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': 'Which of the following is the rate limiting enzyme of bile acid synthesis \nSelect and explain. \nA. Mitochondrial 17 α hydroxylase, B. Cytoplasmic 7 α hydroxylase, C. Microsomal 7 α hydroxylase, D. Mitochondrial 7 α hydroxylase.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Microsomal 7\xa0α hydroxylase (cholesterol 7\xa0α hydroxylase) is the rate limiting enzyme of bile acid synthesis. This enzyme is expressed only in liver.', 'role': 'assistant'}]