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Concept Check Questions
Chapter 9
Cellular Respiration
9.1 Catabolic pathways yield energy by oxidizing organic fuels
1. In the following redox reaction, which compound is oxidized and which is reduced?
C4H6O5 + NAD+ → C4H4O5 + NADH + H+
9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
1. During the redox reaction in glycolysis (step 6 in figure 9.9 in the orange book), which
molecule acts as the oxidizing agent? The reducing agent?
9.3 The citric acid cycle completes the energy-yielding oxidation of organic molecules
1. In which molecules is most of the energy from the citric acid cycle’s redox reactions
conserved? How will these molecules convert their energy to a form that can be used to
make ATP?
2. What cellular processes produce the carbon dioxide that you exhale?
9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
1. What effect would an absence of O2 have on oxidative phosphorylation (the process
shown in figure 9.15 in the orange book)?
2. In the absence of O2, as above, what do you think would happen if you decreased the pH
of the intermembrane space of the mitochondrion? Explain your answer.
9.5 Fermentation enables some cells to produce ATP without the use of oxygen
1. Consider the NADH formed during glycolysis. What is the final acceptor for its
electrons during fermentation? What is the final acceptor of electrons during respiration?
2. A glucose-fed yeast cell is moved from an aerobic environment to an anaerobic one. For
the cell to continue generating ATP at the same rate, how would its rate of glucose
consumption need to change?
9.6 Glycolysis and the citric acid cycle connect many other metabolic pathways
1. Compare the structure of a fat (see figure 5.11 in the orange book) with that of a
carbohydrate (see figure 5.3 in the orange book). What features of their structures make
a fat a much better fuel?
2. Under what circumstances might your body synthesize fat molecules?
3. What will happen in a muscle cell that has used up its supply of oxygen and ATP? (See
figure 9.20 in the orange book.)