(a) The general structure of a fatty acid (20). (b) The chemical structure of alpha-linolenic acid (ALA), 18:3n-3. ALA has 18 carbon atoms (C) and 3 double bonds, the first of which is located 3 carbon atoms from the terminal methyl group (omega [ω] end). (c) The molecular structures of dietary omega-6 and omega-3 fatty acids. The presence of a double bond in the hydrocarbon chain of polyunsaturated fatty acids (PUFA) introduces a "kink" in the molecule, creating different secondary structures that influence physical properties (5).