Vitamins and Nutrition USMLE Step 1 Practice Question
A 2-day-old boy delivered at home without routine newborn prophylaxis presents with oozing from the umbilical stump and melena. Vital signs show HR 145 bpm, RR 48/min, BP 58/38 mmHg, temperature 37.2°C. Physical examination reveals no hepatosplenomegaly or petechiae. Laboratory studies show PT 22 seconds (normal 12-14) with normal platelet count and bleeding time. Which of the following biochemical processes is most likely impaired?
Answer choices
- AActivation of plasmin from plasminogen
- BGamma carboxylation of glutamate residues on clotting factorsCorrect answer
- CHydroxylation of proline residues in collagen
- DConversion of homocysteine to methionine
- ESynthesis of platelet thromboxane A2
- FPhosphorylation of prothrombin to form thrombin
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