Examination 5: Chapters 29 through 33

This exam combines questions from exams given during past years. The correct answer, relative objective, and percent of the class answering each question correctly is at the end of the examination. The mean score for the entire exam is also listed.

1. The enzyme phosphofructokinase-2/fructose-2,6-bisphosphatase plays a key role in the control of glycolysis exerted by the insulin to glucagon ratio. If the insulin to glucagon ratio increases, phosphofructokinase-2/fructose-2,6-bisphosphatase would:
  1. Become more phosphorylated and phosphofructokinase-2 would become more active
  2. Become less phosphorylated and phosphofructokinase-2 would become less active
  3. Become more phosphorylated and phosphofructokinase-2 would become more active
  4. Become less phosphorylated and phosphofructokinase-2 would become more active
  5. Become less phosphorylated and fructose-2,6-bisphosphatase would become more active
2. During a fast, the liver enzyme pyruvate kinase becomes:
  1. More active and more phosphorylated
  2. More active and less phosphorylated
  3. Less active and more phosphorylated
  4. Less active and less phosphorylated
3. This patient has been taking dexamethasone for severe asthma for several weeks. She has developed hyperglycemia and muscle weakness. A partial explanation of these symptoms might be:
  1. The inhibition of net muscle protein catabolism
  2. A decreased concentration of blood amino acids
  3. Induction of phosphoenolpyruvate carboxykinase
  4. An inhibition of fructose-1,6-bisphosphatase
  5. Increased secretion of insulin
4. The pentose phosphate pathway can, without help from glycolysis or gluconeogenesis, perform the following EXCEPT:
  1. The synthesis of NADPH from glucose-6-phosphate
  2. The synthesis of ribose-5-phosphate from glucose-6-phosphate
  3. The synthesis of ribose-5-phosphate from fructose-6-phosphate and glyceraldehyde-3-phosphate
  4. The synthesis of glucose-6-phosphate from ribose-5-phosphate
  5. The synthesis of fructose-6-phosphate and glyceraldehyde-3-phosphate from ribose-5-phosphate
5. Which of the following would NOT require NADPH?
  1. The reduction of antioxidant vitamins
  2. Detoxification reactions that use P450
  3. The reductive biosynthesis of cholesterol
  4. The biosynthesis of palmitate
  5. The beta-oxidation of fatty acids
6. A patient takes sulfa drugs for the first time and develops hemolytic anemia. The other blood cells appear normal. The best explanation is:
  1. The red blood cells have more active glucose-6-phosphate dehydrogenase
  2. The red blood cells have more glutathione reductase activity
  3. The red blood cells have more NADH in their cytosol
  4. The other cells have more active glucose-6-phosphate dehydrogenase activity
  5. The other cells have higher NADPH concentrations
7. After ingestion of a high carbohydrate meal, all of the following are true EXCEPT:
  1. Glucose transport into muscle and adipose tissue is increased
  2. Glucose uptake and utilization by adipose tissue is increased
  3. Glucose storage in glycogen is increased
  4. Glycolysis in the liver is increased
  5. Glucose uptake by the brain is increased
8. When glucagon binds to a liver cell,
  1. G-protein binds to ATP
  2. Adenylate cyclase is activated
  3. Protein phosphatase is activated
  4. Cyclic-AMP is decreased
  5. The configuration of every protein mentioned above is changed
9. After a 24 hour fast, the maintenance of blood glucose is largely a result of the change in the insulin to glucagon ratio. All of the following help to explain this mechanism EXCEPT:
  1. More free fatty acid is mobilized from adipose tissue
  2. More glycerol is mobilized from adipose tissue
  3. More acetyl CoA is produced from free fatty acid in the liver
  4. Acetyl CoA activates pyruvate carboxylase
  5. Oxaloacetate is used as the principal source of energy to drive gluconeogenesis
10. Bob was brought to the emergency room. His wife said that he was a 33 year old and had IDDM. He had told her last night that he had forgotten whether he had taken his injection. Since he couldn't remember, he gave himself another injection. His blood glucose was 25 mg/dL. At the present time and compared to a normal person, Bob has:
  1. High blood fatty acids
  2. Low blood ketone bodies
  3. High gluconeogenesis
  4. High concentration of protein kinase A in adipose cells
  5. High cyclic-AMP levels in adipose cells
11. Which of the following enzymes is NOT part of the pathway for converting carbon atoms in glucose to carbon atoms in free fatty acids in the liver?
  1. Pyruvate dehydrogenase
  2. Pyruvate carboxylase
  3. Citrate synthase
  4. Citrate lyase
  5. Alpha-ketoglutarate dehydrogenase
12. All of the following are intermediates in the synthesis of triacylglycerol from glucose following a high carbohydrate meal EXCEPT:
  1. Dihydroxyacetone phosphate
  2. Glycerol phosphate
  3. Monoacylglycerol
  4. Phosphatidic acid
  5. Diacylglycerol
13. Ginny has been fasting (500 kcal/day) for several days. All of the following would be increased EXCEPT:
  1. Cyclic-AMP in adipose tissue
  2. The activity of hormone sensitive lipase in adipose tissue
  3. The concentration of glycerol phosphate in adipose tissue
  4. The amount of free fatty acid bound to albumin in the blood
  5. The amount of free fatty acid entering the liver mitochondria
14. Phosphatidylethanolamine is converted to phosphatidylcholine in an enzyme reaction that transfers three activated methyl groups to the ethanolamine converting it to phosphatidylcholine. This reaction requires the cofactor:
  1. Biotin
  2. Thiamine pyrophosphate
  3. S-adenosylmethionine
  4. Vitamin B12
  5. Methylene tetrahydrofolate
15. Which of the following is NOT a glycerophospholipid commonly found in cell membranes:
  1. Phosphatidylglycine
  2. Phosphatidylcholine
  3. Phosphatidylserine
  4. Phosphatidylethanolamine
  5. Phosphatidylinositolbisphosphate
16. You are a fourth year medical student on rounds in the pediatric unit. The patient is a premature infant with respiratory distress syndrome. The attending physician asks the students present to explain the molecular cause of the disease. Student 1 says that the infant is not making enough dipalmitoylphosphatidylcholine. Student 2 says that the infant is not able to make enough lecithin. Student 3 says that the infant is not able to make enough sphingomyelin. Your best answer is:
  1. Students 1, 2, and 3 are all correct
  2. Students 1 and 2 are both correct and student 3 is incorrect
  3. Student 2 is correct and students 1 and 3 are both incorrect
  4. Students 1,2,and 3 are all incorrect
  5. Student 3 is correct and students 1 and 2 are both incorrect
17.

During gluconeogenesis, an increased concentration of acetyl-CoA in the liver cell will activate:
  1. Mitochondrial pyruvate carboxylase
  2. Mitochondrial phosphoenolpyruvate carboxykinase
  3. Cytosolic phosphoenolpyruvate carboxykinase
  4. Cytosolic pyruvate carboxylase
  5. Cytosolic pyruvate kinase
18.

When pyruvate carboxylase and phosphoenolpyruvate carboxykinase are active, futile cycling is prevented by:
  1. Phosphorylation and activation of pyruvate kinase by insulin via cAMP
  2. Dephosphorylation and inactivation of protein kinase by glucagon via cAMP
  3. Phosphorylation and activation of protein kinase by insulin via cAMP
  4. Phosphorylation and inactivation of pyruvate kinase by glucagon via cAMP
19.

Gluconeogenesis ends with the conversion of fructose-1,6-bisphosphate to glucose in a series of three enzymatic steps. Which of the following statements regarding these enzymes is TRUE:
  1. All three of these enzymes release inorganic phosphate and two are also used in the reverse reaction in glycolysis
  2. Two of these enzymes release inorganic phosphate and the other is also used in the reverse reaction in glycolysis
  3. Two of these enzymes release inorganic phosphate, and two are also used in the reverse reaction in glycolysis
  4. One of these enzymes releases inorganic phosphate, and the other two are also used in the reverse reactions in glycolysis
  5. One of these enzymes releases inorganic phosphate, and all three enzymes are used in the reverse reactions in glycolysis
20.

An increase in the insulin/glucagon ratio would lead to______________ and a(n) __________conversion of phosphoenolpyruvate to pyruvate.
  1. The dephosphorylation of pyruvate kinase and an increase in the
  2. The phosphorylation of pyruvate kinase and an increase in the
  3. The phosphorylation of pyruvate kinase and an decrease in the
  4. The dephosphorylation of pyruvate kinase and an decrease in the
21.

The hexose monophosphate shunt is:
  1. Found mostly in the mitochondria of muscle cells
  2. Found mostly in the cytosol of cells that rely heavily upon anaerobic glycolysis
  3. Found mostly in the cytosol of cells that do not rely upon vitamin C or vitamin D for protection against free radicals
  4. Found in the mitochondria of all cells
  5. Found in the cytosol of all cells
22.

If a cell needed to make exactly twice the amount of NADPH as ribose-5-phosphate, which glycolytic substrate(s) would be most efficient:
  1. Glucose-6-phosphate and fructose-1,6-bisphosphate
  2. Fructose-6-phosphate and dihydroxyacetone phosphate
  3. Glucose-6-phosphate
  4. Fructose-6-phosphate and glyceraldehyde-3-phosphate
  5. Glucose-6-phosphate and dihydroxyacetone phosphate
23.

Glutathione is continuously being reduced and oxidized. Which group on the molecule is actually being reduced and oxidized:
  1. The hydroxyl group of threonine
  2. The sulfhydryl group of cysteine
  3. The carboxyl group of aspartate
  4. The reactive hydrogen of histidine
  5. The amide group of asparagine
24.

A pathway exists that uses substrate(s) from the glycolytic pathway to produce reducing agents that remove H2O2 from the cell. Al of the following enzymes are used by that pathway EXCEPT:
  1. 6-phosphogluconate dehydrogenase
  2. Glucose-6-phosphate dehydrogenase
  3. Cytochrome P450 monooxygenase
  4. Glutathione reductase
  5. Glutathione peroxidase
25.

A person fasts for 12 hours and then eats a high protein meal. About 45 minutes later their blood is analyzed. Compared to blood levels before ingestion:
  1. Insulin will be higher. Glucagon will be higher. Liver glycolysis will be active.
  2. Insulin will be higher. Glucagon will be higher. Liver gluconeogenesis will be active.
  3. Insulin will be lower. Glucagon will be higher. Liver glycolysis will be active.
  4. Insulin will be lower. Glucagon will be higher. Liver gluconeogenesis will be active.
  5. Insulin will be higher. Glucagon will be lower. Liver gluconeogenesis will be active.
26.

Regarding dietary glucose entering the liver following a high caloric, high carbohydrate meal. Which of the following statements is NOT true:
  1. Some glucose is converted to glycerol phosphate
  2. Some glucose is stored as glycogen
  3. Some glucose is used via aerobic glycolysis
  4. Some glucose is used via anaerobic glycolysis
  5. Some glucose is used for fatty acid synthesis
27.

When going from the fed state to the fasted state, the activity of the glycolytic and gluconeogenic pathways are changed. Part of the mechanism for this change is:
  1. An increase in the activity of 3',5'-phosphosdiesterase
  2. An increase in the activity of phosphofructokinase-2
  3. An increase in the activity of fructose-2,6-bisphosphatase
  4. A decrease in the activity of protein kinase
  5. A decrease in the ativity of adenylate cyclase
28.

You meet your patient in the emergency room. She forgot that she took her first shot of insulin last night and so she took a second shot. She is now in a hypoglycemic coma. Which of the following is contributing tho the low blood sugar:
  1. Insulin has activated the cyclic AMP cascade in the liver
  2. Insulin has activated the cyclic AMP cascade in adipose tissue
  3. Insulin has caused an increase in ketone bodies synthesis in the liver
  4. Insulin has inhibited fructose-1,6-biphosphatase in the liver
  5. Insulin has inhibited glucose uptake and released across the liver cell membrane
29.

Both acetyl CoA and the acyl carrier protein
  1. Transfer one carbon units
  2. React only with each other
  3. Only react when vitamin B12 is present
  4. Are synthesized from vitamin thiamine
  5. Contain phosphopantetheine reactive groups
30.

Which of the following is NOT an intermediate in the synthesis of triaclglycerol from glucose-6-phosphate and fatty acids in adipose tisssue:
  1. Glycerol
  2. Dihydroxyacetone phosphate (DHAP)
  3. Phosphatidic acid
  4. Diacylglycerol
  5. Acyl-CoA

ANSWERS

Correct answers and percentage of the class answering correctly. As a reference point, last year's class scored a combined mean of 71.6% for questions 1 through 30.

1: D, 70%. Chapter 31, Objective 22: " As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with gluconeogenesis and glycolysis so that glucose is released into the blood. From the time when glucagon binds it's receptor, be able to name all the intermediates in the proper order in the pathway that activates fructose-1,6-bisphosphatase and inhibits phosphofructokinase-1 and pyruvate kinase. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphofructokinase-2/fructose-2,6-bisphosphatase, and fructose-2,6-bisphosphate."

2: C, 90%. Chapter 31, Objectives 10 and 22: "Explain the control of the conversion of pyruvate to phosphoenolpyruvate during gluconeogenesis. Name two enzymes in the pathway, a positive allosteric modifier activates one and one is activated principally by induction. Why isn't phosphoenolpyruvate converted to pyruvate and why isn't pyruvate converted to acetyl CoA during gluconeogenesis? Include the terms acetyl CoA, cyclic-AMP, phosphorylation, NADH, and, again, acetyl CoA in your answer." " As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with gluconeogenesis and glycolysis so that glucose is released into the blood. From the time when glucagon binds it's receptor, be able to name all the intermediates in the proper order in the pathway that activates fructose-1,6-bisphosphatase and inhibits phosphofructokinase-1 and pyruvate kinase. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphofructokinase-2/fructose-2,6-bisphosphatase, and fructose-2,6-bisphosphate."

3: C, 64%. Chapter 31, Objective 28: "Concerning Emma Wheezer: What were the effects of dexamethasone that contributed to muscle weakness and hyperglycemia?"

4: D, 59%. Chapter 29, Objective 2: "If a cell needs both NADPH and ribose-5-phosphate, what substrates from glycolysis are used by the pentose phosphate pathway to make them? If a cell needs only ribose-5-phosphate what substrates from glycolysis are used by the pentose phosphate pathway?"

5: E, 84%. Chapter 29, Objective 3: "What is NADPH used for?"

6: D or E, 85%. Chapter 29, Objective 5: "Concerning Al Martini: This patient has glucose-6-phosphate dehydrogenase deficiency. Why are red blood cells lysed while other cells of the body remain intact? Why didn't this disease show up earlier in life?"

7: E, 56%. Chapter 31, Objective 11: "How does the insulin/glucagon ratio stimulate the storage of triacylglycerol in adipose tissue following a high carbohydrate meal?"

8: B, 89%. Chapter 31, Objective 21: "As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with glycogen metabolism so that glucose is released into the blood. Be able to name all the intermediates in the proper order in this pathway. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphorylase kinase, phosphorylase, glycogen synthase, glucose-1-P, glucose-6-P, glucose-6-phosphatase, and glucose."

9: E, 71%. Chapter 31, Objective 10: " Explain the control of the conversion of pyruvate to phosphoenolpyruvate during gluconeogenesis. Name two enzymes in the pathway, a positive allosteric modifier activates one and one is activated principally by induction. Why isn't phosphoenolpyruvate converted to pyruvate and why isn't pyruvate converted to acetyl CoA during gluconeogenesis? Include the terms acetyl CoA, cyclic-AMP, phosphorylation, NADH, and, again, acetyl CoA in your answer."

10: B, 65%. Chapter 31, Objective 30: "Concerning Di Abietes, who suffers from Type I diabetes and is in a coma because she took an overdose of insulin 13 hours ago, (1) how can you tell from her rate and depth of respiration that she is not suffering from diabetic ketoacidosis? (2) what had happened to the normal pathways for energy production in the fasting state? Include fatty acid mobilization, ketone body synthesis, glycogenolysis, and gluconeogenesis.

11: E, 59%. Chapter 33, Objective 1: "What is the pathway for the conversion of glucose to acetyl CoA in the cytosol in preparation for fatty acid synthesis?"

12: C, 61%. Chapter 33, Objective 9. " Starting with an intermediate in glycolysis and acyl CoA, be able to name the intermediates in the synthesis of triacylglycerols in liver and adipose tissue."

13: C, 75%. Chapter 33, Objective 12: "Be able to list the sequence of events from the time epinephrine binds a receptor on the surface of an adipose cell until acetyl CoA is made in muscle or liver. Don't forget the key enzyme that controls the process."

14: C, 75%. Chapter 33, Objective 16: "In the synthesis of membrane lipids, what is the function of SAM?"

15: A, 83%. Chapter 33, Objective #13. "Be able to name 4 glycerophospholipids found in cell membranes."

16: B, 32%. Chapter 33, Objective #19. "Concerning Colleen Lakker: What was the major cause of respiratory distress syndrome of this premature infant? What are the two compounds in the amniotic fluid analyzed before birth of a premature infant? Are they both derivatives of phosphatidic acid?"

17: A, 75%. Chapter 31, Objective 7. " Describe the pathway for the conversion of pyruvate to phosphoenolpyruvate by naming the intermediates, the compartments, the control enzyme, and the allosteric regulator for the control enzyme. Include the terms pyruvate carboxylase, biotin, ATP, oxaloacetate, acetyl CoA, malate dehydrogenase, NADH, malate, phosphoenolpyruvate carboxykinase, GTP. Ignore aspartate."

18: D, 98%. Chapter 31, Objective 22: " As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with gluconeogenesis and glycolysis so that glucose is released into the blood. From the time when glucagon binds it's receptor, be able to name all the intermediates in the proper order in the pathway that activates fructose-1,6-bisphosphatase and inhibits phosphofructokinase-1 and pyruvate kinase. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphofructokinase-2/fructose-2,6-bisphosphatase, and fructose-2,6-bisphosphate."

19: B, 88%. Chapter 31, Objective 8. " Name the phosphatases that convert fructose-1,6-bisphosphate to glucose in liver."

20: A, 87%. Chapter 31, Objective 22: " As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with gluconeogenesis and glycolysis so that glucose is released into the blood. From the time when glucagon binds it's receptor, be able to name all the intermediates in the proper order in the pathway that activates fructose-1,6-bisphosphatase and inhibits phosphofructokinase-1 and pyruvate kinase. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphofructokinase-2/fructose-2,6-bisphosphatase, and fructose-2,6-bisphosphate."

21: E, 73%. Chapter 29, Objective 1. Describe the pentose phosphate pathway: Names: Functions: Substrates: Products: Control Enzymes: Regulation: Compartment(s): Tissues of interest:

22: C, 81%. Chapter 29, Objective 2. " If a cell needs both NADPH and ribose-5-phosphate, what substrates from glycolysis are used by the pentose phosphate pathway to make them? If a cell needs only ribose-5-phosphate what substrates from glycolysis are used by the pentose phosphate pathway?"

23: B, 58%. Chapter 29, Objective 4. " Assume that you have a patient that has hemolytic anemia a result of eating fava beans. Name the deficient enzyme and the other enzymes in the pathway that leads to the reduction of HOOH."

24: C, 54%. Chapter 29, Objective 4. " Assume that you have a patient that has hemolytic anemia a result of eating fava beans. Name the deficient enzyme and the other enzymes in the pathway that leads to the reduction of HOOH."

25: B, 39%. Chapter 31, Objective 16. " What happens to the blood concentrations of insulin and glucagon and the insulin/glucagon ratio following ingestion of a high carbohydrate meal, a high protein meal, and a normal meal?"

26: D, 54%. Chapter 31, Objective 17. "What is the fate of glucose in the liver following a normal or high carbohydrate meal? How does the increased blood glucose and the increased insulin/glucagon ratio affect the cAMP cascade, the activity of protein phosphatase, glycogen synthesis, glycogenolysis, glycolysis, gluconeogenesis, glycerol-3-phosphate synthesis, fatty acid synthesis, triacylglycerol synthesis, and VLDL synthesis?"

27: C, 86%. Chapter 31, Objective 22. " As blood glucose decreases and the insulin to glucagon ratio drops, the cyclic AMP cascade causes a change in the activities of the enzymes concerned with gluconeogenesis and glycolysis so that glucose is released into the blood. From the time when glucagon binds it's receptor, be able to name all the intermediates in the proper order in the pathway that activates fructose-1,6-bisphosphatase and inhibits phosphofructokinase-1 and pyruvate kinase. Use the terms glucagon receptor, G-protein, adenyl cyclase, cAMP, protein kinase A, regulatory subunits, catalytic subunits, phosphofructokinase-2/fructose-2,6-bisphosphatase, and fructose-2,6-bisphosphate."

28: D, 91%. Chapter 31, Objective 30: "Concerning Di Abietes, who suffers from Type I diabetes and is in a coma because she took an overdose of insulin 13 hours ago, (1) how can you tell from her rate and depth of respiration that she is not suffering from diabetic ketoacidosis? (2) what had happened to the normal pathways for energy production in the fasting state? Include fatty acid mobilization, ketone body synthesis, glycogenolysis, and gluconeogenesis."

29: E, 88%. Chapter 33, Objective 4. " What do acyl carrier protein and CoA have in common?"

30: A, 58%. Chapter 33, Objective 9. " Starting with an intermediate in glycolysis and acyl CoA, be able to name the intermediates in the synthesis of triacylglycerols in liver and adipose tissue."

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