Answer: Coenzyme A, NAD+, and thiamine pyrophosphate acting together.
- A Coenzyme A, NAD+, and thiamine pyrophosphate acting together
- B Water alone, since the reaction is a straightforward hydrolysis
- C ATP alone, since the reaction is a simple phosphorylation step
- D Oxygen alone, since this is where O<sub>2</sub> is first consumed in respiration
Correct answer: A. Coenzyme A, NAD+, and thiamine pyrophosphate acting together
Explanation: The pyruvate dehydrogenase complex uses multiple cofactors, including thiamine pyrophosphate, coenzyme A, and NAD+, to convert pyruvate into acetyl CoA, releasing CO<sub>2</sub> in the process.
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.