Arachidonic acid is a 20 carbon omega-6 fatty acid with 4 double bonds. Omega-6 fats are polyunsaturated with the first double-bond beginning with the 6th carbon atom from the methyl end of the molecule. An 18 carbon Omega-3 fatty acid with 3 double bonds. Alpha-linolenic acid is found in flaxseed and other plant oils. Note how just 3 double-bonds alters the chemical structure, making alpha-linolenic acid much more highly folded than an 18 carbon saturated fat.