<prompt> Which of the following is the rate limiting enzyme of bile acid synthesisMitochondrial 17 α hydroxylaseCytoplasmic 7 α hydroxylaseMicrosomal 7 α hydroxylaseMitochondrial 7 α hydroxylase.  <response>: Microsomal 7 α hydroxylase cholesterol 7 α hydroxylase is the rate limiting enzyme of bile acid synthesis. This enzyme is expressed only in liver. 