A 3-year-old child presents with follicular hyperkeratosis (goose-flesh skin), perifollicular hemorrhages, and bleeding gums. The mother reports very poor consumption of fresh fruits and vegetables. The deficient nutrient is involved in which enzymatic reaction that explains the perifollicular hemorrhages?
- A Cofactor for lysyl oxidase, which cross-links collagen and elastin
- B Component of coagulation factor VII activation in the extrinsic pathway
- C Cofactor for prolyl and lysyl hydroxylase, essential for collagen triple helix stability ✓
- D Antioxidant preventing peroxidation of vascular endothelial membranes
Explanation
Vitamin C (ascorbic acid) deficiency causes scurvy. Ascorbate is an obligatory cofactor for prolyl hydroxylase and lysyl hydroxylase — enzymes that hydroxylate proline and lysine residues in procollagen, which is essential for the formation of the stable triple helix structure of mature collagen. Without adequate hydroxylation, collagen fibrils are structurally weak, leading to fragile capillaries, perifollicular hemorrhages, poor wound healing, and bone fragility. Lysyl oxidase is a copper-dependent enzyme (relevant to Menkes disease). Vitamin K is required for carboxylation of coagulation factors.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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