Amino acids are organic compounds containing an amino group (NH₂), a carboxylic group (COOH) and any of various side chain groups. There are twenty amino acids encoded by the genetic code, referred to as the standard amino acids. The basic components of proteins, amino acids form short polymers (meaning a long molecule made up of a chain of smaller, simpler molecules) called peptides or longer polymers called polypeptides or proteins. Additionally, amino acids can function as chemical messengers and as intermediates in metabolism.