This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acid Metabolism, Subject name: Biochemistry
[{'content': 'Cysteine is formed from - \nSelect and explain. \nA. Methionine and serine, B. Methionine and glycine, C. Alanine and glycine, D. Serine and glycine', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Methionine and Serine o Cysteine, while not nutritionally essential, is formed from methionine, which is nutritionally essential. Following conversion of methionine to homocysteine , homocysteine and serine form cystathionine, whose hydrolysis forms cysteine and homoserine .o The sulfur of cysteine derives from methionine and the carbon skeleton from serine.", 'role': 'assistant'}]