These are due to the carboxyl group and the hydrocarbon chain of fatty acid.

Physical Properties

Depending on the length of carbon chains, fatty acid are categorised into three carbons – short chain with less than six carbons, medium chain with eight to fourteen carbons, and long chain with sixteen to twenty-four carbons.

It starts from the carboxyl carbon which is taken as one. The carbons adjacent to thin (carboxyl C) are 2, 3, 4, and so on, or alternately, α, β, γ, and so on. The terminal carbon containing methyl group is known as ω carbon.

The naming of fatty acid (systemic name) is based on the hydrocarbon from which it is derived. The saturated fatty acids end with a suffix -anoic (e.g. octanoic), while the unsaturated fatty acids end with a suffix -enoic (e.g. octadecaenoic acid). In addition to systemic names, fatty acids have common names which are widely used.

Deficiency in infants and children produces skin lesions like eczema. Diet rich in EFA: Sunflower oil, corn oil, cottonseed oil, peanut oil, egg, and lard

Essential fatty acids are required for the membrane structure and function, transport of cholesterol, function of lipoproteins, prevention of fatty liver, and so on. They are also needed for the synthesis of another important group of compounds, namely eicosanoids. They are important for the growth of the cells and the reproductive function. They prolong clotting…

The fatty acids that cannot be synthesised by the body and, therefore, should be supplied in the diet are known as essential fatty acids (EFA). Chemically, they are polyunsaturated fatty acids (PUFA), namely linoelic acid (18: 2; 9, 12) and linolenic acid (18: 3; 9, 12, 15). Arachidonic acid (20: 4; 5, 8, 11, 14)…

Cyclic acids are fatty acids having a cyclic ring structure containing five carbon atoms. They are unsaturated. Two cyclic acids, hydnocarpic acid and chaulmoogric acids, are of interest because of their presence in chaulmoogric oil, which is used in the treatment of leprosy. The structure of chaulmoorgic acid is shown below:

These are fatty acids which contain double bonds. Iodine values vary according to the degree of unsaturation. They are generally liquid at room temperature; the general formula is CnH2n-1 COOH. Unsaturated fatty acids are further divided according to the degree of unsaturation. Table 4.2 Unsaturated Fatty Acids