Answer: Citric acid.
- A Malic acid
- B Pyruvic acid
- C Citric acid
- D Lactic acid
Correct answer: C. Citric acid
Explanation: The 2-carbon acetyl group joins the 4-carbon oxaloacetate to make 6-carbon citric acid - hence the citric acid cycle.
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.