Which vitamin is essential for blood clotting?
Answer and explanation
Correct answer: A. Vitamin K
- Step 1: The coagulation cascade requires the post-translational -carboxylation of glutamic acid residues on specific procoagulant proteins.
- Step 2: Vitamin K (phylloquinone/menaquinone) is the indispensable enzyme cofactor for -glutamyl carboxylase, enabling the hepatic synthesis of clotting factors II (prothrombin), VII, IX, and X.
Answer
Vitamin K.
Why not the others: 'Vitamin C' (ascorbic acid) is a cofactor for collagen proline/lysine hydroxylases; 'Vitamin A' (retinol) is essential for photoreceptor rhodopsin synthesis and epithelial integrity; 'Vitamin E' (tocopherol) serves as a lipid-soluble chain-breaking antioxidant in cell membranes.
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