Acid

Acids play an intregral role in the metabolic functions of animals, in chemistry, material science and the food industry. Acids such as the twenty common amino acids, which are carboxylic acids, valeric acid, proponoic acid and many others are necessary for life. Although acids are most often thought of as proton (H⁺) or hydronium ion ([H₃O]⁺ donors, as defined by the Brønstad-Lowry theory, the Lewis acid-base theory is more comprehensive and defines acids as electron pair acceptors.