Amino acid

Written By: Ehsan Jahandarpour

Amino acids are organic compounds that contain amino (−NH+3) and carboxylate −CO−2 functional groups, along with a side chain (R group) specific to each amino acid. The elements present in every amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N); in addition sulfur (S) is present in the side chains of cysteine and methionine, and selenium (Se) in the less common amino acid selenocysteine. More than 500 naturally occurring amino acids are known to constitute monomer units of peptides, including proteins, as of 2020 (though only 20 appear in the genetic code, plus selenocysteine, which is encoded in a special way).