Questions:

1. Following a high protein meal, amino acids might be used for the synthesis of all of the following EXCEPT
  1. Proteins
  2. Essential nitrogen compounds like neurotransmitters
  3. Thiamine pyrophosphate
  4. Glucose
  5. Fatty acids
2. All of the following occur when muscle protein is catabolized during a fast EXCEPT
  1. Some of the amino acids are oxidized in the muscle to produce energy
  2. Most of the amino acids, including large amounts of glutamine and alanine are released from muscle cells
  3. Most of the nitrogen atoms are incorporated into uric acid
  4. Gluconeogenesis uses some of the amino acids as substrates
  5. Some amino acids are catabolized to acetyl CoA that is used for energy
3. All of the following are true for the enzyme abbreviated AST EXCEPT
  1. Is sometimes called aspartate aminotransferase
  2. Can produce glutamate if NADPH and α-ketoglutarate are substrates
  3. Can produce α-ketoglutarate and aspartate
  4. Can produce glutamate and oxaloacetate
  5. The Keq = 1
4. All of the following are true for the enzyme abbreviated ALT EXCEPT
  1. It is sometimes called alanine aminotransferase
  2. It catalyzes a reversible reaction
  3. Can produce pyruvate and glutamate
  4. Can produce alanine and α-ketoglutarate
  5. Can produce NH4+, if the substrate is glutamate
5. Concerning ALT, AST and all other transamination reactions, all of the following are true EXCEPT
  1. The cofactor may be called pyridoxal phosphate (PLP)
  2. The cofactor is derived from pyridoxine or vitamin B6
  3. Pyridoxal phosphate is called a prosthetic group because it is held tightly to enzymes
  4. Pyridoxamine is an intermediate in the reaction
  5. These enzymes are classified as oxidoreductases
6. If the pH of a solution is 7.3 and the pKa for ammonium ion is 9.3, then the ratio of  [NH3]/[NH4+] would be
  1. 100/1
  2. 10/1
  3. 2/1
  4. 1/10
  5. 1/100
7. All of the following are major sources of free ammonia in the liver, muscle and other tissues EXCEPT
  1. The glutamic acid dehydrogenase reaction
  2. Most transamination reactions
  3. The deamination of amino acids
  4. Glutaminase and asparaginase reactions
  5. The urease reaction in the gut
8. All of the following are true for the glutamate dehydrogenase reaction EXCEPT

  1. Its substrates can be aspartate + H2O + NAD+
  2. Its substrates can be α-ketoglutarate + NADH + NH4+ +H+
  3. It adds NH4+ to the solution when the concentration of NH4+ is low
  4. It removes NH4+ from the solution when the concentration of NH4+ is high
  5. It is an anaplerotic reaction for the TCA cycle
9. All of the following statements about the synthesis of nonessential amino acids are true EXCEPT

  1. The carbon structure can usually be made from glucose
  2. The carbon structure can usually be made from fatty acids
  3. The amino group can be transferred from glutamate
  4. The amino group can originate from free ammonium ion if glutamate dehydrogenase and a transaminase are used
  5. The amino group can originate from alanine if two transaminase reactions are used
10. When urea is synthesized in the liver, all of the following may be occurring EXCEPT
  1. Glutamate may be synthesized from α-ketoglutarate using a number of amino transferase reactions
  2. Aspartate may be synthesized from oxaloacetate and glutamate using AST
  3. Many amino acids may transfer their amino groups directly to oxaloacetate to form aspartate
  4. Glutamate may be synthesized using the glutamate dehydrogenase reaction if ammonium ion is in excess
  5. Glutamate may be providing free ammonium ion if the concentration of free ammonium ion is low
11. If a portion of the brain is producing a lot of ammonium ions, all of the following may occur EXCEPT
  1. Using gluconeogenesis, the brain could produce α-ketoglutarate
  2. α-ketoglutarate could react with NH4+ + NADH + H+ to form glutamate using glutamate dehydrogenase
  3. Glutamate could react with ATP + NH4+ to form glutamine using the enzyme glutamine synthetase
  4. Glutamine could travel to the liver where glutaminase could hydrolyze the amide nitrogen producing free NH4+ for urea synthesis
  5. In the liver, glutamate could undergo gluconeogenesis after transferring its α-amino group to oxaloacetic acid
12. Even though one of them is not in the cycle, all of the following are important enzymes of the urea cycle EXCEPT
  1. Carbamoylphosphate synthetase II in the cytosol
  2. Ornithine transcarbamylase in the mitochondria
  3. Argininosuccinate synthetase in the cytosol
  4. Argininosuccinate lyase in the cytosol
  5. Arginase in the cytosol
13. The control enzyme of the urea cycle is ___________ and it is regulated by ________________

  1. Arginase:    allosteric inhibition by urea
  2. Argininosuccinase lyase:  allosteric inhibition by fumarate
  3. Argininosuccinate synthetase:  allosteric inhibition by AMP
  4. Ornithine transcarbamoylase:  allosteric activation by citrulline
  5. Carbamoyl phosphate synthetase-1:  allosteric activation by N-acetylglutamate
14. During the progression of a prolonged fast, all of the following are true EXCEPT
  1. Muscle protein is broken down to provide amino acids, which are a major substrate for gluconeogenesis
  2. The nitrogen atoms from the amino acids that are converted to glucose or used for energy must be eliminated as urea
  3. More fatty acids are converted to ketone bodies
  4. The brain uses a constant amount of energy that it gets from either glucose or ketone bodies
  5. More brain energy supplied by ketone bodies means less brain energy has to be supplied from amino acids and more urea has to be made
15. This patient has a deficiency of argininosuccinate lyase and has very high concentrations of blood glutamine and ammonium ion.  You could treat her with all of the following EXCEPT
  1. Low protein diet
  2. Arginine supplementation to her diet
  3. Oral doses of hippuric acid and phenylacetylglutamine
  4. Benzoic acid tablets
  5. Oral doses of pheylbutyrate
16. Your patient, Percy Veere, has hepatitis A so you order a set (panel) of liver functions tests.  You will expect all of the following changes in the serum concentrations and reasons for the changes to be correct EXCEPT

  1. Aspartate aminotransferase (AST) will rise dramatically because of leakage from damaged or dead liver cells
  2. Alanine aminotransferase (ALT) will rise dramatically because of leakage from damaged or dead liver cells
  3. Total bilirubin will rise dramatically because of increased red blood cell lysis
  4. Alkaline phosphatase, normally tethered to the bile canaliculi, will be freed and find its way back to the blood
17. Your patient, Percy Veere, has hepatitis A and an excess of ammonium ions.  Some of those ammonium ions are generated in his brain.  The normal mechanism for detoxifying ammonium ions in the brain includes all of the following EXCEPT

  1. α-ketoglutarate from the TCA cycle plus ammonium ion plus NADH form glutamate
  2. The enzyme converting α-ketoglutarate to glutamate is glutamate dehydrogenase
  3. Glutamate plus ATP plus ammonium ion form glutamine
  4. The enzyme is glutamine synthetase
  5. Glutamine is normally excreted in the urine at even low concentrations
18. Your patient, Percy Veere, has hepatitis A that results in high serum ammonium ion and glutamine concentrations.  Which of the following treatments might help? Select the best answer.
  1. A lower protein diet would decrease nitrogen uptake and lower the ammonium ion and glutamine being formed
  2. Antibiotics would stop the growth of bacteria in the gut.  This would lower the urease concentration of the gut and the amount of free ammonium ion formed from urea
  3. Lactulose was developed as an osmotic laxative and flushes bacteria from the gut, lowering the production of ammonium from urea
  4. All of the above are valid treatments and might help
19. All of the following occur when muscle protein is catabolized during a fast EXCEPT
  1. Some of the carbon skeletons are used for energy in the muscle following transamination
  2. The nitrogen of some amino acids is transferred to pyruvate and forms glutamine for export to the liver
  3. The nitrogen of some amino acids ends up as the amide nitrogen of glutamine before export to other tissues
  4. Some of the nitrogen ends up as ammonium in the urine
  5. Most of the nitrogen ends up in urea synthesized in the liver
20. Alanine can provide both amino groups for urea synthesis. All of the following reactions would be used EXCEPT
  1. Alanine + α-ketoglutarate = pyruvate + glutamate
  2. Glutamate + oxaloacetate = aspartate + α-ketoglutarate
  3. Glutamate + NAD+ = NADH + H+ + NH4+ + α-ketoglutarate
  4. HCO3- + NH4+ + 2ATP = carbamoyl phosphate + 2 ADP+ 2Pi
  5. Aspartate + Ornithine + ATP = Argininosuccinate + AMP + PPi
21. Starting with the ornithine transcarbamoylase reaction, the order in which intermediates in the urea cycle would occur is
  1. citrulline, argininosuccinate, arginine, ornithine
  2. argininosuccinate, citrulline, arginine, ornithine
  3. argininosuccinate, arginine, citrulline, ornithine
  4. citrulline, arginine, argininosuccinate, ornithine
  5. citrulline, arginine, ornithine, argininosuccinate
22. Starting with free ammonium ion and the carbamoyl phosphate synthetase reaction,
  1. carbamoyl phosphate is synthesized in the cytosol
  2. the nitrogen from aspartate is added to citrulline in the mitochondria
  3. arginase produces urea in the mitochondria
  4. ornithine is converted to citrulline in the mitochondria
  5. fumarate is produced from argininosuccinate in the mitochondria

Answers:

1. Answer: C. Chapter 38, Objective 1: When more amino acids are ingested than are needed to replace protein and other nitrogenous compounds, what is their fate? Back to question 1.
2. Answer: C. Chapter 38, Objective 2: When muscle protein is catabolized in muscle during a fast, what are the fates of the amino acids? Back to question 2.
3. Answer: B. Chapter 38, Objectives 3 and 4: What is another name for transamination reactions? Be able to write a reaction for AST, ALT, or any other transamination reaction. What is the approximate Keq for these reactions? Back to question 3.
4. Answer: E. Chapter 38, Objectives 3 and 4: What is another name for transamination reactions? Be able to write a reaction for AST, ALT, or any other transamination reaction. What is the approximate Keq for these reactions? Back to question 4.
5. Answer: E. Chapter 38, Objective 5: What are the cofactors for ALT and AST. Are the coenzymes prosthetic groups? What vitamin are the cofactors derived from? Back to question 5.
6. Answer: E. 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. Back to question 6.
7. Answer: B. Chapter 38, Objective 7: What are the major sources of free ammonia in the liver, muscle and other tissues? Back to question 7.
8. Answer: A. Chapter 38, Objective 8: Be able to write the glutamate dehydrogenase reaction. Is this reaction readily reversible? Back to question 8.
9. Answer: B. Chapter 38, Objective 9: Glutamate is important in the synthesis of nonessential amino acids. How does glutamate acquire the amino groups for this purpose? Back to question 9.
10. Answer: C. Chapter 38, Objective 10: 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? Back to question 10.
11. Answer: A. Chapter 38, Objective 11: When excess NH4+ is produced in most cells of the body, it can be combined with glutamate and transported to the liver where it is released as free NH4+. Name the two enzymes and the intermediate in this process. Back to question 11.
12. Answer: A. Chapter 38, Objective 12: Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved? Back to question 12.
13. Answer: E. Chapter 38, Objective 13: How is the urea cycle regulated? Back to question 13.
14. Answer: E. Chapter 38, Objective 14: How is the production of urea during a fast related to the need for blood glucose and the catabolism of muscle protein? How does the production of ketone bodies fit in? Back to question 14.
15. Answer: C. Chapter 38, Objective 15: Name 3 ways to treat argininosuccinate lyase deficiency and explain their rationale. Back to question 15.
16. Answer: C. Chapter 38, Objective 16: Concerning Percy Veere who has hepatitis A: What liver function tests were ordered? Why was the serum concentration of each substance increased? Back to question 16.
17. Answer: E. Chapter 38, Objective 17: Concerning Percy Veere who has hepatitis A: Name the enzymes and intermediates in the conversion of ammonium ion and a-ketoglutarate to glutamine in the brain. Back to question 17.
18. Answer: D. 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? Back to question 18.
19. Answer: B. Chapter 38, Objective 2: When muscle protein is catabolized in muscle during a fast, what are the fates of the amino acids? Back to question 19.
20. Answer: E. Chapter 38, Objective 10 and 12: 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? Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved? Back to question 20.
21. Answer: A. Chapter 38, Objective 12: Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved? Back to question 21.
22. Answer: D. Chapter 38, Objective 12: Know the substrates, products, and five enzymes of the urea cycle. Which compartments are involved? What tissues are involved? Back to question 22.