Reading Guide, Pratt and Cornely Chapter 14
1. Is the CO2 you breathe out synthesized from the O2 you breathe in?
2. Why is it better to think of metabolic pathways as a network rather than a pipeline?
3. Give the overall reaction of the pyruvate dehydrogenase reaction. Is it an oxidation or
reduction?
4. List the five coenzymes in the pyruvate dehydrogenase complex, and describe their function.
5. Give the overall reaction equation of the citric acid cycle.
6. From memory, draw the 8 intermediates of the citric acid cycle. Which reactions product
carbon dioxide? Which produce reduced cofactors? Which product substrate level high energy
bonds?
7. Which category of the EC nomenclature does citrate synthase fit into? Write the overall
reaction. Which bond leads to the large negative free energy change for the reaction?
8. What is the structure of isocitrate?
9. Isocitrate has three carboxyl groups—give a chemical rational for why only one eliminated as
carbon dioxide.
10. Is a-ketogluterate dehydrogenase more like isocitrate dehydrogenase or pyruvate
dehydrogenase? Explain.
11. What is substrate level phosphorylation? What is the citric acid cycle reaction that produces a
substrate level phosphorylation? Which high energy bond is made and which is broken in this
reaction?
12. Which cofactor is first reduced by succinate dehydrogenase? Which membrane-bound
cofactor is reduced subsequently?
13. What type of reaction is catalyzed by fumarase?
14. What type of reaction is necessary to transform malate into oxaloacetate? How is this
reaction, with a very positive standard free energy, driven to completion?
15. Provide an accounting of how a glucose molecule can be oxidized to produce 32 ATP under
aerobic conditions.
16. Which three enzymes are regulated in the citric acid cycle?
17. Which of the citric acid intermediates can be used as a carbon source for the formation of
glucose?
18. What is the metabolic purpose of the citrate transport system?
19. What is an anaplerotic reaction?
20. Increasing the concentration of citric acid cycle intermediates increases ________ through
the pathway.