Question

Precursor for corticosteroids synthesis is:

• A. Phenanthrene
• B. 1,2-Cyclopentophenanthrene
• C. 1,2-Cyclopentodihydrophenanthrene
• D. Cholesterol

Answer 1

The Correct Option is D

The correct option is (D): Cholesterol.

Answer 2

The question asks for the precursor molecule from which the body builds corticosteroids. Let's look at each option.

1. Phenanthrene: This is a simple aromatic hydrocarbon made of three fused benzene rings. It is not a compound the human body uses as a starting material for hormone synthesis.
2. 1,2-Cyclopentophenanthrene: This name describes the four-ring skeleton common to all steroid molecules, the steroid nucleus. It is a way of naming the ring system, not an actual substance the adrenal gland converts into hormones.
3. 1,2-Cyclopentodihydrophenanthrene: This is the fully saturated version of the same ring skeleton. Like the option above, it describes steroid ring geometry rather than naming a real biosynthetic starting material.
4. Cholesterol: This is the actual molecule the adrenal cortex uses to build corticosteroids. An enzyme called desmolase cleaves the side chain of cholesterol to form pregnenolone, the common first step from which cortisol, aldosterone and other corticosteroids are made.

Only cholesterol is a real compound present in the body that gets converted step by step into corticosteroids, while the other options are just names for the steroid ring pattern.

Therefore, the correct answer is Cholesterol.