Bacteriology USMLE Step 1 Practice Question
A 30-year-old researcher in a microbiology laboratory adds an antibiotic toxin to isolated mitochondria. Within minutes, ATP production ceases completely, the proton gradient across the inner mitochondrial membrane increases significantly, and electron transport chain activity slows secondarily. Serum lactate is elevated at 4.2 mmol/L, consistent with anaerobic metabolism. The researcher notes that NADH oxidation remains intact. Which of the following mitochondrial complexes is most likely inhibited by this toxin?
Answer choices
- ACytochrome c oxidase
- BATP synthaseCorrect answer
- CNADH dehydrogenase
- DSuccinate dehydrogenase
- EAdenine nucleotide translocase
- FUbiquinol-cytochrome c oxidoreductase
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.