Question

Precursor for corticosteroids synthesis is:

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

Hint:

Cholesterol is the primary precursor for all steroid hormones, including corticosteroids. Focus on its role in the adrenal cortex for hormone synthesis.

Answer 1

The Correct Option is D

Step 1: Understanding corticosteroid synthesis. Corticosteroids are a class of steroid hormones produced in the adrenal cortex. They are derived from cholesterol, which serves as the precursor molecule. 

Step 2: Role of cholesterol in corticosteroid biosynthesis. Cholesterol undergoes enzymatic modifications to form pregnenolone, the first committed step in the biosynthesis of corticosteroids. This pathway eventually leads to the production of hormones like cortisol and aldosterone. 

Step 3: Incorrect options. - Phenanthrene and its derivatives are not precursors for corticosteroids. 
- Cholesterol's unique structure, a sterol with a hydroxyl group, makes it the ideal precursor.

Answer 2

The question asks which molecule serves as the starting material for making corticosteroids in the body. Let's check each option's actual role in steroid chemistry.

1. Phenanthrene: This is a three-ring aromatic hydrocarbon that shares part of the basic ring skeleton found in steroids, but it is a simple hydrocarbon and is not the molecule the body actually starts from when building corticosteroids.
2. 1,2-Cyclopentophenanthrene: This four-ring skeleton is the core structure common to all steroids, but on its own it is a bare hydrocarbon framework, not a biologically available precursor molecule the body uses to begin steroid synthesis.
3. 1,2-Cyclopentodihydrophenanthrene: Like the fully aromatic version, this is a description of the steroid ring skeleton in structural chemistry, not an actual biosynthetic starting compound found circulating in the body.
4. Cholesterol: Cholesterol is a sterol built on the same four-ring skeleton described above, but with the functional groups the body actually needs, including a hydroxyl group, to begin enzymatic conversion. In the adrenal cortex, cholesterol is taken up and converted step by step, first to pregnenolone and then onward to cortisol, aldosterone, and other corticosteroids.

The other three options only describe the bare ring skeleton shared by all steroids, while cholesterol is the actual molecule the adrenal gland uses as raw material.

So the correct answer is Cholesterol.