Wound healing is markedly impaired in a patient with scurvy. The underlying mechanism is failure of which intracellular step in collagen synthesis?

• A Translation of procollagen alpha chains on ribosomes
• B Cross-linking of tropocollagen by lysyl oxidase
• C Cleavage of terminal propeptides by procollagen peptidase
• D Vitamin C dependent hydroxylation of proline and lysine residues ✓

Explanation

Ascorbic acid is the required cofactor for prolyl and lysyl hydroxylases in the rough endoplasmic reticulum. Without hydroxylation, procollagen alpha chains cannot form a stable triple helix and are degraded, producing defective wound matrix. Propeptide cleavage occurs extracellularly and cross-linking by lysyl oxidase is copper dependent, so those steps are unaffected in scurvy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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