Questions:

1. Catalytic power could be defined as the

  1. Rate of the enzyme catalyzed reaction divided by the rate of the uncatalyzed reaction
  2. Rate of the enzyme uncatalyzed reaction divided by the rate of the catalyzed reaction
  3. Ability to distinguish an enzyme substrate from a group of very similar compounds
  4. Ability to distinguish an enzyme product from a group of very similar compounds
  5. Ability to hold the substrate very tightly to the active site
2. The enzyme with a high specificity would be one that

  1. Catalyzed a reaction at a rate much faster than the rate of the uncatalyzed reaction
  2. Would accept only carbohydrates as substrates
  3. Would accept only cytoplasmic substrates
  4. Usually produced 4 products in the mitochondria
  5. Used only glucose as a substrate
3. Which of the following statements is NOT true?  The active site is a region

  1. On or near the surface of an enzyme
  2. That binds the substrate
  3. With unchanging conformation
  4. Where bonds are formed between the substrate and the R-groups of the protein
  5. Where the transition state complex is formed
4. The difference between the Induced Fit Theory Model for Substrate Binding and the Lock-and-Key Model for Substrate Binding involved

  1. The complementarity of charge
  2. The complementarity of topology
  3. The separation of R-groups along the polypeptide chains
  4. The induction of conformational change
  5. The formation of a transition state complex
5. An enzyme has catalytic power because it’s transition state

  1. Lowers the energy level of the substrates
  2. Requires less activation energy
  3. Lowers the energy level of the products
  4. Has less energy than the substrates
  5. Allows less substrate molecules to achieve the transition state
6. Which of the following statements are FALSE?

  1. All vitamins are cofactors
  2. All coenzymes are cofactors
  3. Some metal ions are cofactors
  4. Some metal ions are prosthetic groups
  5. Some coenzymes are prosthetic groups
7. An activation-transfer coenzyme usually does all of the following EXCEPT

  1. Forms a covalent bond with a substrate molecule
  2. Forms a bond that contains a lot of energy
  3. Does not bind to the enzyme
  4. Binds to the substrate
  5. Activates the substrate for transfer
8. Thiamine pyrophosphate

  1. Is synthesized from the vitamin pantothenate (pantothenic acid)
  2. Reacts with glucose
  3. Forms only ionic bonds with substrates
  4. Binds to the carboxyl group of pyruvate
  5. Binds to the alpha-keto group of alpha-ketoglutarate
9. Coenzyme A
  1. Is derived from thiamine
  2. Has a functional group containing cobalt
  3. Forms thioester bonds with substrates
  4. Has a sulfhydryl functional group that reacts only with amino groups
  5. Activates alcohol groups
10. All of the following are true about biotin EXCEPT?  Biotin
  1. Is a coenzyme
  2. Usually removes CO2 from substrates
  3. Is a cofactor for carboxylase enzymes
  4. Is a prosthetic group
  5. Forms covalent bonds with CO2
11. All of the following are true, EXCEPT?  Pyridoxal phosphate
  1. Is an activation-transfer coenzyme
  2. Is also called vitamin B12
  3. Often transfers amino groups
  4. Binds to the enzyme
  5. Forms a covalent bond with the substrate
12. All of the following statements about NAD+ are true, EXCEPT?  NAD+
  1. Is synthesized from the vitamin niacin
  2. Is a cofactor to many dehydrogenase enzymes
  3. Accepts hydride ions and becomes NADH when oxidizing substrates
  4. Contains an ADP group that binds to the enzyme
  5. Can be used to reduce pyruvate to lactate
13. A plot of activity versus pH for an enzyme that functions in the cytosol of a cell at pH of about 7 would probably

  1. Look about the same as an enzyme like pepsin that functions in the stomach at a pH of about 1
  2. Show the highest activity between pH of 4 and 6
  3. Show the lowest activity at pH of about 7 to 8
  4. Show the same activity at every pH between 4 and 10
  5. Have the highest activity around a pH of 7
14. When the activity of a human enzyme is plotted versus temperature in degrees centigrade, the activity will usually

  1. Decrease from 20 to 30 degrees
  2. Increase from 0 to 45 degrees and then decrease suddenly
  3. Increase from 0 to 100 degrees and then decrease suddenly
  4. Stay the same between 0 and 100 degrees and then decrease suddenly
  5. Slowly decrease between 20 and 40 degrees and then decrease suddenly
15. Concerning the reaction between diisopropylphosphofluoridate and acetylcholine esterase, you would expect
  1. Diisopropylphosphofluoridate to be bound loosely (reversibly) at the active site
  2. A decrease in muscle activity
  3. An increase in the hydrolysis of acetylcholine
  4. A decrease in the activity of acetylcholine esterase
  5. Covalent bonds to form between diisopropylphosphofluoridate and acetylcholine
16. All of the following are true for aspirin, EXCEPT?  Aspirin
  1. Is acetylsalicylic acid (acetylsalicylate)
  2. Is an irreversible inhibitor of prostaglandin endoperoxide synthase (cyclooxygenase)
  3. Transfers an acetyl group to a seryl group at the active site
  4. Resembles the normal substrate for prostaglandin endoperoxide synthase (cyclooxygenase)
  5. Binds to the active site of prostaglandin endoperoxide synthase (cyclooxygenase) after the acetyl group has been hydrolyzed
17. All of the following are true about penicillin binding to glycopeptidyl transferase, EXCEPT.  Penicillin binds tightly

because it
  1. resembles the shape and charge of the normal activated complex
  2. is a suicide inhibitor
  3. contains the dipeptide bond between two L-alanine residues
  4. is a transition state analog
  5. reacts to form a covalent bond with the enzyme
18. Xanthine oxidase (xanthine dehydrogenase) is an enzyme that does all of the following EXCEPT:
  1. helps catabolize pyrimidine bases
  2. Reacts irreversibly with allopurinol
  3. Uses hypoxanthine as a substrate
  4. Uses xanthine as a substrate
  5. Produces uric acid as a product
19. Most of the Xanthine oxidase (xanthine dehydrogenase) is found in
  1. the urine.
  2. the intercellular fluid
  3. only kidney cells
  4. the intracellular fluid
  5. urate crystals
20. In general, heavy metals are toxic because they all (pick the best answer)
  1. form covalent bonds with enzymes
  2. react with active sites
  3. precipitate and denature enzymes
  4. change the normal conformation of proteins
  5. replace calcium as a cofactor on key enzymes
21. Aldolase is classified as a
  1. Oxidoreductase
  2. Transferase
  3. Hydrolase
  4. Lyase
  5. Isomerase
22. The difference between a synthase and a synthetase is that, in the case of the synthetase, the new covalent bond that is formed is always linked to the

  1. Formation of water
  2. Reduction of NAD+
  3. Hydrolysis of ATP
  4. Transfer of a phosphate group
  5. Isomerization of one of the substrates
23. Concerning Dennis "the menace" Veere, who swallowed an overdose of the insecticide Malathion.  Malathion was converted to malaoxon in the liver and distributed to the tissues where it caused the symptoms because
  1. It binds reversibly to the acetylcholine receptor
  2. It binds but will not react with the active site of acetylcholine esterase
  3. It causes the hydrolysis of too much acetylcholine
  4. It formes a salt bound with the active site of acetylcholine esterase
  5. It binds and causes an increase in the acetylcholine concentration
24. Concerning your patient Lotta Topaigne, Allopurinol is used to treat her gout because it
  1. Is a reversible inhibitor of xanthine oxidase (xanthine dehydrogenase)
  2. Increases the conversion of xanthine to urate
  3. Reduces the conversion of hypoxanthine to urate
  4. Inhibits xanthine oxidase (xanthine dehydrogenase) without binding to the active site
  5. Converts urate to uric acid
25. Concerning Al Martini who is an alcoholic, his enzyme, alcohol dehydrogenase,
  1. Uses thiamine pyrophosphate as a cofactor
  2. Produces acetaldehyde as a product
  3. Produces acetate (acetic acid) as a product
  4. Is an isomerase
  5. Usually contain a different number of polypeptide chain's (subunits)
26. The Induced Fit Theory was an improvement over the Lock and Key Theory because the Induced Fit Theory
  1. Explained that conformational changes occurred as the reaction proceeded
  2. Recognized that the enzymes were flexible
  3. Explained how the topology of the active site was complementary to both the substrates and products
  4. Explained how charge distribution of the active site was complementary to the both the substrates and products
  5. All of the above are true
27. Allopurinol will inhibit all of the following conversions EXCEPT
  1. Guanine to urate
  2. GMP to urate
  3. Cytosine to urate
  4. Hypoxanthine to urate
  5. AMP to urate
28. Which of the following statements about the normal metabolism of alcohol by the enzyme Alcohol Dehydrogenase is NOT true
  1. Uses NAD+ as a substrate
  2. Produces NADH as a product
  3. Produces H+ as a product
  4. Is an oxidoreductase
  5. Uses acetaldehyde as a substrate
29. The reaction,
Fatty acid + CoA + ATP = Fatty acylCoA + AMP +PPi
is an example of
  1. Transferase
  2. Hydrolase
  3. Lyase
  4. Isomerase
  5. Ligase

Answers:

1. Answer: A. Chapter 8, Objective 1: Define catalytic power. Back to question 1.
2. Answer: E. Chapter 8, Objective 2: What is meant by substrate specificity of an enzyme? Back to question 2.
3. Answer: C. Chapter 8, Objective 3: What is the active site? Back to question 3.
4. Answer: D. Chapter 8, Objective 4: Explain the Induced Fit Theory Model for Substrate Binding. What was the major shortcoming of the Lock-and-Key Model for Substrate Binding? Back to question 4.
5. Answer: B. Chapter 8, Objective 5: Explain catalytic power in terms of the transition state and activation energy. Back to question 5.
6. Answer: A. Chapter 8, Objective 6: Be able to define the following terms: cofactor, coenzyme, and prosthetic group Back to question 6.
7. Answer: C. Chapter 8, Objective 7: What does an activation-transfer coenzyme do? Back to question 7.
8. Answer: E. Chapter 8, Objective 8: With respect to thiamine pyrophosphate, what vitamin is it synthesized from? What group on substrate (pyruvate or a-ketoglutarate for example) is always attacked by this coenzyme? Which bond is broken? Back to question 8.
9. Answer: C. Chapter 8, Objective 9: With respect to Coenzyme A, what vitamin is it synthesized from? What is its functional group on the coenzyme and what kind of bond does it form with the activated group? What types of groups are activated? Back to question 9.
10. Answer: B. Chapter 8, Objective 10: Concerning biotin, what kind of enzyme uses this coenzyme and what do they do? What is the vitamin? Is biotin a prosthetic group? Back to question 10.
11. Answer: B. Chapter 8, Objective 11: Concerning the cofactor pyridoxal phosphate, what type of group does it usually react with? What vitamins is it synthesized from (see your lecture notes or use the textbook index)? Back to question 11.
12. Answer: E. Chapter 8, Objective 12: Concerning NAD+, what vitamin is it synthesized from? When lactate dehydrogenase or alcohol dehydrogenase oxidize their substrates, what is transferred to NAD+? Besides pyruvate and acetaldehyde, what is the other reaction product? What is the function of the ADP portion of NAD+?

Back to question 12.
13. Answer: E. Chapter 8, Objective 13: Be able to draw a probable plot of activity versus pH for an enzyme that functions at pH=7.0. Back to question 13.
14. Answer: B. Chapter 8, Objective 14: Be able to draw a probable plot of activity versus temperature for a human enzyme. Back to question 14.
15. Answer: D. Chapter 8, Objective 15: What is the normal function of acetylcholinesterase? Explain how diisopropylphosphofluoridate causes the symptoms associated with it. Is this an irreversible inhibitor? Why? Back to question 15.
16. Answer: E. Chapter 8, Objective 16: How does aspirin inhibit prostaglandin endoperoxide synthase? Back to question 16.
17. Answer: C. Chapter 8, Objective 17: Concerning penicillin, why does it bind so readily to the active site of the enzyme? Is penicillin an irreversible inhibitor? Is penicillin a suicide inhibitor? Why? Back to question 17.
18. Answer: A. Chapter 8, Objective 18: What is the normal function of xanthine oxidase. Explain why allopurinol is used to treat gout. Is allopurinol an irreversible inhibitor? Is allopurinol a suicide inhibitor? Why? Back to question 18.
19. Answer: D. Chapter 8, Objective 10:What is the normal function of xanthine oxidase. Explain why allopurinol is used to treat gout. Is allopurinol an irreversible inhibitor? Is allopurinol a suicide inhibitor? Why? Back to question 19.
20. Answer: D. Chapter 8, Objectives 19: In general terms, why are heavy metals toxic? Back to question 20.
21. Answer: D. Chapter 8, Objectives 20: Be able to name the 6 major classes of enzymes. Given one of the following reactions, be able to match it with one of the 6 major classes of enzyme reactions catalyzed: alcohol dehydrogenase, glucokinase, chymotrypsin, aldolases, triosephosphate isomerase, and pyruvate carboxylase. Back to question 21.
22. Answer: C. Chapter 8, Objective 21: What is the difference between a synthase and a synthetase? Back to question 22.
23. Answer: E. Chapter 8, Objective 22: Concerning Dennis "the menace" Veere, Explain how Malathion causes the symptoms associated with it. Is the inhibition irreversible? Why? Is this an example of a suicide inhibitor? Why? Back to question 23.
24. Answer: C. Chapter 8, Objective 23: Concerning Lotta Topaigne, Explain why allopurinol is used to treat gout. What is the normal reaction inhibited by this drug? Is allopurinol an irreversible inhibitor? Is allopurinol a suicide inhibitor? Why? Back to question 24.
25. Answer: B. Chapter 8, Objective 24: Concerning Al Martini, be able to write the equation for the first step in alcohol metabolism in humans. What vitamin is the coenzyme of this reaction synthesized from? What is the common vitamin deficiency seen in alcoholics? Why does it occur? Back to question 25.
26. Answer: E. Chapter 8, Objective 4: Explain the Induced Fit Theory Model for Substrate Binding. What was the major shortcoming of the Lock-and-Key Model for Substrate Binding? Back to question 26.
27. Answer: C. Chapter 8, Objective 23: Concerning Lotta Topaigne, Explain why allopurinol is used to treat gout. What is the normal reaction inhibited by this drug? Is allopurinol an irreversible inhibitor? Is allopurinol a suicide inhibitor? Why? Back to question 27.
28. Answer: E. Chapter 8, Objective 20: Be able to name the 6 major classes of enzymes. Given one of the following reactions, be able to match it with one of the 6 major classes of enzyme reactions catalyzed: alcohol dehydrogenase, glucokinase, chymotrypsin, aldolases, triosephosphate isomerase, and pyruvate carboxylase. Back to question 28.
29. Answer: E. Chapter 8, Objective 20: Be able to name the 6 major classes of enzymes. Given one of the following reactions, be able to match it with one of the 6 major classes of enzyme reactions catalyzed: alcohol dehydrogenase, glucokinase, chymotrypsin, aldolases, triosephosphate isomerase, and pyruvate carboxylase. Back to question 29.