The fatty acids are the basic units of lipid molecules. Fatty acids are derivatives of aliphatic hydrocarbon chain that contains a carboxylic acid group. Over 200 fatty acids have been isolated from various lipids. They differ among themselves in hydrocarbon chain length, number and position of double bonds as well as in the nature of substituents such as oxy-, keto-, epoxy groups and cyclic structure. Depending on the absence, or presence of double bonds, they are classified into saturated and unsaturated fatty acids.
Saturated fatty acids, do not contain double bonds. The hydrocarbon chain may contain 12 to 18 carbon atoms. eg. palmitic and stearic acids
CH3 (CH2)14 COOH - Palmitic acid (C-16)
CH3 (CH2)16 COOH - Stearic acid (C-18)
Unsaturated fatty acids are classified into different types depending on the number of double bonds present in the hydrocarbon chain. These fatty acids are mainly found in plant lipids.
Oleic acid 1
Linoleic acid 2
Linolenic acid 3
Arachidonic acid 4
Fatty acids required in the diet are called essential fatty acids (EFA). They are not synthesized by the body and are mainly polyunsaturated fatty acids (PUFA).
eg. Linoleic acid
They are required for membrane structure and function, transport of cholesterol, formation of lipoproteins and prevention of fatty liver.
The deficiency of essential fatty acid results in phrynoderma or toad skin.