Question

The precursor of vitamin D3 for animals is:

• A. Cholelesterol
• B. Ergosterol
• C. 7-Dehydrocholesterol
• D. 25-hydroxycholecalciferol

Hint:

Remember:
7-Dehydrocholesterol \(\rightarrow\) Vitamin D3 (Animal skin + UV light).
Ergosterol \(\rightarrow\) Vitamin D2 (Plant/Fungal source + UV light).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Vitamin D exists in two main forms: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). These are synthesized from specific sterol precursors under the influence of ultraviolet (UV) light.

Step 3: Detailed Explanation:
1. 7-Dehydrocholesterol: This is a cholesterol precursor found in high concentrations in the epidermal layers of animal skin. Upon exposure to ultraviolet-B (UVB) radiation, it undergoes a photochemical reaction to form Vitamin D3 (cholecalciferol).
2. Ergosterol: This is the plant-based precursor (found in fungi and plants) that is converted into Vitamin D2 (ergocalciferol) upon UV exposure.
3. 25-hydroxycholecalciferol: This is calcifediol, an intermediate metabolite formed in the liver during the activation of Vitamin D3, and is not the initial precursor.
Therefore, the precursor of Vitamin D3 in animals is 7-dehydrocholesterol.

Step 4: Final Answer
The correct option is (C).