Which is the first intermediate in the conversion of cholesterol to bile acids?: (A) Ergosterol, (B) Lanosterol, (C) 7- hydroxycholesterol, (D) 7- dehydrocholesterol
Answer is C. The first intermediate in the synthesis of bile acids is 7a-hydroxycholesterol. It is catalyzed by the enzyme 7a-hydroxylase, a microsomal CYP450 enzyme, which requires NADPH, oxygen, and vitamin C as cofactors. It is the rate-limiting step in the synthesis of bile acids.