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': 'Beta alanine is a end product of \nSelect and explain. \nA. Cysteine, B. Tyrosine, C. Serine, D. Glycine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: β-alanine is a metabolite of cysteine.', 'role': 'assistant'}]