Fatty acid is an important constituent of fat. It is a monocarboxylic acid with a hydrocarbon chain. The length of the chain may vary from 2 to 34 carbon atoms. It is obtained by the hydrolysis of fats by acids, alkalis, or enzymes. Almost all the fatty acids found in nature have straight chain and even number of carbon atoms. The chain may be saturated or unsaturated. The commonest fatty acids that occur in nature are palmitic, stearic, and oleic acids. Among these fatty acids, oleic acid is unsaturated.

Fatty acids are carboxylic acids with hydrocarbon side chains. They are the simplest form of lipids.

Occurrence: Fatty acids occur mainly in esterified form as the major constituents of various lipids. They are also present as free fatty acids. Fatty acids of animal origin are much simpler in structure in contrast to those of plant origin, which often contains groups such as epoxy, keto, hydroxy, and cyclopentane rings.