Question

Which one of the following compound is a precursor for the biosynthesis of cholesterol?

• A. Progesterone
• B. Lanosterol
• C. Cholic acid
• D. Coprostanol

Answer 1

The Correct Option is B

To determine which compound serves as a precursor for the biosynthesis of cholesterol, it's essential to understand the biological pathway involved in cholesterol synthesis.

Cholesterol is an important sterol component of animal cell membranes and serves as a precursor for the synthesis of steroid hormones, bile acid, and vitamin D. The biosynthesis of cholesterol occurs through a complex series of pathways known as the mevalonate pathway, which leads to the formation of a key intermediate: lanosterol.

1. The mevalonate pathway begins with acetyl-CoA, resulting in the formation of isopentenyl pyrophosphate (IPP).
2. Through a series of enzymatic reactions, IPP is converted into squalene.
3. Squalene undergoes cyclization to form lanosterol.
4. Lanosterol, through several steps involving demethylation and other modifications, is transformed into cholesterol.

In this pathway, lanosterol represents the first sterol structure and serves as the direct precursor molecule to cholesterol.

Let us now compare the given options:

• Progesterone is a steroid hormone derived from cholesterol, not a precursor for its biosynthesis.
• Lanosterol is indeed the precursor from which cholesterol is synthesized. This makes it the correct answer.
• Cholic acid is a bile acid produced from cholesterol in the liver.
• Coprostanol is a cholesterol derivative found in the feces, resulting from microbial reduction in the gut.

From this analysis, it is clear that the correct answer is:

Lanosterol