Fatty acids are carboxylic acids with hydrocarbon side chains. They are classified based on the number of carbon atoms and length of the hydrocarbon chain. The document discusses the general structure, classification, nomenclature, properties, essential fatty acids and geometric isomerism of fatty acids. Fatty acids play important structural and physiological roles in the body. Essential fatty acids like omega-3 and omega-6 must be obtained from diet as the human body cannot synthesize them.

1. Fatty Acids

2. Carboxylic acids with hydrocarbon side chain

3. GENERAL FORMULA
R ̶ COOH
R
• Hydrocarbon
Chain
COOH
• Carboxyl
Group

4. 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

5. 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)

6. 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

7. 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

8. SATURATED FATTY ACIDS

9. UNSATURATED FATTY ACIDS

10. UNSATURATED FATTY ACIDS

11. UNSATURATED FATTY ACIDS

12. 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.

13. 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
•

14. 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

15. 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

16. 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

17. GEOMATRIC ISOMERISM

18. 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

19. ESSENTIAL FATTY ACIDS
• ω6
• 18:2; 9,12
• ω3
• 18:3; 9,12,15

21. Ω6 FATTY ACIDS
I. Linoleic acid 18:2; 9,12
II. γ- Linolenic acid 18:3; 6,9,12
III. Arachidonic acid 20:4; 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

22. I. α-Linolenic acid 18:3; 9,12,15
II. EPA(Timnodonic) 20:5; 5,8,11,14,17
III. 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

23. 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

24. 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.