A
tripeptide is a
peptide consisting of three
amino acids joined by
peptide bonds. The exact nature and function of
proteins is determined by the amino acids present and the order they occur. Simple examples are the tripeptides made by combining either three
glycine molecules or two glycines and one
alanine. The three glycine tripeptide can have only one structure: glycine-glycine-glycine. The other tripeptides can have different orders: glycine-alanine-glycine, glycine-glycine-alanine, and alanine-glycine-glycine. Each is a distinct molecule.