fatty acid (FA) [AS, faett + L, acidus, sour] , any of several organic acids produced by the hydrolysis of neutral fats and consisting of a long hydrocarbon chain ending in a carboxyl group. The hydrocarbon chains may be fully saturated or contain varying degrees of unsaturation (exhibited by C=C bonds). In cells, fatty acids usually occur in combination with another molecule rather than in a free state. Essential fatty acids, including linoleic acid and linolenic acid, are unsaturated molecules that cannot be produced by the body and must therefore be included in the diet. See also saturated fatty acid, unsaturated fatty acid.
