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': 'The amino acid at the reducing end of glutathione: \nSelect and explain. \nA. Glycine, B. Cysteine, C. Lysine, D. Glutamate', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]