This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Which of the following is not true about tryptophan? \nSelect and explain. \nA. Involved in niacin synthesis, B. Involved in serotonin synthesis, C. Involved in melatonin synthesis, D. It is a non essential amino acid.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Tryptophan is an essential aminoacid. It is used in the synthesis of Melatonin, serotonin and niacin.', 'role': 'assistant'}]