oxidizing agents, such as peroxide, ferricyanide and some peroxide, ferricyanide and some metals (Cu and Ag) metals (Cu and Ag)

These redox reactions convert These redox reactions convert the sugar to a sugar acid the sugar to a sugar acid

Glucose is a reducing sugar - so Glucose is a reducing sugar - so these reactions are the basis for these reactions are the basis for diagnostic tests for blood sugardiagnostic tests for blood sugar

OligosaccharidesOligosaccharides DefinitionDefinition::

*They are composed of 2-10 sugars.*They are composed of 2-10 sugars.

*Disaccharides are most important *Disaccharides are most important oligosaccharides that are found in free oligosaccharides that are found in free form.form.

ExampleExample: Maltose, sucrose.: Maltose, sucrose.

*Oligosaccharides with more than 2 *Oligosaccharides with more than 2 residues usually are found as residues usually are found as bound to the other compounds.bound to the other compounds.

ExampleExample: glycoproteins or : glycoproteins or glycolipidsglycolipids..

DS/ Reactions/ Glycoside DS/ Reactions/ Glycoside formationformation

DS formed by linkage of DS formed by linkage of simple MSsimple MS

α (D) glucopyranosyl 1, 2 fructofuranoside

β (D) galactopyranosyl 1 4 glucopyranose

DS/ Classification and DS/ Classification and nomenclaturenomenclature

1- 1- ReducingReducing disaccharides are formed by disaccharides are formed by combination of anomeric carbon of one combination of anomeric carbon of one sugar with a hydroxyl group of another sugar with a hydroxyl group of another one. Because of one free anomeric carbon one. Because of one free anomeric carbon they are reducing. An yle suffix is added to they are reducing. An yle suffix is added to the name of non-reducing residue. the name of non-reducing residue.

ExampleExample: Maltose, lactose.: Maltose, lactose. 2-2-Non-reducingNon-reducing disaccharides are formed disaccharides are formed

by combination of anomeric carbons of by combination of anomeric carbons of two sugars. Because there is no free two sugars. Because there is no free anomeric carbon they are non-reducing. anomeric carbon they are non-reducing. An yle suffix is added to the name of one An yle suffix is added to the name of one and an ide suffix is added to the other one.and an ide suffix is added to the other one.

ExampleExample: Sucrose, Trehalose: Sucrose, Trehalose..