Answer: Organic acids, which are more oxidized than carbohydrates and release relatively more CO 2 per O 2 consumed.
- A Proteins mainly, since amino acid oxidation usually yields RQ above 1 in typical laboratory settings
- B Fats, since their high hydrogen content raises the RQ above 1 under normal conditions as generally observed
- C Pure carbohydrates, since glucose oxidation usually gives an RQ above 1 as frequently documented in most reference accounts
- D Organic acids, which are more oxidized than carbohydrates and release relatively more CO<sub>2</sub> per O<sub>2</sub> consumed
Correct answer: D. Organic acids, which are more oxidized than carbohydrates and release relatively more CO<sub>2</sub> per O<sub>2</sub> consumed
Explanation: Organic acids are already partially oxidized, so their respiration releases relatively more CO<sub>2</sub> per O<sub>2</sub> consumed, giving an RQ greater than 1; pure carbohydrate respiration gives RQ = 1, and fat/protein respiration gives RQ less than 1.
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.