Which metal ion is present in vitamin B₁₂?
- AMg(II)
- BFe(III)
- CZn(II)
- DCo(III)
Show answer and explanation
Correct answer: (d) Co(III)
Explanation
Vitamin B₁₂ (cobalamin) contains cobalt, held at the centre of a corrin ring by four nitrogen atoms. In its active forms, the cobalt is usually in the +3 (Co(III)) state.
It is the only vitamin that contains a metal. It is needed for forming red blood cells, for making DNA and for keeping nerves healthy; its lack causes pernicious anaemia. Magnesium is the central atom of chlorophyll, and iron that of haem.