Dr. Siham Gritly 1

Principle of Biochemistry4-Lipids

Course code: HFB324Credit hours: 3 hours

Dr. Siham Gritly

Dr. Siham Gritly 2

Fatty acids

Dr. Siham Gritly 3

Terms to be learned

• Triacylglycerol three fatty acids esterified to glycerol• cis-C=C double bond; the hydrogens on each of the

two carbon atoms are on the same side of the C=C plane (as opposed to trans-C=C bonds in which the hydrogen atoms are on opposite sides)

• essential fatty acids; polyunsaturated fatty acids; synthesized by plants but not by mammals

• fatty acid; unbranched hydrocarbon chain with a carboxylic acid functional group at one end and acyl group at the other end (CH3)

• Lipoprotein; protein with covalently attached lipids

Dr. Siham Gritly 4

• Bilayers; two lipid layers stacked so that the hydrocarbon chains face each other, and the head groups face out and interact with water

• Liposome lipid bilayers forming small vesicles in aqueous solution

• Micelle aggregation of lipids in aqueous solution• phospholipids (or glycerophospholipids) major components of

cell membrane; two fatty acids and phosphoric acid esterified to glycerol (CH2OH—CHOH—CH2OH)

• polyunsaturated (fatty acid) fatty acid containing more than one C=C double bond

Dr. Siham Gritly 5

• saturated (fatty acid); fatty acid containing no double bonds

• Amphipathic; a molecule that has a polar region at one end location and a nonpolar region at another

• Sphingolipids; complex lipids with sphingosine, a C18 amino alcohol, as backbone; found predominantly in nerve and brain tissue

Dr. Siham Gritly 6

Lipidsfats, oils, steriod and waxes

• Lipids are long hydrocarbon molecules • Lipids are chemical compound naturally occurring

substance; consist of carbon, hydrogen, and oxygen, • widely found in plant and animal kingdoms.• A molecule of dietary fat consists of several fatty

acids (containing long chains of carbon and hydrogen atoms), bonded to a glycerol. They are typically found as triglycerides (three fatty acids attached to one glycerol backbone).

Dr. Siham Gritly 7

Classification of fats according to National Academy of Sciences

• Total fat, provide 20-35 % of total energy intake• Saturated fatty acids, risk of (Coronary Heart Disease

CHD) milk fat, coconut• Cis monounsaturated fatty acids, (olive oil) prevent

(CHD), peanut oil• Cis polyunsaturated fatty acids of two type health

benefit; fish oil, sunflower oil, corn oil, fish oil• 1-Omega 6 fatty acids• 2-Omega 3 fatty acids• Trans fatty acids, risk of (CHD), margin, shortening

Dr. Siham Gritly 8

Common properties of lipids

• Insoluble in water; Most lipids are strictly nonpolar and hydrophobic, so they dissolve in nonpolar substances, such as ether, chloroform and benzene.

• Lipids are heterogeneous group of compounds related more by their physical rather than by chemical properties

• Lipids contain large regions of just carbon and hydrogen, as carbon-carbon bonds and carbon-hydrogen bonds

Dr. Siham Gritly 9

• Stored in adipose tissues (triacylglycerols)• Related health problems such as obesity,

atherosclerosis • the proportion of oxygen is low, so lipids are mostly

hydrocarbons• The chemical structure of fats and oils, the most

common lipids, is based on fatty acid building blocks and an alcohol, glycerol

• Fats are "hard" or solid at room temperature• Oils are liquids at room temperature

Dr. Siham Gritly 10

major functions of lipids in human body;

• They serve as structural components of biological membranes, cellular constituents (lipoproteins)

• *main source of energy, provide the body with 2/3 of energy (9 kal) They provide energy reserves, in the form of triacylglycerols

• *main source of fat soluble vitamins A, K, E D• *protection against traumatic injury an shock• *maintain body temperature• Electrical insulator

Dr. Siham Gritly 11

Classification of lipids • Simple lipids;-ester of fatty acid and alcohols• 1-fats; ester of fatty acids with glycerol• 2-waxes; ester of fatty acids with monohyri

alcohol• Complex lipids;- ester of fatty acid containing

additional to alcohol and fatty acids other groups• 1-phospholipids; containing phosphoric acid and

nitrogen containing bases such as glycerophospholipid and sphingphospholipids

Dr. Siham Gritly 12

• 2-glycolipids; containing fatty acid, sphingosine and carbohydrates

• 3-other complex lipid; lipoproteins

• Derived lipids;- include glycerol, steroid, alcohol in addition to glycerol and sterols

Dr. Siham Gritly 13

Fatty Acids (FA)

• Fatty acids are long-chain hydrocarbon molecules containing a carboxylic acid

• The numbering of carbons in fatty acids begins with the carbon of the carboxylate group.

Dr. Siham Gritly 14

Fatty acids structure

• Fatty acids consists of a carboxyl group attached to a long hydrocarbon chain and methyl group (CH3) at the other end CH3(CH2)nCOOH

Dr. Siham Gritly 15

• Essential fatty acids and nonessential• essential fatty acids; that they must be provided in the diet.• plants are capable of synthesizing linoleic and α-linolenic

acid, humans can acquire these fats by consuming a variety of plants or else by eating the meat of animals that have consumed these plant fats.

• These two essential fatty acids are also referred to as omega fatty acids. The use of the Greek omega, ω, refers to the end of the fatty acid opposite to that of the –COOH group.

• Linoleic acid is an omega-6 PUFA and α-linolenic is an omega-3 PUFA

Dr. Siham Gritly 16

The carbon chains of fatty acids can vary in 3 ways

• 1-The number of carbons in the chain or the Length of chain in fatty acid

• 4 – 22 carbons long• Short chains are more soluble• Short chains are more easily broken down• Short chains oxidize more easily

Dr. Siham Gritly 17

• 2-Degree of saturation. The extent to which the chain is saturated with hydrogen

• Saturated• Monounsaturated• Polyunsaturated• Most plant fats are unsaturated, • Fish oils are unsaturated• Other animal fats tend to be saturated

Dr. Siham Gritly 18

• 3-The shape of the chain (straight or bent)• The shape of carbon chain varies with

saturation• Saturated and trans fatty acids have straight

carbon chain

Dr. Siham Gritly 19

Nomenclature of fatty acids

• 1-Fats may be classified as saturated or unsaturated depending on the structure of the fatty acids involved.

• 2-delta ∆ and omega ω systems

• 3-cis and trans geometric isomerisms

Dr. Siham Gritly 20

Saturated and unsaturated fatty acids

• Saturated acids end in; anoic• Unsaturated fatty acid end in; enoic• Saturated fatty acids; containing no double bond. Based on

acetic acid—CH3-COOH

where CH2 is added between methyl group and carboxylic acid CH3-CH2-CH2------COOH

Eg. Stearic acid CH3(CH2)14COOH

Palmitic acid

Saturated fatty acids of less than eight carbon atoms are liquid at physiological temperature

Dr. Siham Gritly 21

• Saturated fatty acids:– Lauric acid 12:0– Myristic acid 14:0– Palmitic acid 16:0– Stearic acid 18:0

Palmitic acid

Dr. Siham Gritly 22

• Unsaturated fatty acids; contain one or more double bond

• Eg. Oleic acid CH3(CH2)7CH=CH(CH2)COOH

• Linolenic acid 18:2 • Mono-ployunsaturated fatty acids • Unsaturated fatty acids:

– Palmitoleic acid 16:1– Oleic acid 18:1

Dr. Siham Gritly 23

saturated and unsaturated fatty acids

CH3(CH2)14COOH CH3(CH2)7CH=CH(CH2)COOH

Dr. Siham Gritly 24

Mono-unsaturated fatty acidcontain one carbon double bond

Dr. Siham Gritly 25

Polyunsaturated two or more carbon atoms are double bonded,

Dr. Siham Gritly 26

delta ∆ and omega ω systems

• Delta and omega systems are other nomenclature of fatty acids

• The delta ∆ system the notation describe the chain length and the number and position of the double bonds

• The linoleic acid notation is 18:2 ∆9, 12• This means 18 carbon in the chain, 2 double bond at

position 9 and 12 • In delta numbering start from the carboxyl end of the

fatty acid

Dr. Siham Gritly 27

α-Linolenic acid (ALA) 18:3Δ9,12,15 (no-3) Essential fatty acid; An omega-3

polyunsaturated fatty acid

Arachidonic acid 20:4Δ5,8,11,14 An omega-6 polyunsaturated fatty acid

Precursor for eicosanoid synthesis

delta ∆ and omega ω systems

Dr. Siham Gritly 28

• Omega system ω counts from the methyl end of fatty acid hydrocarbon chain; the notation for linoleic acid is 18:2 ω 6 or 18:2 n 6

• This means that carbon number of linoleic acid is 18 and 2 indicates the number of double bond in position 6 counting from methyl group end of the carbon chain

• The suggestion is that; The double bond in fatty acid always separated by three carbon so if the location of double bond of omega number one known the other double bond will be known

Dr. Siham Gritly 29

• Some examples;-• Palmitoleic acid 16:1 ∆9 or 16:1 ω 7 or (n-7)• Oleic acid 18:1 ∆9 (n-9) • α-Linolenic acid (ALA) 18:3Δ9,12,15• Linoleic acid 18:2 ∆9, 12 (n-6)• Arachidonic acid 20:5 ∆5,8,11,14 (n-6) • Eicosapentaenoic acid 20:5 ∆5, 8, 11 14, 17 (n or

ω 3 • Docosahexaenoic acid 22:6 ∆4,7,10,13,16,19

Dr. Siham Gritly 30

Omega-3 (ω3) and omega-6 (ω6) fatty acids

• Omega-3 (ω3) and omega-6 (ω6) fatty acids are unsaturated "Essential Fatty Acids" (EFAs) that need to be included in the diet because the human metabolism cannot create them from other fatty acidsAlpha-linolenic acid is an omega-3 fatty acid because it has a double bond three carbons away from the "omega" carbon

Dr. Siham Gritly 31

Physiologically Relevant Fatty Acidsadapted from 1996–2012 themedicalbiochemistrypage.org, LLC | info

@ themedicalbiochemistrypage.org

Numerical SymbolCommon

Name Struture Comments

Myristic acid

14:0

Often found attached to the N-term. of plasma

membrane-associated cytoplasmic proteins

Palmitic acid

16:0

End product of mammalian fatty acid synthesis

Stearic acid18:0

Dr. Siham Gritly 32

Physiologically Relevant Fatty Acidsadapted from 1996–2012 themedicalbiochemistrypage.org, LLC | info

@ themedicalbiochemistrypage.org

Oleic acid

18:1Δ9

An omega-9 monounsaturated fatty

acid

Linoleic acid

18:2Δ9,12

Essential fatty acidAn omega-6 polyunsaturated

fatty acid

Dr. Siham Gritly 33

Physiologically Relevant Fatty Acidsadapted from 1996–2012 themedicalbiochemistrypage.org, LLC | info @

themedicalbiochemistrypage.org

α-Linolenic acid (ALA)

18:3Δ9,12,15

Essential fatty acidAn omega-3

polyunsaturated fatty acid

Arachidonic acid

20:4Δ5,8,11,14

An omega-6 polyunsaturated fatty acid

Precursor for eicosanoid synthesis

Eicosapentaenoic acid (EPA)

20:5Δ5,8,11,14,17

An omega-3 polyunsaturated fatty acid

enriched in fish oils

Docosahexaenoic acid (DHA)

22:6Δ4,7,10,13,16,19

An omega-3 polyunsaturated fatty acid

enriched in fish oils

Dr. Siham Gritly 34

More examples

Dr. Siham Gritly 35

Orientation of Cis and trans bond of unsaturated fatty acids

• The steric geometry of unsaturated fatty acids can also vary such that the acyl groups can be oriented on the same side or on opposite sides of the double bond.

• A cis configuration; hydrogen atoms are on the same side of the double bond. The more double bonds the chain has in the cis configuration, the less flexibility it has

• cis bonds limit the ability of fatty acids to be closely packed, and therefore could affect the melting temperature of the membrane or of the fat

Dr. Siham Gritly 36

• A trans configuration, means that the next two hydrogen atoms are bound to opposite sides of the double bond. As a result, they do not cause the chain to bend much, and their shape is similar to straight saturated fatty acids

Dr. Siham Gritly 37

Cis Configuration and Trans Configuration When the acyl groups are both on the same side of the double bond it is referred to as a cis bond, such as is the case for oleic acid (18:1). When the acyl groups are on opposite sides the bond is termed trans such as in elaidic acid, the trans isomer of oleic acid

Cis Configuration Trans Configuration

Dr. Siham Gritly 38

Trans (Elaidic acid) the trans isomer of oleic acid Elaidic acid is the principal trans unsaturated fatty acid

often found in partially hydrogenated vegetable oils

Dr. Siham Gritly 39

Cis Oleic acid is a cis unsaturated fatty acid that has one double bond, "bend or

curve. it comprises 55–80% of olive oil

Dr. Siham Gritly 40

Glycerol C3H8O3

• Glycerol has three hydroxyl group attached to each C atom ( alcohol) that are responsible for its solubility in water

• The glycerol backbone is central to all lipids known as triglycerides

Dr. Siham Gritly 41

Lipids and fats present in the body in three different forms

• 1-neutral fats (triglycerides)

• 2-cholesterol (present only in animal origin)

• 3-phospholipids (largest lipid components in the body)

Dr. Siham Gritly 42

1-Triglycerides

• Triglycerides are the main dietary fats in human body. It is a naturally occurring ester of three fatty acids and glycerol that is the chief constituent of fats and oils

• Triglycerides are alcohol glycerol (hydroxyl group HO-) and three fatty acids (carboxyl group COOH).

Dr. Siham Gritly 43

• In triglycerides, the hydroxyl groups of the glycerol join the carboxyl groups of the fatty acid to form ester bonds

• Ester bond a compound formed from an alcohol and an acid by removal of water

Dr. Siham Gritly 44

Basic Structure of TriacylglyceridesTriglycerides consists of three fatty acids and

glycerol

Dr. Siham Gritly 45

• The main fatty acids ;• 1-stearic acid a (saturated fatty acid)• 2-oleic acid (unsaturated one double bond,

olive)• 3-palmitic acid (saturated, poultry, beef, milk,

palm oil)

Dr. Siham Gritly 46

Lipids are stored as triacylglycerol in adipose tissues , three fatty acids are joined to glycerol by an ester

linkage

Dr. Siham Gritly 47

triglyceride

Dr. Siham Gritly 48

One molecule of the alcohol, glycerol Attached to the glycerol (by dehydration synthesis) are 3 fatty acids. The fatty acids determine the characteristics or properties of the fat. The bond formed between the –OHs of the alcohol and the carboxyl COOH of the fatty acid is an ester bond

Dr. Siham Gritly 49

2-cholesterol

• *Are member of groups called sterols, it is alcohol found only in tissues and cells of animals' origin.

• Sterols (Steroids) are composed of hydrocarbon chains with four interconnected rings.

Dr. Siham Gritly 50

Cholesterol is a lipid (fat) which is produced by the liver. Cholesterol is vital for normal body function. Every cell in our body has cholesterol in its outer layer

Dr. Siham Gritly 51

• *main function of cholesterol;

• It enter in the formation of bile acids,• *Essential component of the structural membranes

of all cells especially brain and nerve cells• *They form a part of certain enzymes• *Enter in the formation of steroid hormones such as

esterogens, progesterone and testosterones • *Enter in the formation of vitamin D.

Dr. Siham Gritly 52

The structure of sterols is very different from that of the long carbon chains seen in fatty acids and phospholipids.The carbons in the structure of sterol are mostly arranged in many rings

Dr. Siham Gritly 53

steroid hormones esterogens, progesterone and testosterones

Dr. Siham Gritly 54

3-phospholipids

• *phospholipids are any lipids containing phosphorus. they are the largest lipid components of the body after triglycerides. Most phospholipids additional to phosphate containing choline

• *they form in all cells of the body • *in plasma, they are present in combination

with proteins and lipoproteins, which evolved in transport of fat and cholesterol

Dr. Siham Gritly 55

• *they form part of certain enzymes• *main constituents of all cell membranes• Phospholipids; a group called CHNOPS, or the

six elements of life: • Carbon, Hydrogen, Nitrogen, Oxygen,

Phosphorus, Sulfur

Dr. Siham Gritly 56

The basic structure of phospolipids phospholipids are similar to fats, except they contain a phosphorous group and two fatty acids instead of three

Dr. Siham Gritly 57

Functions of phospholipids

• 1. Act as building blocks of the biological cell membranes in almost all organisms, form the outer cell membrane and help the cell maintain its internal structures.

2. Participate in the transduction of biological signals across the membrane.

3. Act as efficient store of energy as with triglycerides..

Dr. Siham Gritly 58

• 4. Play an important role in the transport of fat between gut and liver in mammalian digestion.

5. An important source of acetylcholine which is the most commonly occurring neurotransmitter substance Peripheral nervous system (PNS) and central nervous systems (CNS) occurring in mammals

Dr. Siham Gritly 59

Phospolipids; consisting of a water-soluble head and a fat-soluble tailContain phosphorous Component of cell membranes Serve as emulsifiers (allow fats and water to mix and travel in and out of cells into watery fluid on both sides

Dr. Siham Gritly 60

example of phospholipids in the body

• -lecithin; neurotransmitter consist of glycerol, fatty acids, phosphoric acid and cholin (nitrogen-containing base). found in liver, egg yolk, soy beans. the main function; transport and utilization of fatty acids with the action of enzyme as well as it prevent mental retardation.

• *cephalins; for blood clotting (thromboplastin)• *sphingomyelins; nerve tissues and brain, function act

as insulator around the verve fibers, found in egg yolk, liver.

• *glycolipids; serve tissues, cell membranes and help in fat transport.

Dr. Siham Gritly 61

The structure of phospholipids is very similar to that of triglycerides, except a fatty acid is replaced with a compound that contains the mineral phosphorus and often has nitrogen attached

Dr. Siham Gritly 62

The benefit of the phospholipid structure is that the phosphate region makes the molecule highly amphipathic, ideal for the cell membrane structure Hydrophilic portion in the phosphate regionHydrophobic portion in the fatty acid

63

Phospholipids are major component of all cell membrane as they can form lipid bilayers. Most

phospholipids contain a diglyceride a phosphate group and choline

Dr. Siham Gritly

Dr. Siham Gritly 64

Dr. Siham Gritly 65

Phospholipid bilayers form the protective layer around cells

Dr. Siham Gritly 66

Exercise 3; Fat digestion

A. DigestionB. EmulsificationC. Absorption

Dr. Siham Gritly 67

References• Murry K. Robert, Granner K. daryl, Mayes A. peter, Rodwell W. Victor (1999). Harpers

Biochemistry. Appleton and Lange , twent fifth edition

• © 1996–2012 themedicalbiochemistrypage.org, LLC | info @ themedicalbiochemistrypage.org

• Sareen Gropper, Jack Smith and James Groff, Advanced Nutrition and Human Metabolism, fifth ed. WADSWORTH

• Melvin H Williams 2010; Nutrition for Health, Fitness and Sport. 9th ed, McGraw Hill• • Heymsfield, SB.; Baumgartner N.; Richard and Sheau-Fang P. 1999. Modern

Nutrition in Health and Disease; Shils E Maurice, Olson A. James, Shike Moshe and Ross A. Catharine eds. 9th edition

• Guyton, C. Arthur. 1985. Textbook of Medical Physiology. 6th edition, W.B. Company

Dr. Siham Gritly 68

• Lehninger. Principles of bochemistry. by Nelson and Cox, 5th Edition; W.H. Freeman and Company

• Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. ISBN 978-0-19-960563-7.

• Koppenol, W. H. (2002). "Naming of New Elements (IUPAC Recommendations 2002)" (PDF). Pure and Applied Chemistry 74 (5): 787–791. doi:10.1351/pac200274050787. http://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf.

• What Are the Primary Functions of Phospholipids? | eHow.com http://www.ehow.com/facts_7349125_primary-functions-phospholipids_.html#ixzz2FzYc7HnG

Dr. Siham Gritly 69

• Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall

• A. Burtis, Edward R. Ashwood, Norbert W. Tietz (2000), Tietz fundamentals of clinical chemistry

• Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. pp. 52–59

• Maitland, Jr Jones (1998). Organic Chemistry. W W Norton & Co Inc (Np). p. 139. ISBN 0-393-97378-6.

• Nelson DL, Cox MM (2005). Lehninger's Principles of Biochemistry (4th ed.). New York, New York: W. H. Freeman and Company.

• Matthews, C. E.; K. E. Van Holde; K. G. Ahern (1999) Biochemistry. 3rd edition. Benjamin Cummings.

• http://wiki.answers.com/Q/What_is_dehydration_synthesis#ixzz2BuiK645

Dr. Siham Gritly 70