Fatty Acids

Carboxylic acids with hydrocarbon side chain

GENERAL FORMULA

R ̶ COOH

R

• Hydrocarbon Chain

COOH

• Carboxyl Group

CLASSIFICATION DEPENDING ON NUMBER OF CARBON ATOMS EVEN CHAIN ODD CHAIN DEPENDING ON LENGTH OF HYDROCARBON CHAIN SHORT CHAIN FATTY ACIDS MEDIUM CHAIN FATTY ACIDS LONG CHAIN FATTY ACIDS VERY LONG CHAIN FATTY ACIDS DEPENDING ON NATURE OF HYDROCARBON CHAIN SATURATED FATTY ACIDS UNSATURATED FATTY ACIDS BRANCHED CHAIN FATTY ACIDS HYDROXY FATTY ACIDS

NOMENCLATURE Naming of fatty acid is based on the hydrocarbon from which it is derived.

Saturated acids end with suffix -anoic, e.g. octanoic acid,

Unsaturated acids with double bonds end with suffix -enoic, e g, octadecenoic acid (oleic acid).

Carbon atoms are numbered from the carboxyl carbon .(carbon No. 1)

NOMENCLATURE

Carbon atoms adjacent to the carboxyl carbon (Nos. 2, 3, and 4) are also known as the α, β and γ carbons, respectively.

Terminal methyl carbon is known as the ω- or n-carbon.

γ β α

CH3-CH2-CH2-CH2-CH2-COOH

6 5 4 3 2 1

ω1 ω2 ω3 ω4 ω5

NOMENCLATURE

Position of the double bond(s) is indicated by Δ followed by superscript no. indicating the lowered no. C in double bond.

Δ9 indicates a double bond between carbons 9 and 10 of the fatty acid.

ω9 indicates a double bond on the ninth carbon counting from the ω-carbon.

18:1;9 or Δ9 18:1 CH3(CH2)7CH= CH(CH2)7COOH

ω9,C 18:1 or n-9, 18:1 CH3CH2CH2CH2CH2CH2CH2CH2CH= CH(CH2)7COOH OLEIC ACID

SATURATED FATTY ACIDS

UNSATURATED FATTY ACIDS

UNSATURATED FATTY ACIDS

UNSATURATED FATTY ACIDS

PROPERTIES OF FATTY ACIDS MELTING POINT Melting point of saturated F.A is high as compared to

unsaturated F.A HYDROGENATION .

Production of saturated F.A by adding hydrogen at double bonds.

HALOGENATION Halogens are added to double bond of unsaturated F.A SALT FORMATION Sodium and potassium salt of long chain fatty acids are soap.

PROPERTIES OF FATTY ACIDS DETERGENT FORMATION Reduction of carboxyl group of F.A produce alkyl alcohol which

can be sulfated or sulfonated to form alkyl sulfates or sulfonates that act as detergents

ESTER FORMATION Esters are combination of fatty acids & alcohol. Glycerol+ F.A → monoacyl glycerol Monoacyl glycerol+ F.A → diacyl glycerol EICOSANOIDS FORMATION Important physiological & therapeutic agents formed by 20 C

containing polyunsaturated F.A OXIDATION OF FATTY ACIDS β oxidation Auto oxidation•

GEOMETRIC ISOMERISM Geometric isomerism occurs in unsaturated fatty acids

Depending on the orientation of atoms or groups around the axes of double bonds, which do not allow rotation.

Two types of geometric isomerism are CIS FORM

TRANS FORM

GEOMATRIC ISOMERISM

CIS FORM Acyl chain is on same side of double bond. Found in naturally occuring unsaturated F.A. Give variety of configuration to F.A. Significance for molecular packing. Phospholipids structure Arachidonic acid is U shape.

Oleic acid ̶ L shape

GEOMATRIC ISOMERISM

TRANS FORM Acyl chain is on opposite side of double bond.

Arise from action of microorganisms in rumen.

By product of hydrogenation or hardening.

Eliadic acid ̶ straight

GEOMATRIC ISOMERISM

HARMFUL EFFECTS OF TRANS FATTY ACIDS Formation of trans fatty acids. Major component of baked goods and fried foods. Used in food industry ̶ ↑ shelf life of food. Compete with essential fatty acid. Structurally similar to saturated F.A ̶ promotion of atherosclerosis

& hyperchlosterolemia. ↑ LDL level ,↓ HDL level. ↓ fluidity of membranes. Adversely affect multiple risk factor including, plasma lipids & lipoproteins systemic inflammation endothelial dysfunction insulin resistance diabetes mellitus

ESSENTIAL FATTY ACIDS

• ω6• 18:2; 9,12

LINOLEIC ACID

• ω3• 18:3; 9,12,15

α –LINOLENIC

ACID

Ω6 FATTY ACIDSI. Linoleic acid18:2; 9,12II. γ- Linolenic acid 18:3; 6,9,12III. Arachidonic acid20:4; 5.8,11,14 SOURCES AMDR 10-15% Nuts,avocados,olives,soybean ,various oils including sesame, cotton seed & corn

oil. FUNCTIONS• Lowers plasma cholesterol level• Lowers both plasma HDL & LDL level• Required for fluidity of membrane structure • Required for synthesis of eicosanoids• Deficiency leads to scaly dermatitis, hair loss, degenerative changes in arterial

wall, fatty liver & poor wound healing

I. α-Linolenic acid 18:3; 9,12,15II. EPA(Timnodonic) 20:5; 5,8,11,14,17III. DHA(Cervonic) 22:6; 4,7,10,13,16,19 SOURCES Found with Linoleic acid, fish oils, PL in brain FUNCTIONS• suppress cardiac arrhythmias reduce• ↓ serum TAG levels cardiovascular• ↓tendency for thrombosis mortality• Lower BP• Little effect on LDL & HDL cholesterol level• DHA is present in retinal photoreceptor membrane, Enhances the

electrical response of photoreceptor to illumination.

Ω3 FATTY ACIDS

ESSENTIAL FATTY ACIDS FUNCTIONS OF ESSENTIAL FATTY ACIDS Structural element of tissues. Structural element of gonads. Synthesis of prostaglandin and other compound. Structural element of mitochondrial membrane. Serum level of cholesterol. Effect on clotting time. Role in fatty liver. Role in vision. Preventive role in heart diseases. Fate of EFA ; β-oxidation

ESSENTIAL FATTY ACIDS

WHY ESSENTIAL FATTY ACIDS CAN NOT BE SYNTHESIZED IN BODY?

In animals additional double bonds are introduced only b/w the existing double bond and the carboxyl carbon ̶ COOH, not possible to introduce a double bond b/w the ̶ CH3 group at the opposite & the first unsaturated linkage, so body cannot synthesize an EFA from oleic acid.

Humans have C 9,6,5,4 desaturases but lack the ability to introduce double bonds from C 10 to ω end of the chain.