Fatty acids - structure and nomenclature

In most PUFA, the double bonds are separated by a methylene (-CH -) group. However this is not always the case, and in some PUFA the double 

Systematic name Trivial name Shorthand notation Sources 

Hexadecanoic Palmitic 16 0 MUk Eggs Animal fats Meat Cocoabutter Palm oU (other vegetable oils contain lesser amounts) Fish oils 

Octadecanoic Stearic 18 0 Milk Eggs Animal fats Meat Cocoabutter 

All-ds9,12,15- Octadecatrienoic a-Linolenic 18 3n-3 Cannot be synthesized in mammals Green leaves Some vegetable oils, espedaUy rapeseed, soybean and linseed oUs 

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Figure 1 Fatty-acid structure and nomenclature. (A) Chemical formula and carbon atom numbering system for a 16-carbon saturated fatty acid (16 0). (B) Schematic representation of 16 0. (C) A monounsaturated fatty add, 18 1n-9, showing the double bond nine carbon atoms from the methyl end (carbon 18). (D) The essential n-6 fatty acid 18 2n-6, where the first double bond is found six carbon atoms from the methyl end. The two double bonds are separated by a methylene (-CH2-) group. (E) The essential n-3 fatty acid 18 3n-3, where the first double bond is found three carbon atoms from the methyl end. (F) Phytanic acid, a dietary / -methyl-branched-chain fatty acid (3,7,11,15-tetramethyl 16 0). The melhyl group on carbon 3 prevents this fatty acid from degradation by /3-oxidation. (G) Pristanic acid (2,6,10,14-tetramethyl 15 0) is the product of phytanic acid o-oxidation, in which a single carbon (carbon 1) is lost. The methyl group on carbon 2 does not preclude subsequent degradation by /3-oxidation.

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