zwitterion amino acid organic molecular entity polar amino acid zwitterion 74.024 74.05870 C2H4NO2R CHEBI:62031 MetaCyc:Polar-amino-acids Zwitterionic form of a polar amino acid having an anionic carboxy group and a protonated amino group. [NH3+]C([*])C([O-])=O a polar amino acid chebi_ontology