Molecular Biology/Genetics USMLE Step 1 Practice Question
A 17-year-old girl presents to the emergency department with fever (39.2°C), tachypnea (RR 28), and tachycardia (HR 112). She reports ingesting a large quantity of aspirin 2 hours ago, followed by vomiting and tinnitus. Arterial blood gas reveals pH 7.28 with elevated lactate (5.2 mmol/L). Despite markedly increased oxygen consumption, her cells generate less ATP while producing excessive heat. She denies recent illness. Which mechanism best explains her altered cellular energy metabolism?
Answer choices
- AUncoupling of oxidative phosphorylation by dissipating the proton gradientCorrect answer
- BInhibition of ATP synthase
- CInhibition of cytochrome c oxidase
- DActivation of glycogen phosphorylase only
- EBlockade of ADP entry into mitochondria
- FInhibition of the citric acid cycle by competitive substrate binding
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