Answer: NADH produced earlier during glycolysis.
- A ATP generated by the electron transport chain
- B NADH produced earlier during glycolysis
- C CO<sub>2</sub> released from the Krebs cycle reactions
- D Oxygen drawn in from the surrounding air
Correct answer: B. NADH produced earlier during glycolysis
Explanation: In lactic acid fermentation, pyruvate accepts electrons from NADH (generated during glycolysis) and is reduced to lactic acid, regenerating NAD+ for glycolysis to continue.
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.