Reading Guide, Pratt and Cornely Chapter 13a
1. What is glycolysis? What is gluconeogenesis?
2. Write the net equation (ignoring water and protons) for glycolysis.
3. How many steps are there in glycolysis? What differentiates the two phases?
4. Write the reaction catalyzed by hexokinase. What did you already learn about hexokinase in
chapter 6? Give a chemical explanation of why this is an irreversible reaction.
5. Write the reaction catalyzed by phosphoglucose isomerase. Assuming that the enzyme acts
primarily as an acid-base catalyst, draw an organic mechanism for the conversion of glucose-6phosphate to fructose-6-phosphate. Does it make sense that this is a near-equilibrium reaction?
6. Write the equation for the reaction catalyzed by phosphofructokinase. Why is it a highly
regulated reaction? What did you already learn about its regulation in chapter 7? What is the
most potent allosteric effector of phosphofructokinase?
7. What are the products of the aldolase reaction? What two key residues are involved in the
enzyme catalyzed reaction of aldolase? Provide a basic mechanism of the aldolase reaction.
8. How can aldolase, catalyzing a reaction with a large positive standard free energy change,
catalyze its reaction in the forward direction?
9. What is the reaction catalyzed by triose phosphate isomerase? Toward which triose is the
equilibrium favored under standard conditions? Under physiological conditions?
10. What is the total ATP cost for getting one molecule of glucose through the energyinvestment phase of glycolysis?
11. What cofactor is needed for glyceraldehyde-3-P dehydrogenase? What is the source of
phosphate? Is the reaction an oxidation or reduction of the carbohydrate? Provide an enzymecatalyzed mechanism for the reaction. What is the role of the cysteine residue?
12. Use the values from Table 12.4 to show that the reaction catalyzed by phosphoglycerate
kinase is -18.8 kJ/mol.
13. What is the structure of the intermediate in the phosphoglycerate mutase catalyzed reaction?
14. What type of reaction is catalyzed by enolase? Write the equation of this reaction.
15. What is the chemical driving force that gives a large standard free energy change to the
reaction of phosphoenolpyruvate with ADP to form ATP and pyruvate?
16. Which three steps of glycolysis are irreversible? Which step is the key regulation step for
glycolysis?
17. once pyruvate is formed, what are four of the molecules it can be made into? What are two
factors that determine pyruvate’s fate/
18. If oxygen is present, the NADH made through glycolysis is reoxidized, but if there is not
enough oxygen in human muscle, how is NADH reformed into NAD+?
19. How is NADH reoxidized by yeast under anaerobic conditions?
20. Write the reaction of pyruvate dehydrogenase. Is pyruvate oxidized or reduced?
21. Pyruvate is a carbon source for making biomolecules such as ...
22. What is biotin’s function in the production of oxaloacetate from pyruvate?