fatty acids.pptx

LIPID TYPES

1. FATTY ACIDS 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

3. Omega 3 Omega 6 Omega 9

4. Classification of fatty acids Depending on total number of carbon atoms Even chain fatty acids: having carbon atoms 2,4,6 & series exapmle : A cetic 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

5. 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

6. 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)

7. 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

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

9. 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

10. 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

11. 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, Octadec anoic acid If one double bond then acid Octadec enoic acid If two double bonds then Octadeca dienoic acid If three double bonds Octadeca trienoic acid. Systematic names are based on IUPAC nomenclature :

12. General Patterns of Double Bonds The most common positions for double bonds are Δ 9, Δ 12, and Δ 15. 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

13. 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

14. 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.

15. C hemical Properties of fatty acids Hydrogenation Halogenation Salt formation Ester formation

16. 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.

17. The Packing of Fatty Acids

18. 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)

19. 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