Question

Which of these rings is found in structure of vitamin K?

• A. Naphthoquinone
• B. Iso-alloxazine
• C. Chromane
• D. Pyridine

Hint:

Remember the unique chemical structures of fat-soluble vitamins:
- Vitamin E contains a Chromane ring.
- Vitamin K contains a Naphthoquinone ring.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Fat-soluble and water-soluble vitamins are built around specific aromatic or heterocyclic ring structures that dictate their biochemical properties.

Step 2: Detailed Explanation:
Let us identify the core ring structures of the given options:
1. Naphthoquinone ring (A): Form the hydrophobic core of Vitamin K (specifically, 2-methyl-1,4-naphthoquinone). This structure is essential for its role as a cofactor in blood coagulation.
2. Iso-alloxazine ring (B): Found in Riboflavin (Vitamin \(\text{B}_2\)), where it participates in redox reactions.
3. Chromane ring (C): Found in Tocopherol (Vitamin E).
4. Pyridine ring (D): Forms the core of Pyridoxine (Vitamin \(\text{B}_6\)).
Therefore, the naphthoquinone ring is found in Vitamin K.

Step 3: Final Answer:
The correct option is 1, which corresponds to Naphthoquinone.