320 Exam 4 Practice Questions FA23

docx

School

University of Massachusetts, Amherst *

*We aren’t endorsed by this school

Course

320

Subject

Chemistry

Date

Jan 9, 2024

Type

docx

Pages

Uploaded by BaronBadger2687

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst BIOCHEM 320 Exam 4 Practice Questions Short Answer 1. Draw the structure of the fatty acid 12:2 Δ5,8 . 2. Explain why glucose produces less energy per carbon than a fatty acid. 3. If you were going on an extensive trip through the wilderness, would it be better to build up your glycogen stores or your triacylglycerol stores? Why? 4. Does fatty acid oxidation of a fatty acid designated 16:1 Δ6 yield more, fewer or the same number of ATP as a fatty acid designated 16:0? Why? 5. Explain the relationship between fatty acid oxidation and β-oxidation. 6. Here is the first reaction of β-oxidation. Which molecule is oxidized and which molecule is reduced? Is the overall ΔE°’ positive or negative? (Note: Please refer to the Reduction Potential Table on the Exam Reference Sheet to find E°’ for FAD. The E°’ for trans-Δ2-enoyl- CoA → acyl-CoA is ~ - 0.67 V.) Acyl-CoA + FAD → trans-Δ2-enoyl-CoA + FADH 2 7. What are the products from β-oxidation of a fatty acid designated 14:0? How many rounds of the β- oxidation cycle are required? 8. Compare and contrast fatty acid oxidation and fatty acid synthesis. Write down all the ways the processes are similar and all the ways they are different. 9. Explain why the ultimate source of all the carbons in the fatty acid chains synthesized in your cells is acetyl-CoA. 10. Arachidonic acid (20:4 Δ5,8,11,14 ) is a fatty acid that is particularly abundant as a component of phospholipids in the membranes of your muscle, liver, and brain cells. Can arachidonic acid be produced “from scratch” in your cells? Explain your answer. 11. Thinking about the process of fatty acid synthesis, explain why the vast majority of fatty acids have an even number of carbons. 12. Use the information on the Exam 4 Reference sheet to calculate the net amount of ATPs that can be produced from an 8-carbon fatty acid (8:0). 13. Using your metabolic pathway diagram as a reference, explain how glucose (sugar) can be converted to a fatty acid (lipid). 14. What determines whether a reaction is classified as reversible or irreversible? Why are enzymes that catalyze irreversible reactions key regulatory enzymes? 15. Only a small amount of hormone is necessary to generate a significant response in a cell. Explain how this is possible and why it is beneficial. 16. Draw a flowchart to illustrate how low blood sugar affects gluconeogenesis. Include all the steps we discussed. 17. Thinking about the fact that glucagon signaling leads to activation of a kinase, while insulin signaling results in the activation of a phosphatase, what does that tell you about the phosphorylation state of metabolic enzymes in response to glucagon signaling? insulin signaling? 18. Thinking about insulin effects, explain why it makes sense that the hormone produces an increase in glycogen synthesis, but a decrease in glycogen degradation. In other words, what advantage exists because of the way the hormone controls opposing pathways? 1

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst 19. If a mutation occurred in glycogen synthase so that the enzyme was no longer able to function in a cell, would this mutation affect glycogen synthase activity under conditions of low blood glucose? If so, how? If not, why not? 20. Describe how the levels of F-2,6-BP alter the activity of PFK-1 and fructose-1,6-bisphosphatase. 21. Which pathway, glycolysis or gluconeogenesis, is more active when levels of fructose-2,6-BP are low? Explain your answer. 22. High levels of ATP and NADH (high energy state) decrease the rates of acetyl-CoA formation and the citric acid cycle reactions. Why does this regulation “make sense”? 23. Draw a flowchart or use words to explain how the hormones glucagon and insulin affect the activity of acetyl-CoA carboxylase (ACC). Indicate in your explanation (image) whether signaling of the hormone leads to phosphorylation or dephosphorylation of ACC. 24. Fill out this table that summarizes the effects of insulin and glucagon on metabolic pathways in liver and skeletal muscle cells. In each box, indicate whether insulin (glucagon) increases, decreases or has no effect on the rate of the metabolic pathway. Multiple Choice 1. Which of the following statements about ketogenesis is/are TRUE? A. An overabundance of acetyl-CoA can lead to the production of ketone bodies. B. Ketone bodies are important metabolic fuel for liver cells. C. Some animal cells take up ketone bodies and convert them back to acetyl-CoA. D. A and B, but not C are true statements. E. A and C, but not B are true statements. F. B and C, but not A are true statements. 2. When calculating the ATP yield for a fatty acid, which of the following steps is/are involved? I. Multiplying the total number of FADH 2 by 2.5 II. Subtracting 2 ATP needed for the energy investment phase of β-oxidation III. Determining the total number of acetyl-CoA produced from acyl-CoA A. I only 2

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst B. II only C. III only D. I and II only E. I and III only F. II and III only 3. _____ acetyl-CoA are produced by β-oxidation of a fatty acid designated 12:0. A. Twelve B. Ten C. Six D. Five 4. The defining feature of lipids is that they are significantly nonpolar, and most are mainly composed of hydrogen and carbon. Therefore, _____ are the most important interactions for the properties of a lipid. A. hydrogen bonds B. dispersion forces C. ionic bonds D. hydrogen bonds and dispersion forces E. hydrogen bonds, dispersion forces, and ionic bonds 5. Acetyl-CoA carboxylase (ACC) catalyzes the formation of malonyl-CoA used in the synthesis of fatty acids. Action of a phosphatase “turns on” ACC activity. It is reasonable to predict that signaling leads to of ACC by the phosphatase. A. glucagon; phosphorylation B. insulin; phosphorylation C. glucagon; dephosphorylation D. insulin; dephosphorylation 6. Which of the following pathways, if any, can occur in muscle cells but NOT liver cells? A. glycolysis B. gluconeogenesis C. acetyl-CoA formation D. citric acid cycle E. None of the above is unique to muscle cells. 7. When carbon monoxide is added to an actively respiring muscle cell that is using fatty acids for fuel, which of the following predicts the effect of carbon monoxide on the rate of oxygen usage and the rate of proton flow through ATP synthase? A. The rate of oxygen usage remains the same, but the rate of proton flow through ATP synthase decreases. 3

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst B. The rate of proton flow through ATP synthase remains the same, but the rate of oxygen usage decreases. C. The rates of both oxygen usage and proton flow through ATP synthase decrease. D. The rates of both oxygen usage and proton flow through ATP synthase remain the same. 8. Unsaturated fatty acids yield _______ energy than saturated fatty acids due to the presence of double bonds that make unsaturated fatty acids ______ oxidized. A. more; less B. more; more C. less; less D. less; more 9. Which set of electron carriers would produce the most ATP? A. 4 NADH, 2 FADH 2 B. 4 NAD + , 2 FADH C. 2 NADH, 4 FADH 2 D. 2 NAD + , 4 FADH 10. How is fatty acid synthesis similar to fatty acid oxidation? A. Both occur completely in the mitochondria. B. Both add/remove 2-carbon units. C. Both use a single enzyme with multiple functions. D. All of the above describe similarities. 11. After what step in fatty acid oxidation are the carbons of a fatty acid completely oxidized? A. acyl-CoA formation B. carnitine acyl-CoA transport C. β - oxidation D. citric acid cycle E. oxidative phosphorylation 12. What is the relationship between acyl-CoA and acetyl-CoA? A. acetyl-CoA is a type of acyl-CoA B. acyl-CoA is a type of acetyl-CoA C. acyl-CoA and acetyl-CoA are different names for the same molecule 13. Rate of flux through which of the following biochemical pathways would be increased in response to glucagon in a liver cell? A. fatty acid synthesis 4

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst B. gluconeogenesis C. glycogen synthesis D. A and B, but not C E. B and C, but not A 14. Glucagon and insulin signaling regulate breakdown and synthesis of glycogen. It is reasonable to predict that glucagon signaling will ________ glycogen breakdown to release glucose and ______ glycogen synthesis. A. activate; activate B. inhibit; activate C. activate; inhibit D. inhibit; inhibit 15. Rate of flux through which of the following biochemical pathways, if any, would be increased in response to insulin in a liver cell? A. gluconeogenesis B. glycogen synthesis C. Both A and B. D. None of the above. 16. F-2,6-BP is an allosteric effector of PFK-1 in glycolysis and F-1,6-BPase in gluconeogenesis. Which of the following is a/are reasonable prediction(s) about F-2,6-BP? A. F-2,6-BP binds to a location on PFK-1 or F-1,6-BPase that is not the active site. B. F-2,6-BP levels are controlled by insulin and glucagon. C. A high level of F-2,6-BP will have opposite effects on enzymes in glycolysis and gluconeogenesis. D. All of the above are reasonable predictions. 17. The graph to the right illustrates PFK-1 (glycolysis enzyme) activity. When a liver cell responds to glucagon, the levels of F-2,6-BP will be ______ , leading to a affinity of PFK-1 for its substrate. A. low; weak B. low; strong C. high; weak D. high; strong 18. Use the graph of PFK-1 activity (glycolysis enzyme) from the previous question to answer this question. When blood glucose levels are high, would you predict the change in the level of F-2,6-BP in liver cells of a type 2 diabetic would be the SAME, HIGHER, or LOWER when compared to a non-diabetic? A. SAME B. HIGHER C. LOWER 5

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst 19. In a cell, which of the following do you predict is a shared characteristic of all regulated reactions in glycolysis and gluconeogenesis? A. The reactions are all redox reactions. B. The reactions all form ATP from ADP and Pi. C. In all reactions, K is much larger than Q. D. All reactions are reversible. 20. Why does it make sense that the production of malonyl-CoA during fatty acid synthesis inhibits the carnitine acyl-CoA transport system? A. Because the cell needs to make sure it has enough substrate to produce malonyl-CoA. B. Because the cell needs to make sure the fatty acids being synthesized are not immediately oxidized. C. Because the cell needs to make sure the acyl-CoA produced remains in the mitochondrial matrix. D. All of the above are equally valid answers. 21. When a liver cell responds to insulin, which pair of pathways both increase in activity to facilitate creation of fatty acids? A. Gluconeogenesis and citric acid cycle B. Glycolysis and citric acid cycle C. Gluconeogenesis and fatty acid synthesis D. Glycolysis and fatty acid synthesis 22. Why can fatty acids store more energy than glycogen? A. Fat molecules are hydrophobic which allows them to pack more molecules into a smaller space. B. Fatty acids are more oxidized and have many carbon oxygen bonds compared to glucose. C. Fatty acids have hydrophilic characteristics. D. The non-polar character of fatty acids means they can be transported easily. 23. If a fatty acid containing 18 carbons participates in β-oxidation, how many cycles are required, and what are the products? A. 7 cycles produce 8 Acetyl-CoA, 7 NADH, 7 FADH2 B. 8 cycles produce 9 Acetyl-CoA, 9 NADH, 9 FADH2 C. 8 cycles produce 9 Acetyl-CoA, 8 NADH, 8 FADH2 D. 9 cycles produce 8 Acetyl-CoA, 8 NADH, 8 FADH2 24. The concentration of ATP ([ATP]) can affect PFK-1. What happens to PFK-1 when we have high [ATP] in the cell? A. PFK-1 is inhibited; therefore, gluconeogenesis is inhibited. 6

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst B. PFK-1 is activated; therefore, gluconeogenesis is inhibited. C. PFK-1 is activated; therefore, glycolysis is inhibited. D. PFK-1 is inhibited; therefore, glycolysis is inhibited. 25. Which statement about skeletal muscle cells, if any, is correct? A. Glucagon will increase fatty acid oxidation. B. Muscle cells store triglycerides to meet their own energy needs. C. The rate of glycogen breakdown is slower than synthesis by 300-fold. D. None of the above. 26. Refer to the graph to the right. PFK-1 has a _______ affinity for substrate when [F-2,6-BP] is _____________. A. strong; low B. strong, high C. weak, high D. weak; low E. More than one answer is correct. 27. Select the regulatory enzyme of the fatty acid synthesis pathway that is correctly matched with its corresponding function. A. Acetyl-coA Carboxylase; Ligation of a bicarbonate ion and acetyl-coA to create malonyl-CoA B. Acetyl-coA Carboxylase; Ligation of oxaloacetate and acetyl-coA to create citrate C. Fatty Acid Synthase; Covalent attachment of acetyl group to palmitate D. Fatty Acid Synthase; Elongation and desaturation of fatty acids 28. Liver has evolved to produce ketone bodies for other body cells. Which of the following options, if any, represents a strategy to regulate this process? A. liver lacks enzymes for ketone body degradation B. liver lacks enzymes for ketone body synthesis C. liver uses feed-forward regulation to reduce levels of ketone body precursors D. None of the above is a strategy. 29. Regulation of glycogen synthesis and degradation in skeletal muscle cells prevents a futile cycle A. by simultaneously activating glycogen synthase and glycogen phosphorylase. B. by simultaneously inactivating glycogen synthase while activating glycogen phosphorylase. C. when activated glycogen synthase binds to glycogen phosphorylase, leading to inhibition of phosphorylase activity. D. when increasing concentrations of glucose molecules allosterically activate glycogen phosphorylase but allosterically inhibit glycogen synthase. 7

© 2023 – Becky M. Miller and Elizabeth B. Mearls for Biochemistry 320 at UMass Amherst 30. Which of the following is a true statement about hormonal regulation of pyruvate kinase (PK), the enzyme that catalyzes glycolysis reaction #10? A. Dephosphorylation by glucagon signaling inhibits PK activity. B. Phosphorylation by glucagon signaling inhibits PK activity. C. Direct allosteric inhibition by glucagon inhibits PK activity. D. Direct allosteric activation by glucagon activates PK activity. 31.What is the physiological role of an uncoupler protein? A. It allows cells to use fatty acids for energy when glucose is in limited supply. B. It allows cells to generate heat by blocking proton pumping in the electron transport chain. C. It allows cells to generate heat by oxidizing fatty acids without producing ATP. D. It allows cells to decrease their rates of cellular respiration when the organism is at rest. E. It allows cells to increase their rates of cellular respiration when ATP is in high demand. 8

320 Exam 4 Practice Questions FA23

Related Documents