Examination 6: Chapters 36 through 39

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. During fasting, all of the following would tend to increase the flux through gluconeogenesis EXCEPT:
  1. The concentration of free amino acids increases
  2. The concentration of glycerol increases
  3. The concentration of cyclic-AMP rises
  4. The concentration of fructose-2,6-bisphosphate rises
  5. The enzyme phosphoenolpyruvate carboxykinase is induced
2. All of the following contribute to the increase in ketone body synthesis in the liver during fasting EXCEPT:
  1. The increased insulin to glucagon ratio activates lipoprotein lipase in adipose tissue
  2. Increased blood concentrations of free fatty acids bound to albumin
  3. Inactive acetyl CoA carboxylase
  4. More flux through beta-oxidation
  5. The liver makes more acetyl CoA than the TCA cycle can use
3. A patient with type I diabetes has come to the emergency room with ketoacidosis. All of the following might help to explain why her ketones are high EXCEPT:
  1. Protein kinase A in her liver is to high
  2. Free fatty acids in her blood are two high
  3. Too much acetyl-CoA is produced by the liver
  4. Too much hydroxymethylglutaryl CoA is produced
  5. Carnitine deficiency
4. The pKa for ammonium ion is about 9.4 and the pH of blood is about 7.4. The ratio of ammonia to ammonium ion (ammonia/ammonium ion) in blood is about:
  1. 1/100
  2. 1/10
  3. 0
  4. 10/1
  5. 100/1
5. Which of the following enzyme reactions takes place during the synthesis of urea from ammonium ion and glutamate?
  1. Carbamoyl phosphate + citrulline = ornithine
  2. Aspartate + citrulline + ATP = argininosuccinate + AMP + PPi
  3. Argininosuccinate = aspartate + arginine
  4. CO2 + NH4+ + 2 ADP = carbamoyl phosphate + 2 ATP
  5. Argininosuccinate = arginine + urea
6. All of the following would be expected to increase the activity of the urea cycle EXCEPT:
  1. Antibiotics
  2. Switching to a high protein diet
  3. Going from the fed state of a normal diet to a fasting state
  4. An increase in gluconeogenesis
  5. Stress
7. Which of the following is an essential amino acid?
  1. Alanine
  2. Glycine
  3. Valine
  4. Aspartate
  5. Serine
8. The products of the catabolism of cysteine are:
  1. Serine and phosphate
  2. Serine and HCl
  3. Pyruvate and sulfate
  4. Serine and sulfate
  5. Alanine and sulfate
9. All of the following are substrates or products of the phenylalanine hydroxylase reaction EXCEPT:
  1. Tetrahydrofolate
  2. H20
  3. Dihydrobiopterin
  4. Tyrosine
  5. O2
10. You suspect that your 12 year old male patient has an inborn error in methionine metabolism. It may be that cystathionine synthase is deficient. If this is true, he should have high serum concentrations of:
  1. Methionine
  2. Cysteine
  3. Cystathionine
  4. Alpha-ketobutyrate
  5. Methyl cobalamin
11. As a result of having the disease phenylketonuria, phenyl ketones are found in the urine. The best explanation for this is:
  1. Tyrosine hydroxylase is absent and lactate dehydrogenase is absent
  2. Phenylalanine hydroxylase is absent and aminotransferases are absent
  3. Tyrosine hydroxylase is present and lactate dehydrogenase is present
  4. Phenylalanine hydroxylase is present and tyrosine hydroxylase is absent
  5. Phenylalanine hydroxylase is absent and aminotransferases are present
12. Following a meal, glucose will be stored in liver glycogen because:
  1. Hexokinase will be phosphorylated as a result of the high insulin to glucagon ratio
  2. Hexokinase will be dephosphorylated following a reduction in protein kinase A
  3. Glycogen phosphorylase A will be inactivated by phosphorylation by protein kinase A
  4. Phosphorylase kinase will be inactivated by phosphorylation by protein kinase A
  5. Glycogen synthase will be activated by protein phosphatase
13. The enzyme acetyl CoA carboxylase is activated following an increase in:
  1. Malonyl CoA
  2. Protein kinase A activity
  3. Cyclic AMP
  4. Palmitoyl CoA
  5. Proteins phosphatase activity
14. The delivery of free fatty acids from lipoproteins into adipose tissue cells will be increased by:
  1. Epinephrine
  2. Norepinephrine
  3. Diabetes
  4. Glucagon
  5. Insulin
15. Compared to a normal person, a patient with diabetes Type II:
  1. Will release more insulin from her beta cells following the same meal
  2. Will produce less glucose via gluconeogenesis during a fast
  3. Will have adipose tissue cells that are just as responsive to insulin
  4. Will have muscle cells that are just as responsive to insulin
  5. Will synthesize more lipoprotein in the fasting state
16. During a fast, muscle protein is catabolized to free amino acids. All of the following scenarios occur EXCEPT:
  1. Alanine travels to the liver and is used for gluconeogenesis
  2. Alanine travels to the liver and donates an amino group to the synthesis of urea
  3. Glutamine travels to the kidney where it's amide group is used to buffer the urine
  4. Alanine is used for gluconeogenesis in the muscle
  5. Most amino acids travel to the liver and are used by the liver for gluconeogenesis
17. Which of the following statements about glutamate is NOT true:
  1. It can be synthesized in the transaminase reaction using alanine as a substrate
  2. It can be synthesized in an aminotransferase reaction using aspartate as a substrate
  3. It can be synthesized by the glutamate dehydrogenase reaction using alpha-ketoglutarate and free ammonium ion as substrates
  4. It can transfer it's amino group to oxaloacetate in a one step reaction
  5. It can transfer it's amino group to citrulline in a one step reaction
18. The urea cycle is regulated by:
  1. Acetyl CoA
  2. Citrate
  3. Malonyl CoA
  4. N-acetylglutamate
  5. Cytoplasmic carbamoyl phosphate
19. The carbon structure of this amino acid can be converted in a single enzyme step into an interemediate in either the TCA cycle or the urea cycle:
  1. Arginine
  2. Citrulline
  3. Aspartate
  4. Glutamate
  5. Glutamine
20. Which of the following is an essential amino acid:
  1. Alanine
  2. Serine
  3. Tryptophan
  4. Glutamine
  5. Asparagine
21. Serine is a nonessential amino acid. The precursor in glycolysis or the TCA cycle from which serine is made is:
  1. Glutamate
  2. Oxaloacetate
  3. Pyruvate
  4. 3-phosphoglycerate
  5. Methionine
22. All of the following amino acids are glucogenic EXCEPT:
  1. Leucine
  2. Alanine
  3. Glutamate
  4. Phenylalanine
  5. Cystine

 ANSWERS

Correct answers and percentage of the class answering correctly. As a reference point, last year's class scored a combined mean of 81.5% for questions 1 through 22.

1: D, 55%. Chapter 36, Objective 14: "Glycolysis dose not function when gluconeogenesis is functioning. What factors turn on gluconeogenesis and turn off glycolysis?"

2: A, 93%. Chapter 36, Objective 16: "Why are ketone bodies produced during fasting?"

3: E, 85%. Chapter 36, Objective 21. " Concerning Ann Sulin who has type II diabetes: On a molecular level, explain why she has high serum triacylglycerol. Why does she have high blood glucose? Would you expect ketoacidosis?"

4: A, 88%. Chapter 38, Objective 6. Around pH = 7.3, which is the most prevalent form, ammonia or ammonium ion? Use the pKa = 9.3 and the Henderson Hasselbalch Equation to prove it.

5: B, 86%. Chapter 38, Objective 12:" Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved?"

6: A, 80%. Chapter 38, Objective 18. Concerning Percy Veere who has hepatitis A: Why would a low protein diet, antibiotics, enemas and lactulose lower his blood ammonium ion level?

7: C, 98%. Chapter 39, Objective 1: "What is an essential amino acid? Which ones are they?"

8: C, 79%. Chapter 39, Objective 8: "What are the products of the catabolism of cysteine?"

9: A, 68%. Chapter 39, Objectives 11 and 12. Be able to state the components of the reaction that converts phenylalanine to tyrosine. What are the molecular causes of phenylketonuria? Why is phenylketonuria not called phenylalanineuria? How are ketones formed?

10: A, 92%. Chapter 39, Objective 13: "Concerning Homer Sistine...If he had an inborn error in cystathionine synthase, what would happen to his concentrations of methionine, homocysteine, and cysteine? Why? If his problem had been a deficiency of folate or vitamin B12 , what would you expect to happen to the concentrations of methionine, homocysteine, and cysteine? Why?"

11: E, 81%. Chapter 39. Objectives 11 and 12. Be able to state the components of the reaction that converts phenylalanine to tyrosine. What are the molecular causes of phenylketonuria? Why is phenylketonuria not called phenylalanineuria? How are ketones formed?

12: E, 82%. Chapter 36, Objective 1. Describe the pathway for the storage of glucose in the liver in the fed state? How is this pathway regulated? Are there any possible futile cycles prevented?

13: E, 65%. Chapter 36, Objective 5. Which enzyme controls the pathway for the synthesis of fatty acids from acetyl CoA in the cytosol? How is this pathway regulated? (ignore citrate)

14: E, 99%. Chapter 36, Objective 9. How does insulin affect the delivery of free fatty acid into adipose cells in the fed state?

15: E, 50%. Chapter 36, Objective 21. Concerning Ann Sulin who has type II diabetes: On a molecular level, explain why she has high serum triacylglycerol. Why does she have high blood glucose? Would you expect ketoacidosis?

16: D, 65%. Chapter 38 Objective 2. When muscle protein is catabolized in muscle during a fast, what are the fates of the amino acids?

17: E, 88%. Chapter 38, Objectives 9 and 10. Glutamate is important in the synthesis of nonessential amino acids. How does glutamate acquire the amino groups for this purpose? Glutamate is important in the synthesis of urea. How does glutamate acquire the amino groups for this purpose? What does glutamate do with the amino groups?

18: D, 92%. Chapter 38, Objective 13. How is the urea cycle regulated?

19: C, 73%. Chapter 38, Objectives 7 and 12. What are the major sources of free ammonia in the liver, muscle and other tissues? Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved?

20: C, 95%. Chapter 39. Objective 1. What is an essential amino acid? Which ones are they?

21: D, 85%. Chapter 39. Objective 2. State the metabolites from which each nonessential amino acid is synthesized. These metabolites are found in glycolysis or the TCA cycle. One metabolite is an essential amino acid.

22: A, 95%. Chapter 39. Objectives 3 and 5. What is a glucogenic amino acid? Which pathways do their catabolic products enter? For each amino acid, be able to say where its catabolic products enter the TCA cycle, the glycolytic/gluconeogenic pathways, or the ketone body pathway.

gyonuschot@une.edu