This document discusses fatty acids, which are carboxylic acids and key building blocks for lipids. Fatty acids can be saturated or unsaturated depending on whether they contain single or double carbon bonds. They are classified based on chain length and the number and position of double bonds. Unsaturated fatty acids have lower melting points than saturated fatty acids. Essential fatty acids like omega-3 and omega-6 must be obtained through diet as the human body cannot synthesize them. Fatty acids play important structural and physiological roles.

1. 13-10-2011

2. FATTY ACIDS
• Fatty acids are carboxylic acids with hydrocarbon side
chain
• Simplest form of lipids
• Key building blocks for lipids
• Chains of carbon atoms with a carboxyl group at one
end, and a methyl group at the other
• May be “free” or attached to another compound
• Determine the characteristics of the fat

4. • Omega 3
• Omega 6
• Omega 9

5. Classification of fatty acids
Depending on total number of carbon atoms
1. Even chain fatty acids:
• having carbon atoms 2,4,6 & series
• exapmle: Acetic acid
Butyric acid
Caproic acid
Palmitic acid
2. Odd chain fatty acids:
• having carbon atoms 3,5,7 etc
• Seen in microbial cell walls & also present in milk
• Example: Propanoic
Valeric

6. Cont..
Depending on the length of hydrocarbon chain
• Short chain = 2-6 carbons
• Medium chain = 8-14 carbons
• Long chain = 16 & above, usually up to 24 carbons

7. Depending the nature of hydrocarbon chain
• Saturated fatty acids
• Unsaturated fatty acids
• Branched chain fatty acids (e.g. isovaleric
acid)
• Hydroxy fatty acids (e.g. cerebronic acid)

8. • If all the carbon atoms in the chain are joined
with single bonds, and the remaining bonds are
attached to hydrogen
• Long-chain saturated fatty acids stack tightly
and form solids at room temperature
• Short-chain saturated fatty acids are also liquid
at room temperature
SATURATED FATTY ACID

9. Saturated Fatty Acids
Completely Unbranched and saturated
with no double bonds

11. UNSATURATED FATTY ACID
• If adjoining carbons are joined by double bonds
• One double bond = monounsaturated fatty acid
• Two or more double bonds = poly- unsaturated fatty acid
• Monounsaturated and polyunsaturated fatty acids don’t
stack compactly and are liquid at room temperature

13. Nomenclature of Fatty Acids
COOH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Number of Double Bonds
Position of Double Bonds
Carbon Chain Length
18:3 ( 9, 12, 15)
The most commonly occurring fatty acids have even number of carbon
atoms in an un-branched chain of12-24 carbons

14. CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH
12 11 10 9 8 7 6 5 4 3 2 1
or
CH3 (CH2)10 –COOH Dodecanoic acid (Lauric)
 14:0 tetradecanoic acid
 16:0 Hexadecanoic acid
 20:0 Eicosanoic acid
 22:0 Docosanoic acid
 24:0 Tetracosanoic acid
 No double bonds for eg in 18:0, Octadecanoic acid
 If one double bond then acid Octadecenoic acid
 If two double bonds then Octadecadienoic acid
 If three double bonds Octadecatrienoic acid.
Systematic names are based on IUPAC nomenclature:

15. General Patterns of Double Bonds
 The most common positions for double bonds are
Δ9, Δ12, and Δ15.
 The double bonds of polyunsaturated fatty acids are separated
by methyl group:
-CH=CH-CH2-CH=CH-
 In almost all the naturally occurring unsaturated fatty acids, the
double bonds are in Cis- configuration

16. TWO TYPES OF BOND FORMATION:
• CIS - hydrogens on the carbons joined by a
double bond are on the same side = the carbon
chain is bent
• TRANS – hydrogens on the carbons joined by
a double bond are on the opposite side = the
carbon chain is straighter

18. Physical Properties of Fatty Acids
 The physical properties of fatty acids are largely determined
by the length and degree of unsaturation of the hydrocarbon
chain.
 The longer the chain and the fewer the double bonds, the
lower is the solubility in water, and higher is the melting point.
• Addition of double bonds decreases the melting point
whereas, increasing the chain length increases the melting
point. For example; 4:0 MP -7.9 C, 12:0 MP 44.2 C, 16:0 MP
62.7 C, 18:1 MP 10.5 C, 18:2 MP -5.0 C, 18:3 MP -11 C.

19. Chemical Properties of fatty acids
• Hydrogenation
• Halogenation
• Salt formation
• Ester formation

20. Isomerism
• A double bond in Fatty acid chain permits two types of
geometrical isomers, cis and trans.
• Cis isomers have a curved configuration.
• Trans isomers have a linear configuration.
• Due to curve configuration cis unsaturated fatty acids
have a lower melting point as compared to there trans
counterpart.
• Most of the natural unsaturated fatty acids have cis
double bonds.

21. The Packing of Fatty Acids

22. Essential fatty acids
• The fatty acids that can not be synthesized by the
body, & therefore, should be supplied in the diet
is known as essential fatty acids
• Chemically, they are polyunsaturated
• Example:
- Linoleic acid (18:2,9,12)
- Linolenic acid (18:3,9,12,15)
- Arachidonic acid (20:4,5,8,11,14)

23. Function of EFA
• Structural elements of tissue
• Structural elements of gonads
• Synthesis of prostaglandins and other compounds
• Structural components of mitochondrial membrane
• Serum level of cholesterol
• Effect on clotting time
• Effect on fibrinolytic activity
• Role of EFA in fatty liver
• Role in vision