This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Which of the following aminoacid in a protein is involved in urea cycle and is required for synthesis of NO? \nSelect and explain. \nA. Arginine, B. Histidine, C. Tryptophan, D. Lysine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. ArginineFallowing are required for Nitric Oxide (NO) synthesis: Arginine, NO synthase, Ca++_and NADPH.Urea cycle:', 'role': 'assistant'}]