Metabolism USMLE Step 1 Practice Question
A 34-year-old woman with a history of malabsorption presents with progressive fatigue, paresthesias, and impaired wound healing over 3 months. Laboratory studies reveal low serum albumin and fat-soluble vitamin deficiencies. A muscle biopsy shows abnormal mitochondrial morphology and impaired oxidative metabolism. An investigator studying her metabolic dysfunction focuses on the first committed step of the citric acid cycle, where acetyl-CoA condenses with oxaloacetate to form citrate. This reaction is catalyzed by citrate synthase. Which of the following vitamins is an essential component of the cofactor required for this enzyme-catalyzed reaction?
Answer choices
- AThiamine (vitamin B1)
- BPantothenic acid (vitamin B5)Correct answer
- CCobalamin (vitamin B12)
- DNiacin (vitamin B3)
- ERiboflavin (vitamin B2)
- FPyridoxine (vitamin B6)
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