Questions:

1. For an enzyme that follows Michaelis-Menton kinetics, Km is equal to
  1. The [s] at one-half Vmax
  2. The vi at one-half Vmax
  3. The [s] at one-half vi
  4. The vi at one-tenth Vmax
  5. Two times the Vmax
2. Glucokinase and hexokinase are two enzymes that have the same substrates and products.  A plot of v versus [s] for glucokinase yields an S-shaped curve for glucokinase and a rectangular hyperbola for hexokinase.
  1. They are both Michaelis-Menten enzymes
  2. Only glucokinase is a Michaelis-Menten enzyme
  3. They both have the same Km
  4. They both have the same Vmax
  5. They are isozymes
3. Some patients with maturity onset diabetes of the young (MODY) have a a mutation in their pancreatic glucokinase.  This enzyme prevents enough insulin release because
  1. The S0.5 is too high so glucose is metabolized too fast
  2. The S0.5 is too low so glucose is metabolized too slow
  3. The S0.5 is too high so glucose is metabolized too slow
  4. The S0.5 is too low so glucose is metabolized too fast
  5. The S0.5 is too low so the Vmax is too high
4. When an enzyme that follows Michaelis-Menten kinetics is treated with a competitive inhibitor 
  1. The Km increases and the Vmax increases
  2. The Km stays the same and the Vmax increases
  3. The Km increases and the Vmax stays the same
  4. The Km decreases and the Vmax increases
  5. The Km decreases and the Vmax stays the same
5. When an enzyme that follows Michaelis-Menten kinetics is treated with a noncompetitive inhibitor 
  1. The Km increases and the Vmax increases
  2. The Km stays the same and the Vmax decreases
  3. The Km increases and the Vmax stays the same
  4. The Km decreases and the Vmax increases
  5. The Km decreases and the Vmax stays the same
6. If muscle cells in the fasting state have all the glucose-6-phosphate they need then hexokinase will be inhibited and all of the following will be true EXCEPT
  1. Glucose will leave the muscle cell as fast as it enters
  2. Conserved glucose can be used by tissues that need it
  3. Conserved glucose can be used by the brain
  4. Conserved glucose can be used by Red Blood Cells
  5. The liver will release glucose faster
7. Phosphofructokinase-1 is an enzyme in glycolysis that converts fructose-6-phosphate to fructose-1,6-bisphosphate.  AMP binds to this enzyme at sites other than the active sites and causes the reaction velocity to increase.  All of the following would be true of AMP EXCEPT
  1. AMP changes the conformation of the active sites when it binds the enzyme
  2. AMP changes the conformation of all the active sites on the enzyme
  3. AMP is a competitive inhibitor
  4. AMP is a positive allosteric effector
  5. AMP is an allosteric activator
8. When a substrate binds to an active site of an allosteric enzyme, all of the following happen EXCEPT
  1. The other active sites bind more substrate
  2. The conformation of the polypeptide forming the active site changes
  3. The conformation of all the active sites change
  4. The binding of a negative allosteric effector becomes more likely
  5. The binding of an allosteric activator becomes more likely
9. The T-conformation usually binds
  1. Substrate better than the R-conformation
  2. The positive allosteric effector better than the R-conformation
  3. Both substrate and allosteric activators better than the R-state
  4. Both substrate and allosteric inhibitors better than the R-state
  5. Allosteric inhibitors better than the R-conformation
10. The enzyme phosphofructokinase-1 is an allosteric enzyme and demonstrates a sigmoidal curve when vi is plotted against [S].  If a positive allosteric effector like AMP is added, then usually
  1. The concentration of substrate necessary to reach half maximal velocity will increase
  2. The conformation of the enzyme will not change
  3. The sigmoidal curve will become less sigmoidal and more like a rectangular hyperbola
  4. The sigmoidal curve will move to the right
  5. The S0.5 will become grater
11. A protein kinase might do all of the following EXCEPT
  1. Phosphorylate a seryl R-group
  2. Use ATP as a substrate
  3. Form a phosphoester bond with an alcohol group
  4. Phosphorylate a tyrosyl residue
  5. Run the same reaction as a protein phosphatase
12. Protein phosphatases are enzymes that do all of the following EXCEPT
  1. Hydrolyze phosphotyrosyl groups
  2. Hydrolyze glucosidic bonds
  3. Hydrolyze phosphoester bonds
  4. Make some enzymes more active
  5. Make some enzymes less active
13. Muscle glycogen phosphorylase can be activated by all of the following except
  1. The binding of AMP to allosteric sites
  2. The addition of phosphate to seryl residues
  3. The hydrolysis of phosphoester groups by protein phosphatase
  4. The addition of phosphate by glycogen phosphorylase kinase
  5. Both AMP and phosphorylation
14. Glycogen phosphorylase kinase is activated by all of the following except
  1. The increase in AMP from muscle contraction
  2. The increase in Ca++ during muscle contraction
  3. The increase in Ca++ binding to calmodulin
  4. The increase in protein kinase A activity
  5. The increase in phosphorylation by protein kinase A
15. When increased adrenalin binds to its receptor on muscle cells, there is an increase in glycogen breakdown.  All of the following are part of the process EXCEPT
  1. cAMP binds to the catalytic subunits of protein kinase A
  2. cAMP binds to regulatory units of protein kinase A
  3. The regulatory subunits of protein kinase A dissociate from the catalytic subunits
  4. Glycogen phosphorylase kinase is phosphorylated by protein kinase A
  5. Glycogen phosphorylase is phosphorylated by glycogen phosphorylase kinase
16. When an action potential travels across the membrane of a muscle cell, it causes a release of large amounts of calcium from the sarcoplasmic reticulum.  This in turn causes all of the following EXCEPT 
  1. An increase in Ca++-troponin C
  2. An increase in Ca++-calmodulin
  3. An increase in ADP and AMP production by contracting muscle
  4. An increase activation of glycogen phosphorylase by binding to AMP
  5. An increase activation of glycogen phosphorylase by binding to Ca++-calmodulin
17. All of the following are true of G-proteins EXCEPT
  1. G proteins all stay active for the same amount of time
  2. G proteins bind to and change the conformation of target proteins
  3. G proteins change their own conformation when they bind GTP
  4. G proteins change their own conformation when they hydrolyze GTP
  5. G proteins are GTPases (hydrolyze GTP)
18. Concerning Chymotrypsinogen, all the following are true except
  1. It is activated by proteolytic cleavage
  2. It is activated by hydrolysis of one or more peptide bonds
  3. It is an active enzyme
  4. It is a proenzyme
  5. It is a zymogen
19. One can measure the beginning of induction in bacteria in as soon as six minutes.  However, in humans, the induction times for the enzymes of pathways like gluconeogenesis and glycolysis take longer.  In humans, induction is usually noticeable in
  1. 10 to 20 minutes
  2. hours
  3. weeks
  4. months
  5. years
20. During fasting or infective stress, all of the following occur EXCEPT
  1. The concentration of cortisol in the blood and tissues rises
  2. Cortisol causes induction of mRNA and an increase in ubiquitin synthesis
  3. Ubiquitin is covalently attached to proteins destined to be catabolized into amino acids
  4. Cortisol represses mRNA nescessary for antibody synthesis
  5. More amino acids are made available for gluconeogenesis
21. All of the following are true for metabolic pathways EXCEPT.  The control enzyme
  1. Usually catalyses the fastest step
  2. Usually catalyses the committed step
  3. Is usually an allosteric enzyme
  4. Often undergoes feedback inhibition by the endproduct
  5. For an energy producing pathway is often inhibited by ATP or activated by AMP or ADP
22. All of the following are true EXCEPT.  The major enzyme reaction for metabolizing alcohol in most humans requires the
  1. Enzyme alcohol dehydrogenase
  2. Substrate NAD+
  3. Substrate acetate
  4. Production of acetaldehyde
  5. Production of NADH
23. Your patient is an alcoholic with a blood alcohol concentration of 1 mM.  Assume that the Vmax of cytosolic alcohol dehydrogenase enzyme and the MEOS system are equal and that the KM's are 0.04 mM and 11 mM, respectively.  The velocity of the
  1. Alcohol dehydrogenase system will be at one-half Vmax
  2. Alcohol dehydrogenase system will be at Vmax
  3. Alcohol dehydrogenase system will be at two times Vmax
  4. MEOS system will be at one-half Vmax
  5. MEOS system will be at Vmax
24. Your patient is an alcoholic that is drinking heavily for several days.  You would expect that
  1. Alcohol dehydrogenase is inhibited by high concentrations of NAD+
  2. Alcohol dehydrogenase is inhibited by a high ratio of NAD+ / NADH
  3. Product inhibition is not a factor
  4. The high NADH/NAD+ would inhibit the beta-oxidation of fatty acids
  5. The MEOS system would not yet be induced
25. Concerning Ann O’Rexia, in _______she can convert glucose to ______ using the enzyme _______________. 
  1. Liver :             glucose-6-phosphate:              hexokinase
  2. Muscle :          glucose-6-phosphate:              glucokinase
  3. Liver :             glucose-6-phosphate:              glucokinase
  4. Muscle :          fructose-6-phosphate:              glucokinase
  5. Liver :             fructose-6-phosphate:              hexokinase
26. All of the following are true about glycolysis in muscle EXCEPT
  1. Glycolysis can be feedback inhibited
  2. The glycolytic pathway can be used to extract energy from glucose
  3. ATP can act as a feedback inhibitor of the pathway
  4. AMP can act as an activator of the pathway
  5. AMP is a negative allosteric effector of the pathway
27. Concerning Ann O'Rexia, when she stores blood glucose as glycogen in the liver, the process is
  1. Not dependent on the use glucokinase
  2. Called glycogenolysis
  3. Called glycogen catabolism
  4. Not dependent upon the concentration of glucose
  5. Enhanced by the presence of insulin
28. Ann O'Rexia suffers from anorexia and eats nothing before jogging in the morning.  She complains that she feels tired.  One of the reasons she feels tired is that her
  1. Pathway for glycogenolysis is inhibited
  2. Pathway for the catabolism of glycogen is inhibited
  3. Pathway for glycolysis is inhibited
  4. Glycogen stores are low
  5. Insulin stores are low
29. When Ann O’Rexia begins to jog, all of the following occur EXCEPT
  1. Muscle glycogen phosphorylase combines with AMP and becomes active
  2. Glucagon inhibits the cAMP cascade in liver
  3. Epinephrine increases in the blood and stimulates the cAMP cascade
  4. Liver glycogen phosphorylase kinase is activated by protein kinase A
  5. Glycogen phosphorylase kinase phosphorylates glycogen phosphorylase
30. When Ann O'Rexia begins to jog, an enzyme in muscle glycolysis is activated by the following mechanism
  1. Increased ATP allosterically activates phosphofructokinase-1
  2. Increased AMP allosterically activates phosphofructokinase-1
  3. Increased AMP allosterically activates glucokinase
  4. Ca++ allosterically activates glucokinase
  5. Ca++ allosterically activates hexokinase
31. Isoenzymes (isozymes)
  1. Produce different products
  2. Use different substrates
  3. Have the same electrophoretic mobilities
  4. Have different amino acid sequences
  5. Removes alcohol from the system by reducing it
32. The enzyme phosphofructokinase-1 is an allosteric enzyme and demonstrates a sigmoidal curve when vi is plotted against [S].  If a positive allosteric effector like AMP is added, then usually
  1. The concentration of substrate necessary to reach half maximal velocity will increase
  2. The conformation of the enzyme will not change
  3. The sigmoidal curve will become a straight line
  4. The sigmoidal curve will move to the right
  5. The S0.5 will become smaller
33. When looking at a graph of vi versus [S] for a Machaelis-Menten enzyme, Vmax is found
  1. At the Km
  2. At a Vi equal to the Km
  3. When the substrate concentration is higher than the Km
  4. When the substrate level is below the Km
  5. When the curve is S-shaped
34. Fructose-1,6-bisphosphatase is an enzyme in gluconeogenesis that converts fructose-1,6-bisphosphate to fructose-6-phosphate. The metabolite (organic molecule) Fructose-2,6-bisphosphate binds to this enzyme at sites other than the active sites and causes the reaction velocity to decrease. All of the following would be true of Fructose-2,6-bisphosphate EXCEPT
  1. Fructose-2,6-bisphosphate changes the conformation of the active sites when it binds the enzyme
  2. Fructose-2,6-bisphosphate changes the conformation of all the active sites on the enzyme
  3. Fructose-2,6-bisphosphate is a competitive inhibitor
  4. Fructose-2,6-bisphosphate is a negative allosteric effector
  5. Fructose-2,6-bisphosphate is an allosteric inhibitor

Answers:

1. Answer: A. Chapter 9, Objective 1: What are the terms found in the Machaelis-Menten equation and what do they mean? Draw a graph of vi versus [S] for a hypothetical Machaelis-Menten enzyme. What kind of curve is derived? Where are Vmax and KM on this curve? Back to question 1.
2. Answer: E. Chapter 9, Objective 2: Are glucokinase and hexokinase isozymes? Is hexokinase a Machaelis-Menten enzyme? Is glucokinase of liver or pancreas a Machaelis-Menten enzyme? Back to question 2.
3. Answer: C. Chapter 9, Objective 3: How does the S0.5 for pancreatic glucokinase in some patients with MODY compare with normal patients? What effect does this have on insulin production and blood glucose levels? Back to question 3.
4. Answer: C. Chapter 9, Objective 4: What is the effect of a competitive inhibitor on the KM and Vmax? Back to question 4.
5. Answer: B. Chapter 9, Objective 5: What is the effect of a noncompetitive inhibitor on the KM and Vmax? Back to question 5.
6. Answer: E. Chapter 9, Objective 6: How does product inhibition of hexokinase in one cell benefit all the other cells of the body? Back to question 6.
7. Answer: C. Chapter 9, Objective 7: What are the various names for the compounds that bind to an allosteric site? What affect do they have on the enzyme? Back to question 7.
8. Answer: D. Chapter 9, Objective 8: The substrates of allosteric enzymes exhibit positive cooperativity. Explain positive cooperativity in terms of subunits, conformation, and activity of the active site. Back to question 8.
9. Answer: E. Chapter 9, Objective 9: What is the difference between the T-conformation (state) and the R-conformation of an allosteric enzyme? Back to question 9.
10. Answer: C. Chapter 9, Objective 10: Objective 10: Understand the effect that allosteric activators and inhibitors have on the conformation of an allosteric enzyme and on the plot of velocity versus substrate concentration. What about the S0.5? Back to question 10.
11. Answer: E. Chapter 9, Objective 11: What is the general name for the enzyme that places phosphate groups onto an.enzymes? What groups on the enzymes are typically phosphorylated? What are the effects of phosphorylation? Back to question 11.
12. Answer: B. Chapter 9, Objective 12: What is the general name for the enzymes that hydrolyze and thus remove phosphate groups from proteins? What bond is usually broken? What are the effects of dephosphorylation? Back to question 12.
13. Answer: C. Chapter 9, Objective 13: Using the terms seryl residue, phosphorylation, positive allosteric effector allosteric site, phosphorylase b, phosphorylase a, conformation, and enzyme activity, explain how either AMP or phosphorylase kinase activates muscle glycogen phosphorylase. What is the effect of protein phosphatase upon phosphorylase a? Back to question 13.
14. Answer: A. Chapter 9, Objective 14: What are the activators of phosphorylase kinase in a muscle cell? Back to question 14.
15. Answer: A. Chapter 9, Objective 15: Starting with an increase in the concentration of cAMP that resulted from adrenalin binding to a receptor in the cell membrane, explain how phosphorylase is activated. How does the cascade result in the amplification of the original signal? Back to question 15.
16. Answer: E. Chapter 9, Objective 16: Explain how an increase in calcium in muscle cells simultaneously activates muscle contraction and glycogenolysis. Which system uses ATP and which helps to produce ATP? Back to question 16.
17. Answer: A. Chapter 9, Objective 17: How do G-proteins function? No need to mention GAPs, GEFs, GDIs, or the Ras family at this time. Back to question 17.
18. Answer: C. Chapter 9, Objective 18: Are chymotrypsinogen and prothrombin zymogens? How are these enzymes activated? Back to question 18.
19. Answer: B. Chapter 9, Objective 19: What is the time frame of induction or repression? Back to question 19.
20. Answer: D. Chapter 9, Objectives 20: Name one hormone that induces ubiquitin in muscle tissue. What is the function of this process, i.e., what is the result of ubiquitin induction? Back to question 20.
21. Answer: A. Chapter 9, Objectives 21: Why is it important that the regulatory (control) enzyme for a pathway, catalyze the rate limiting step in a pathway? How is the rate of this step (enzyme) controlled? What does the term committed step mean? Back to question 21.
22. Answer: C. Chapter 9, Objective 22: Concerning Al Martini, what are the two principal mechanisms for catabolizing ethanol in humans? Be able to write the reaction for the most common mechanism that uses NAD+ as a cofactor. Back to question 22.
23. Answer: B. Chapter 9, Objective 23: Concerning Al Martini, assume that the Vmax of cytosolic alcohol dehydrogenase enzyme and the MEOS system are equal in Al's liver and that the KM's are 0.04 mM and 11 mM, respectively. Which will oxidize most of the alcohol consumed when the blood alcohol content is low. For example, after consuming 1 oz of alcohol and a blood alcohol of 6.4 mM. Why? Back to question 23.
24. Answer: D. Chapter 9, Objective 24: Concerning Al Martini, explain how increasing the amount of alcohol oxidized by alcohol dehydrogenase will affect the rate at which alcohol is oxidized. How does this affect fatty acid oxidation? Back to question 24.
25. Answer: C. Chapter 9, Objective 25: Concerning Ann O'Rexia, in which of her tissues do you find hexokinase and glucokinase and what is the reaction these enzymes catalyze? When glucose-6-phosphate inhibits hexokinase, is this product inhibition? Back to question 25.
26. Answer: E. Chapter 9, Objective 26: Concerning Ann O'Rexia, what pathway is used when her cells wants to make energy from glucose-6-phosphate and how does the concentration of ATP in the cell affect the rate of this reaction? Is this feedback regulation? How does the concentration of AMP affect the rate of this reaction? Would you call this feedback or feed forward regulation? Is this positive allosteric regulation? Back to question 26.
27. Answer: E. Chapter 9, Objective 27: Concerning Ann O'Rexia, what pathway does she use for the storage of glucose as glycogen? How does glucose concentration and insulin affect this pathway? Is this feed forward regulation? Back to question 27.
28. Answer: D. Chapter 9, Objective 28: Concerning Ann O'Rexia who suffers from anorexia, if joging activates both glycogenolysis and glycolysis, why does Ann tire easily? Back to question 28.
29. Answer: B Chapter 9, Objective 29:Concerning Ann O'Rexia, when she begins to jog, what muscle enzyme in glycogenolysis is activated by AMP? What type of activation is this? How does epinephrine activate this same enzyme? What role does cAMP and protein kinase A play in this cascade? Back to question 29.
30. Answer: B Chapter 9, Objective 30: Concerning Ann O'Rexia, when she begins to jog, what enzyme in glycolysis is activated? What type of activation is this? Back to question 30.
31. Answer: D. Chapter 9, Objective 2: Are glucokinase and hexokinase isozymes? Is hexokinase a Machaelis-Menten enzyme? Is glucokinase of liver or pancreas a Machaelis-Menten enzyme? Back to question 31.
32. Answer: E. Chapter 9, Objective 10: Objective 10: Understand the effect that allosteric activators and inhibitors have on the conformation of an allosteric enzyme and on the plot of velocity versus substrate concentration. What about the S0.5? Back to question 32.
33. Answer: C. Chapter 9, Objective 1: What are the terms found in the Michaelis-Menten equation and what do they mean? Draw a graph of vi versus [S] for a hypothetical Machaelis-Menten enzyme. What kind of curve is derived? Where are Vmax and Km on this curve? Back to question 33.
34. Answer: C. Chapter 9, Objective 7: What are the various names for the compounds that bind to an allosteric site? What affect do they have on the enzyme? Back to question 34.