# DBT JRF 2022 — Question 11

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Vitamins & Cofactors · Difficulty: Medium

## Question

Which one of these is a metal containing Vitamin?

## Options

- **A.** Vitamin C
- **B.** Vitamin B1
- **C.** Vitamin B12
- **D.** Vitamin A

## Answer

Option C

## Explanation

Metal-containing vitamin: • Vitamin B12 (Cobalamin) is the only vitamin that contains a metal ion as an integral, essential structural component. • The metal is cobalt ( $\text{Co}^{3+}$ ) at the centre of a corrin ring (similar to haem's porphyrin ring). • The corrin ring coordinates cobalt, and the upper ligand can be a methyl group (methylcobalamin) or adenosyl group (adenosylcobalamin), both active forms. • Cobalamin is essential for methionine synthase (methylation of homocysteine) and methylmalonyl-CoA mutase (propionyl-CoA catabolism). Other vitamins: • Vitamin C: ascorbic acid, no metal • Vitamin B1 (Thiamine): thiazole+pyrimidine, no metal • Vitamin A: retinol, no metal Answer: Vitamin B12 (Option 3).

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