Amino Acid

Small organic molecule containing the amino group (-NH₂). Amino acids are the fundamental building blocks of proteins. Examples are glycine, glutamic acid, alanine, proline, and arginine. Nature makes use of twenty distinct amino acids to synthesize proteins, which are chains of amino acids bound together by so-called peptide bonds. Short chains are called polypeptides and long chains proteins. Of the twenty natural amino acids, nine are labeled essential as they cannot be synthesized in the body and must be ingested from the food. These are: valine, leucine, lysine, histidine, isoleucine, methionine, phenylalanine, threonine, and tryptophan. In foods, amino acids are especially found bound to proteins but to a certain extent also as free amino acids that can have an effect on taste—for example, glutamic acid, which is the basis for umami. Histidine has a bitter taste.