2016 · Q26
Vitamin B12 deficiency causes pernicious anemia. Animals cannot synthesize vitamin B12. Humans must obtain all their vitamin B12 from their diet. The complexing metal ion in vitamin B12 is:
General KnowledgeChemistry
- AMg2+ (Magnesium ion)
- BFe2+ (Iron ion)
- CCo3+ (Cobalt ion)
- DZn2+ (Zinc ion)
Explanation
Vitamin B12 (cobalamin) is unique among vitamins in containing a metal ion at its core: a single cobalt ion in the +3 oxidation state, held in a corrin ring. This is why B12 is also called cobalamin. Magnesium is the central ion of chlorophyll, iron is the central ion of haem, and zinc occurs in enzymes such as carbonic anhydrase, but none of them is in vitamin B12. The complexing ion is Co3+, option (C).