This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'Glycine is used in the synthesis of \nSelect and explain. \nA. Nitric oxide, B. Catecholamines, C. Melanin, D. Purines', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The whole of glycine is incorporated into the purine ring. (C4, C5, and N7)Ref: DM Vasudevan - Textbook of Biochemistry for Medical Students, 7th edition, page no: 212', 'role': 'assistant'}]