A 7-year-old boy presents with bleeding gums, perifollicular hemorrhages, and poor wound healing following a 6-month restrictive diet. Vital signs show HR 92/min, BP 105/68 mmHg, and RR 18/min. Serum vitamin C is 0.1 mg/dL (normal: >0.6). Skin biopsy from a healing wound demonstrates impaired collagen cross-linking with abnormal fibril formation. He denies joint pain or petechiae. Vitamin C is essential for which biochemical modification of collagen?
- A)Oxidation of cysteine residues in keratin
- B)Cleavage of procollagen by elastase
- C)Hydroxylation of proline and lysine residuesGABARITO
- D)Cross linking of fibrin monomers
- E)Carboxylation of glutamate residues
Explicação
Vitamin C is a cofactor for hydroxylation of proline and lysine residues in collagen. Without adequate hydroxylation, collagen cannot form stable triple helices and proper cross linking, leading to weak connective tissue and defective wound healing in scurvy. Ver explicação completa e trilha adaptativa →