Question

Which of the following vitamins perform a coenzyme function?

• A. Vitamine A
• B. Vitamin B
• C. Vitamin C
• D. Vitamin A, B & C

Hint:

Almost all water-soluble vitamins (except C) are coenzymes. Fat-soluble vitamins (A, D, E, K) act more like hormones or specialized molecules (except K, which is a coenzyme for carboxylation).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A coenzyme is a non-protein organic molecule that binds to an enzyme and is essential for its catalytic activity. Many vitamins, particularly those in the water-soluble group, serve as precursors for coenzymes.

Step 2: Detailed Explanation:
The Vitamin B complex (Option 2) is the primary group of vitamins that function as coenzymes. For example, Thiamine (B1) becomes TPP, Riboflavin (B2) becomes FAD, Niacin (B3) becomes NAD, and Pantothenic acid (B5) becomes Coenzyme A. These coenzymes are indispensable for energy metabolism, DNA synthesis, and amino acid metabolism.
Let's look at the others:
- Vitamin A (Option 1) primarily functions in signaling (as retinoic acid) and vision (as retinal), but it is generally not classified as a coenzyme in the standard enzymatic sense.
- Vitamin C (Option 3) acts as a reducing agent (antioxidant) and a cofactor for hydroxylase enzymes (like in collagen synthesis), but it is technically a substrate/cofactor rather than a traditional coenzyme that carries chemical groups between reactions.
Because nearly every B vitamin has a well-defined coenzyme role, "Vitamin B" is the best answer. While Option 4 suggests all do, the specific biochemical definition of a "coenzyme" fits the B vitamins much more rigorously than A or C.

Step 3: Final Answer:
The Vitamin B group is the definitive class of vitamins that act as essential coenzymes in cellular metabolism.