Objectives for Exam 4
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Regulation of Glycolysis and Gluconeogenesis

1. Which glycolysis reactions require different enzymes for gluconeogenesis? Why?
2. How is skeletal myocyte (muscle cell) hexokinase regulation different from hepatocyte (liver cell) hexokinase regulation? How is regulation in the two cells similar?
3. What is the function of fructose-2,6-bis-phosphate, and how is its concentration controlled?
4. What is the effect on the regulated enzymes of glycolysis of increasing the concentration of
(a) ATP, (b) AMP, (c) glucose or glucose-6-phosphate, (d) acetyl-CoA (AcCoA)
What does each of these modulators indicate about energy conditions in the cell?
5. How do insulin, epinephrine, and glucagon affect glycolysis and gluconeogenesis?
6. What are isozymes, and how do the isozymes of hexokinase differ from each other?
7. How are PFK-1 and FBPase-1 regulated? What conditions promote PFK-1 activity?
8. How are PFK-2 and FBPase-2 regulated? Why is their regulation significant?
9. How is myocyte pyruvate kinase activated or inhibited?
10. How is hepatocyte pyruvate kinase activated or inhibited?
11. What regulated enzymes are affected by insulin, and what are the effects?
12. What regulated enzymes are affected by glucagon, and what are the effects?
13. What regulated enzymes are affected by epinephrine, and what are the effects?

Glycogen Metabolism and Regulation

1. How is glycogen metabolism connected to glycolysis? How are glycogen synthesis and glycogen degradation similar, and how are they different?
2. How is a phosphorylase different from a phosphatase?
3. What are the advantages of regulating glycogen phosphorylase covalently, and how is it regulated covalently?
4. What is the main advantage of regulating glycogen phosphorylase allosterically, and how is it regulated allosterically?
5. How is glycogen synthase regulated?
6. How is blood glucose level related to regulation of glycogen metabolism? How are insulin, epinephrine, and glucagon related to regulation of glycogen metabolism?
7. What is the reaction catalyzed by glycogen phosphorylase, and what type of bond in glycogen is the substrate for glycogen phosphorylase?
8. What is the reaction catalyzed by phosphoglucomutase, and what type of enzyme is it?
9. What do the branching and debranching enzymes do?
10. What are the reactions catalyzed by UDP-glucose pyrophosphorylase and glycogen synthase? What part of glycogen is the substrate for glycogen synthase, and what type of bond does glycogen synthase make?
11. What enzyme covalently modifies glycogen phosphorylase, and what is the effect of the modification? You should use the terms R and T in your answer. How is the regulating enzyme itself regulated?
12. What enzyme covalently modifies glycogen synthase, and what is the effect of the modification?
13. What is the function of protein phosphatase 1 (PP1), and under what conditions is it most active?

Pyruvate Dehydrogenase and the Citric Acid Cycle

1. Why does it matter which coenzymes are prosthetic coenzymes and which are co-substrates?
2. How does TPP assist in decarboxylation by E1?
3. Why is an oxidation-reduction reaction required for pyruvate dehydrogenase? Which coenzymes are oxidized, and which are reduced?
4. What happens to AcCoA in one cycle of the citric acid cycle? What happens to oxaloacetate in the same cycle? How is that possible, given that citrate is a symmetrical molecule?
5. Which reactions of the citric acid cycle are oxidative decarboxylations? How are they alike, and how are they different?
6. How does α-ketoglutarate resemble pyruvate, and how does α-ketoglutarate dehydrogenase resemble PDH?
7. What is the overall reaction catalyzed by pyruvate dehydrogenase (PDH)? What is the order in which substrates are bound and in which products are released?
8. What coenzymes are required by each of the three enzymes (E1, E2, and E3) in PDH, and what does each do in the reaction?
9. What are the enzymes of the citric acid cycle? For each, what is the structure of the substrate(s), and what reaction occurs? What is the structure of each product?
10. What high energy coenzymes are produced in the citric acid cycle, and what reaction produces each?
11. What are the intermediates in the reactions catalyzed by citrate synthase, aconitase, and succinyl-CoA synthetase?
12. Which reactions of the citric acid cycle involve oxidation to produce a double bond, hydration of the double bond, and oxidation? How are the two oxidations different?

Electron Transport

1. Where does electron transport occur, and why is that important?
2. What enzymes catalyze the reactions of electron transport? How is proton transport related to electron transport, and how is it different?
3. Given the reduction potentials of the molecules involved, how can you write a balanced redox reaction and calculate ΔE°' and ΔG°' for the reaction? How do you know whether or not the reaction is spontaneous?
4. What molecules, in what order, are required to move 2 e- from NADH to O2? To move 2 e- from succinate to O2?
5. How is pH related to ΔGT for the inner mitochondrial membrane?
6. What are the characteristics of the inner mitochondrial membrane?
7. What are cytochromes? How do they differ from each other, and how are they alike?
8. How many electrons are involved in an oxidation-reduction reaction that includes NADH, or Q, or cytochromes, or O2?
9. For each complex involved in electron transport, what is oxidized, what is reduced, and how many H+ are moved from N to P for each reaction?
10. What equation relates ΔE°' and ΔG°'?
11. What are uncouplers, and why are they important?

Oxidative Phosphorylation and Shuttles

1. What process provides the energy for ATP synthesis by ATP synthase? How is that process related to electron transport?
2. How does Fo move protons across the membrane?
3. How are the conformation changes of F1 (in ATP synthase) related to the function of Fo?
4. What determines the stoichiometry of ATP synthesis? What is the relationship between NADH oxidation and ATP synthesis, and why doesn't it have to be a whole-number relationship? What is the relationship between QH 2 oxidation and ATP synthesis?
5. Why are shuttles required for recycling NADH produced in glycolysis? How are they related to your answers to question 4?
6. What type of regulation is used for oxidative phosphorylation?
7. What are the important subunits of Fo in ATP synthase? What does each do in order to move H+ across the membrane?
8. What are the important subunits of F1 in ATP synthase? What does each do?
9. What are the conformations of the β subunits, and what are their characteristics?
10. What carrier moves protons across the membrane P → N, and what other molecule is moved at the same time? What other carriers are required for ATP synthesis? What carriers and enzymes are required for NADH shuttles? Which carriers are antiports, and which are symports?
11. What is the net number of ATP synthesized per glucose degraded to CO2? How does that number change when cell type changes?
12. What are the important molecules that are involved in regulation of oxidative phosphorylation?

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