Answer: Glycolysis, occurring in the cytoplasm.
- A Krebs cycle, occurring in the mitochondrial matrix
- B Glycolysis, occurring in the cytoplasm
- C Oxidative phosphorylation, at the inner membrane
- D Beta oxidation, breaking down fatty acids
Correct answer: B. Glycolysis, occurring in the cytoplasm
Explanation: Glycolysis is the universal first pathway of respiration, breaking down one glucose molecule into two molecules of pyruvate in the cytoplasm.
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.