Which enzymatic step of collagen synthesis is directly impaired in vitamin C deficiency, leading to poor wound healing?

• A Hydroxylation of proline and lysine residues ✓
• B Cleavage of signal peptides from procollagen chains
• C Cross-linking of mature collagen by lysyl oxidase
• D Conversion of tropocollagen microfibrils into fibres

Explanation

Ascorbic acid is the required cofactor for prolyl and lysyl hydroxylases, enzymes that hydroxylate proline and lysine in procollagen. Without this step the triple helix is unstable at body temperature and is not secreted properly, producing the defective collagen of scurvy. Lysyl oxidase cross-linking depends on copper, not vitamin C, which makes option C the strongest distractor.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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