Questions:

1. An essential amino acid is one that you cannot make at a rate consistent with normal growth and maintenance.  Which of the following sets consist only of essential amino acids?
  1. Alanine, tyrosine, cystine
  2. Leucine, lysine, tryptophane
  3. Alanine, glutamate, aspartate
  4. Glutamate, proline, glycine
  5. Glutamine, asparagine, tyrosine
2. All of the following choices have an nonessential amino acid and a metabolite from which it can be made EXCEPT
  1. Serine from 3-phosphoglycerate in glycolysis
  2. Alanine from pyruvate in glycolysis
  3. Methionine from pyruvate in glycolysis
  4. Glutamate from α-ketoglutarate in the TCA cycle
  5. Tyrosine from phenylalanine
3. Which of the following statements concerning gluconeogenesis from amino acids is FALSE 

  1. A gluconeogenic amino acid can be a substrate for gluconeogenesis
  2. Leucine is a substrate for gluconeogenesis
  3. Aspartate is a gluconeogenic amino acid
  4. Phenylalanine is a substrate for gluconeogenesis
  5. Tryptophane is a substrate for gluconeogenesis
4. Which of the following statements concerning ketogenic amino acids is FALSE
  1. They have carbon skeletons that can serve as precursors of ketone bodies
  2. Lysine is a ketogenic amino acid
  3. Glutamate is a ketogenic amino acid
  4. Leucine is a ketogenic amino acid
  5. Tryptophane is a ketogenic amino acid
5. Each of the following groups of amino acids enters the TCA cycle as indicated EXCEPT
  1. Arginine, histidine, glutamine, and proline enter at α-ketoglutarate
  2. Lysine and leucine enter at isocitrate
  3. Valine, isoleucine and methionine enter at succinyl CoA
  4. Tyrosine and phenylalanine enter at fumarate
  5. Aspartate and asparagine enter at oxaloacetate
6. Concerning the cofactor tetrahydrofolate, all of the following are true EXCEPT
  1. Folic acid is a vitamin
  2. Tetrahydrofolate is cofactor made from folic acid
  3. Tetrahydrofolate is a cofactor for only two known enzyme reactions in humans
  4. Tetrahydrofolate removes a one-carbon unit from serine as serine is changed to glycine
  5. N5,N10-methylene tetrahydrofolate will probably transfer its one carbon unit to some other metabolite
7. Concerning the biological conversion of serine to cysteine, all of the following are true EXCEPT 

  1. Homocysteine derived from methionine is necessary for the conversion
  2. The enzyme cystathionine synthase converts homocysteine and serine into cystathionine
  3. The enzyme cystathionase converts cystathionine to ammonium ion, α-ketobutyrate, and cysteine
  4. Because cysteine has to be synthesized from methionine and serine, it is an essential amino acid
  5. The product α-ketobutyrate can be used for gluconeogenesis
8. Concerning the metabolism of cysteine, all of the following are true EXCEPT
  1. During catabolism, the sulfhydryl group is oxidized and eventually becomes hydrogen sulfate
  2. Proteins are considered acidic because their catabolism produces H2SO4
  3. The carbon skeleton of cysteine was derived from methionine
  4. The carbon skeleton of cysteine is catabolized to pyruvate
  5. The amino group of cysteine was transferred to α-ketoglutarate and can be eliminated as urea
9. Much of the carbon skeleton of methionine is readily catabolized to all of the following EXCEPT
  1. Propionyl CoA
  2. Succinyl CoA
  3. Fumarate
  4. Oxaloacetate
  5. Hydroxymethylglutaryl CoA
10. Arginine is
  1. An essential amino acid in adults and children
  2. An essential amino acid in adults but not children
  3. An essential amino acid in children but not adults
  4. A nonessential amino acid in children and adults
  5. A nonessential amino acid in children
11. Concerning the catabolism of phenylalanine, all of the following are true EXCEPT
  1. Phenylalanine is converted to the nonessential amino acid tyrosine by the enzyme phenylalanine hydroxylase
  2. The enzyme is sometimes called a mixed function oxidase because both tetrahydrobiopterin and phenylalanine are oxidized by O2
  3. The tetrahydrobiopterin produced by the phenylalanine hydroxylase reaction must be reduced back to dihydrobiopterin by the enzyme dihydrobiopterin reductase
  4. Some forms of disease phenylketoneurea are due to defects in enzymes that synthesize tetrahydrobiopterin from GTP
  5. Some forms of disease phenylketoneurea are due to a deficiency in dihydrobiopterin reductase
12. Concerning classic phenylketoneurea, all of the following are true EXCEPT
  1. At birth, the patient's phenylalanine levels are very high because the mother’s liver will not catabolize phenylalanine
  2. These patients have hyperphenylalaninemia
  3. Phenylalanine at very high concentrations is converted to phenylpyruvate (phenylketone) by a transamination reaction
  4. These patients have high phenylpyruvate (phenylketone) in the urine
  5. The original smelly compounds found in urine were phenylketones and were used to name the disease
13. Your patient has a high serum homocysteine level and a defect in the enzyme that transfers one-carbon units from N5-methyltetrahydrofolate to form methylcobalamin (B12).  The greatest change from normal would be in the rate of conversion of
  1. Methionine to homocysteine
  2. Homocysteine to methionine
  3. Homocysteine to succinyl CoA
  4. Serine to cysteine
  5. Cysteine to pyruvate and H2SO4
14. An essential amino acid is one that you cannot make at a rate consistent with normal growth and maintenance. Which of the following sets consist only of essential amino acids?
  1. Tryptophane, histidine, phenylalanine
  2. Tryptophane, tyrosine, histidine
  3. Lysine, leucine, serine
  4. Methionine, tryptophane, cysteine
  5. Threonine, serine, alanine
15. All of the nonessential amino acids are synthesized from glycolysis, the TCA cycle, or an essential amino acid. Which of the following pairs in NOT CORRECT?
  1. Serine from 3-phosphoglycerate in glycolysis
  2. Alanine from pyruvate in glycolysis
  3. Aspartate from oxaloacetate in the TCA cycle
  4. Glutamine from a-keto glutarate in the TCA cycle
  5. Phenylalanine from the essential amino acid tyrosine
16. All of the nonessential amino acids are synthesized from glycolysis, the TCA cycle, or an essential amino acid. Which of the following pairs in NOT CORRECT?
  1. Cystine from oxaloacetate in the TCA cycle
  2. Glutamine from a-keto glutarate in the TCA cycle
  3. Asparagine from oxaloacetate in the TCA cycle
  4. Proline from a-keto glutarate in the TCA cycle
  5. Arginine from a-keto glutarate in the TCA cycle
17. All of the following pairs are at least partially glucogenic EXCEPT
  1. Lysine and leucine
  2. Lysine and serine
  3. Leucine and aspartate
  4. Phenylalanine and tyrosine
  5. Aspartate and glutamate
18. At least a portion of the carbon skeleton a ketogenic amino acid must be catabolized to at least one of the following EXCEPT
  1. Succinyl CoA
  2. Acetyl CoA
  3. Acetoacetyl CoA
  4. Acetoacetate
  5. Hydroxymethylglutaryl CoA
19. The carbon skeleton of all of the following amino acids are catabolized to pyruvate or 2-phosphoglycerate EXCEPT
  1. Serine
  2. Cysteine
  3. alanine
  4. Glycine
  5. Arginine
20. The carbon skeleton of all of the following amino acids are catabolized to intermediates in the Tricarboxylic Acid Cycle EXCEPT
  1. Methionine
  2. Aspartate
  3. Glutamate
  4. Valine
  5. Lysine
21. Your patient has high levels of methionine and homocysteine and low levels of cysteine. Which of the following enzymes are probably missing or defective?
  1. α-ketobutyrate dehydrogenase
  2. Cystathionine synthase
  3. Methionine adenosyltransferase
  4. Phosphatidylethanolamine N-methyltransferase
  5. Dihydrofolate reductase

Answers:

1. Answer: B. Chapter 39, Objective 1: What is an essential amino acid? Which ones are they? Back to question 1.
2. Answer: C. 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. Back to question 2.
3. Answer: B. Chapter 39, Objective 3: What is a glucogenic amino acid? Which pathways do their catabolic products enter? Back to question 3.
4. Answer: C. Chapter 39, Objective 4: What is a ketogenic amino acid? What are their catabolic products that are ketone bodies or intermediates in the pathway for ketone body synthesis? Back to question 4.
5. Answer: B. Chapter 39, Objective 5: 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. Back to question 5.
6. Answer: C. Chapter 39, Objective 6: Name the cofactor produced from folic acid. What is the function of this cofactor? Describe the reaction in which serine and glycine are interconverted. Back to question 6.
7. Answer: D. Chapter 39, Objective 7: Name the reactants and products of each reaction in the conversion of serine to cysteine. Back to question 7.
8. Answer: C. Chapter 39, Objective 8: What are the products of the catabolism of cysteine? Back to question 8.
9. Answer: E. Chapter 39, Objective 9: What is the product of methionine degradation that is also a metabolite in the TCA cycle? Back to question 9.
10. Answer: C. Chapter 39, Objective 10: When does arginine become an essential amino acid? When is arginine not an essential amino acid? Back to question 10.
11. Answer: C. Chapter 39, Objective 11: Be able to state the components of the reaction that converts phenylalanine to tyrosine. What are the molecular causes of phenylketonuria? Back to question 11.
12. Answer: A. Chapter 39, Objective 12: Why is phenylketonuria not called phenylalanineuria? How are ketones formed? Back to question 12.
13. Answer: B. 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? Back to question 13.
14. Answer: A. Chapter 39, Objective 1: What is an essential amino acid? Which ones are they? Back to question 14.
15. Answer: E. 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. Back to question 15.
16. Answer: A. 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. Back to question 16.
17. Answer: A. Chapter 39, Objective 4: What is a ketogenic amino acid? What are their catabolic products that are ketone bodies or intermediates in the pathway for ketone body synthesis? Back to question 17.
18. Answer: A. Chapter 39, Objective 4: What is a ketogenic amino acid? What are their catabolic products that are ketone bodies or intermediates in the pathway for ketone body synthesis? Back to question 18.
19. Answer: E. Chapter 39, Objective 5: 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. Back to question 19.
20. Answer: E. Chapter 39, Objective 5: 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. Back to question 20.
21. Answer: B. 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? Back to question 21.