This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Biochemistry
[{'content': 'Amino Acid having role in sleep wake cycle: \nSelect and explain. \nA. Tryptophan, B. Phenylalanine, C. Glycine, D. Glutamine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: TRYPTOPHAN METABOLISM USE IN - (1)Serotonin, melatonin synthesis Fig:- Synthesis of serotonin and melatonin Use of serotonin - neurotransmitter responsible for mood elevation, git motility, temp. regulation Excretory end product - 5 hydroxy indole acetic acid (increase in urine in carcinoid syndrome) Melatonin synthesized in pineal gland Responsible for biological rhythm in body', 'role': 'assistant'}]