Answer: Blocking cytochrome oxidase, the terminal enzyme of the electron transport chain.
- A Blocking cytochrome oxidase, the terminal enzyme of the electron transport chain
- B Competing with glucose for the active site of hexokinase in glycolysis according to most studies
- C Inhibiting ATP synthase directly at the F<sub>0</sub> proton channel as widely reported
- D Preventing pyruvate from entering the mitochondrial matrix in the majority of documented cases
Correct answer: A. Blocking cytochrome oxidase, the terminal enzyme of the electron transport chain
Explanation: Cyanide binds and inhibits cytochrome c oxidase (Complex IV), the terminal enzyme of the electron transport chain that transfers electrons to oxygen, halting ATP production via oxidative phosphorylation.
Aerobic respiration unfolds in three locations: glycolysis in the cytoplasm yields a small amount of ATP directly, the Krebs cycle in the mitochondrial matrix harvests electron carriers (NADH, FADH2), and the electron transport chain in the inner mitochondrial membrane uses those carriers to generate the bulk of the ATP, with O2 needed only at this final stage.
Concept context
Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.