More than 500 naturally occurring amino acids are known to constitute monomer units of peptides, including proteins, as of 2020 although only 22 appear in the genetic code, 20 of which have their own designated codons and 2 of which have special coding mechanisms: Selenocysteine which is present in all eukaryotes and pyrrolysine which is present in some prokaryotes. The elements present in every amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) ( CHON) in addition sulfur (S) is present in the side chains of cysteine and methionine, and selenium (Se) in the less common amino acid selenocysteine.
Structure of a generic L-amino acid in the 'neutral' form needed for defining a systematic name, without implying that this form actually exists in detectable amounts either in aqueous solution or in the solid state.Īmino 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.
