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': 'Cysteine is synthesized from \nSelect and explain. \nA. Methionine, B. Arginine, C. Histidine, D. Lysine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Methionine is first conveed to active methionine and then it is conveed to cysteine on combining with serine.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 217, Fig 16.14, 16.15.', 'role': 'assistant'}]