Tripeptides are amino acids polymers in which three individual amino acid units, called residues, are linked together by amide bonds. glycine (NH2​−CH2​−COOH), alanine ​CH3​−NH2​C∣H​​−COOH​ and phenyl alanine ​C6​H5​−CH2​−NH2​C∣H​​HCOOH​ can be linked in six different ways.