<prompt> Melatonin is synthesized fromHistidineMethionineTryptophanPhenylalanine  <response>: Ans. c Tryptophan. Ref. Harper, Biochemistry, 25th pg.355AMINOACID DERIVATIVESPhenylalanine: Phenylalanine tyrosine dopa norepinephrine epinephrine Phenylalanine tyrosine dopa dopamine melanin2 Phenylalanine tyrosine thyroxineTryptophan Niacin Serotonin Melatonin2Histidine Histidine -Histamine by decarboxylationGlycine Porphyrin and haeme Purines Creatine totally madeup of glycine arginine methionine; mnemonic--GAM Glutathione totally made up of glycine cystine glutamate; mnemonic--GCGArginine Carnitine UreaMethionine Choline 