Examination 3: Chapters 19 through 21

This exam combines questions from exams given during past years. Remember that the final exam will also include questions from the board review book. 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. Which of the following terms are used to describe a reaction when the substrates and products of the reaction are at any concentration?
  1. Delta G
  2. Delta Go
  3. Delta Go'
  4. -T delta S
  5. Delta H
2. For the enzyme reaction A+ B = C + D, Delta Go' = + 1 kcal/mol. This reaction will proceed spontaneously in a forward direction if:
  1. The concentration of D is increased one-hundred fold
  2. The concentration of C is increased one-hundred fold
  3. The concentration of A is increased one-hundred fold
  4. The concentration of B is lowered one-hundred fold
  5. The concentration of both A and D are increased one-hundred fold
3. During muscle contraction:
  1. ATP binds to the actin-ATPase
  2. Low calcium concentration allows interaction of myosin and actin
  3. ATP hydrolysis causes necessary changes in conformation
  4. Binding of ATP to actin allows association of actin and myosin
  5. AMP is the product of ATP hydrolysis
4. Oxidative phosphorylation:
  1. Is anaerobic
  2. Requires AMP
  3. Requires the electron transport system
  4. Is not dependent upon development of a proton gradient
  5. Is independent of mitochondria
5. Patients with hyperthyroidism complain constantly of feeling hot and sweaty. All of the following are reasons EXCEPT:
  1. Thyroid hormone induces many proteins that catalyze the oxidation of fats, carbohydrates, and proteins
  2. Thyroid hormone stimulates the Na+,K+-ATPase
  3. Thyroid hormone increases the flux through most anabolic pathways
  4. All spontaneous reactions convert some free energy to heat
  5. Thyroid hormone causes the non-enzymatic hydrolysis of ATP
6. Which of the following is not a function of the citric acid cycle?
  1. Catabolism of carbon structures of some amino acids
  2. Catabolism of acetate groups from acetyl CoA
  3. The production of GTP
  4. The production of NADPH
  5. The production of carbon structures for the synthesis of some amino acids
7. In the citric acid cycle, a substrate level phosphorylation is catalyzed by:
  1. Citrate synthase
  2. Succinyl CoA synthetase
  3. Fumarase
  4. Isocitrate dehydrogenase
  5. Citrate lyase
8. In contrast to NADH, FADH:
  1. Can donate electrons, but only two at a time, in a chemical reaction
  2. Has a low affinity for its apoenzyme
  3. Is very reactive in solution
  4. Is an excellent feedback inhibitor
  5. Is derived from a vitamin
9. The anaplerotic reaction that links glycolysis to the TCA cycle:
  1. Uses thiamin as a cofactor
  2. Is called phosphoenolpyruvate carboxykinase
  3. Produces oxaloacetate
  4. Is activated by malonyl CoA
  5. Is dependent upon vitamin B12
10. Which of the following two enzymes are thought to be the major control enzymes of the TCA cycle?
  1. Malate dehydrogenase and fumarase
  2. Succinate dehydrogenase and fumarase
  3. Succinyl CoA synthetase and succinate dehydrogenase
  4. Succinyl CoA synthetase and alpha-ketoglutarate dehydrogenase
  5. Alpha-ketoglutarate dehydrogenase and isocitrate dehydrogenase
11. Wet beriberi results in low peripheral resistance and cardiomyopathy. Both of these symptoms are explained as follows:
  1. Thiamin pyrophosphate is a cofactor for pyruvate carboxylase
  2. Without thiamin, the TCA cycle produces too much ATP
  3. Thiamin is an important intermediate in the electron transport chain
  4. Without thiamin, energy cannot be produced by muscle cells
  5. Thiamin permeabilizes membranes so no proton gradient can be established
12. The ATP synthase responsible for most of the ATP synthesis in the body is located:
  1. On the outer side of the outer mitochondria membrane
  2. On the inner side of the outer mitochondria membrane
  3. On the outer side of the inner mitochondria membrane
  4. On the inner side of the inner mitochondria membrane
  5. Free in the matrix of the mitochondria
13. If an electron were removed from alpha-ketoglutarate and you could watch it move down the electron transport system, the order of movement would be as follows:
  1. NADH, Complex I, CoQ, Complex III, Cytochrome C, Complex IV, H2O
  2. NADH, Complex I, Complex II, CoQ, Cytochrome C, Complex IV, H2O
  3. NADH, Complex II, CoQ, Cytochrome C, Complex III, Complex IV, H2O
  4. NADH, Complex I, CoQ, Complex II, Cytochrome C, Complex III, H2O
  5. NADH, Complex I, Complex II, Cytochrome C, Complex III, CoQ, Complex IV, H2O
14. Which of the following statements does NOT help explain the chemiosmotic theory?
  1. Protons move down a concentration gradient with negative free energy change
  2. ADP and Pi combine to form ATP, this reaction has a positive change in free energy
  3. The inner mitochondria membrane is impermeable to protons
  4. The only way protons can enter the mitochondria is through the ATP synthase with the concomitant synthesis of ATP
  5. The outside of the mitochondria is negative with respect to the matrix
15. A mitochondrion is producing ATP at a constant rate and, then, a chemical uncoupler is added. Compared to before the uncoupler was added:
  1. Less heat would be produced
  2. Less water would be produced
  3. More NADH would be oxidized
  4. More ATP would be produced
  5. The proton gradient across the membrane would be increased
16 Regarding Cora Nari, which of the following statements about her heart attack and subsequent treatment and effects are FALSE?
  1. Tissue plasminogen activator causes an increased production of plasmin
  2. Tissue plasminogen activator can be given following a heart attack to dissolve blood clots
  3. Because of its high energy demands, the normal heart relies on anaerobic respiration to meet its needs
  4. Nitroprusside can be given following a heart attack to dilate blood vessels
  5. Cardiac muscle cells, sperm cells, and other active cells have a relatively high number of mitochondria
17. The cleavage of the high-energy bond of ATP into ADP and Pi is an example of what type of reaction?
  1. Oxidation-reduction
  2. Phosphorylation
  3. Acetylation
  4. Hydrolysis
  5. Amination
18. Delta-G is negative, Delta-Go' is positive. Will the reaction occur spontaneously?
  1. Yes
  2. No
  3. Not enough information to determine the answer
19. Which of the following is NOT an example in which ATP is utilized in the body for work?

  1. Contraction of muscle
  2. Entry of water into cells through specific pores
  3. Phosphorylation of glucose by hexokinase
  4. Maintenance of the Na+ and K+ concentration gradients
  5. Formation of glycosidic bonds to make glycogen
20. Which of the following is NOT a step during muscle contraction?
  1. The terminal end of a myosin filament binds ATP
  2. Cleavage of ADP into AMP and Pi provides energy for mechanical work
  3. Thick myosin filaments bind thin actin filaments
  4. Presence of calcium enables myosin to bind actin
  5. ATP is cleaved by an ATPase located on the myosin filament

21. The phosphorylation of glucose to glucose-6-phosphate has a Delta Go'of +3.3 kcal/mol. So why does the reaction occur in almost every cell of our body?
  1. Glucose becomes unstable intracellularly
  2. Hexokinase is present
  3. ATP hydrolysis
  4. High concentration of glucose in the blood compared to cell
  5. This reaction is coupled to another that has a much higher positive Delta Go
22.

Which of the following statements regarding electron-accepting coenzymes is INCORRECT?

  1. FAD accepts electrons as the hydrogen atom
  2. NADH is the reduced form of the coenzyme
  3. FAD(H2) is synthesized from the vitamin riboflavin
  4. The Delta Go' for the oxidation of NADH by the electron transport chain is negative
  5. The electrons donated to these coenzymes are subsequently removed by the enzymes of the TCA cycle
23. Which of the following statements regarding the TCA cycle is CORRECT?
  1. The rate-limiting step involves the enzyme malate dehydrogenase
  2. For each acetyl CoA entering the cycle, two molecules of CO2 are produced
  3. For each acetyl CoA entering the cycle, 24 high-energy phosphate bonds are produced
  4. The cycle will not function unless glutamate is present
  5. The TCA cycle occurs in the rough endoplasmic reticulum of virtually every cell in the body
24. Which of the following statements regarding the alpha-ketoglutarate dehydrogenase complex is INCORRECT?
  1. One of its coenzymes - lipoic acid - comes from the vitamin B-carotene
  2. It requires FAD as a coenzyme
  3. Carbon dioxide is produced by this complex
  4. One of its coenzymes - CoASH - comes from the vitamin pantothenate
  5. It catalyzes the reaction converting a-ketoglutarate into succinyl CoA
25. Which enzyme complex in the TCA cycle requires the cofactors thiamine pyrophosphate, lipoic acid, CoA, FAD and NAD+?
  1. Citrate synthase
  2. a-ketoglutarate dehydrogenase
  3. Succiny-CoA synthetase (succinate thiokinase)
  4. Malate dehydrogenase
  5. Fumarase
26. Which of the following statements about the coenzyme FAD is INCORRECT?
  1. It accepts single electrons
  2. The TCA cycle enzyme that transfers electrons to FAD is found in the inner mitochondrial membrane
  3. It is very reactive in solution
  4. It remains tightly bound to the holoenzyme
  5. FADH2 is an important allosteric inhibitor of the TCA cycle

27. Which of the following statements about the TCA cycle is CORRECT?
  1. Citrate is frequently used for gluconeogenesis in the liver
  2. The production of oxaloacetate by pyruvate carboxylase is one of several anaplerotic reactions for the TCA cycle
  3. Succinyl CoA is used to create a neurotransmitter in the brain
  4. Pyruvate dehydrogenase helps convert pyruvate into malate
  5. Pyruvate carboxylase is only found in RBCs

28. Which of the following statements regarding the pyruvate dehydrogenase complex is INCORRECT?
  1. When the complex is phosphorylated, it is inactive
  2. Binding of pyruvate to the enzyme complex decreases the activity of the kinase
  3. High [ADP] stimulates the conversion of pyruvate to acetyl CoA
  4. The phosphatase which activates the complex is itself inhibited by Ca2+
  5. The kinase associated with the pyruvate dehydrogenase complex is an enzyme that adds phosphate groups

29. Which of the following statements regarding Complex II is INCORRECT?
  1. This is one means by which the TCA cycle is linked to the electron-transport chain
  2. Succinate dehydrogenase is embedded in the inner mitochondrial membrane
  3. Neither the single- or 2-electron forms of FAD dissociate from the enzyme
  4. Complex II transfers its electrons directly to cytochrome c
  5. The transfer of electrons from FAD to the electron-transport chain results in the synthesis of approximately 2 ATPs

30. Which of the following are in the correct sequence?
  1. Cytochrome Q; NADH dehydrogenase; Cytochrome c; Cytochrome oxidase
  2. Complex I; Cytochrome c; Complex II; Cytochrome oxidase
  3. NADH dehydrogenase; Cytochrome b-c1; Cytochrome c; Cytochrome oxidase
  4. Succinate dehydrogenase; Coenzyme Q; Cytochrome oxidase; Cytochrome c
  5. Complex I; Complex II; Coenzyme Q; Cytochrome oxidase

31. All of the following can act as "uncouplers" EXCEPT:
  1. Brown adipose tissue
  2. Proton ionophores
  3. Thermogenin (in infants)
  4. Thyroid hormone
  5. Cyanide
32. A patient suffers a heart attack due to the blockage of an artery. The heart cells downstream from the blockage will receive less oxygen which will in turn cause
  1. [ATP] to increase
  2. [ADP] to decrease
  3. An increase in electron flow through the electron transport chain
  4. [NADH] to increase
  5. Anaerobic glycolysis to decrease
33.

A patient has hyperthyroidism. Compared to normal, you would expect that the electron transport chain would

  1. increase electron flow (flux) through the chain
  2. decrease the oxidation of NADH
  3. decrease the production of water
  4. decrease the pumping of protons across the membrane
  5. increase its efficiency in terms of ATP production per NADH oxidized
 
ANSWERS

Correct answers and percentage of the class answering correctly. As a reference point, previous classes scored a combined mean of 77% for questions 1 through 33.

1: A, 90%. Chapter 19, Objective 4: "Understand the difference between delta-G and delta-G0!."

2: C, 86%. Chapter 19, Objective 9: "Given the equation at the bottom of Table 19.2, be able to explain why Delta-G can be positive while Delta-Go! is negative and visa versa"

3: C, 82%. Chapter 19, Objective 5: "Be able to explain how the free energy of ATP can be used to contract a muscle"

4: C, 99%. Chapter 19, Objective 14: "What is oxidative phosphorylation?"

5: E, 59%. Chapter 21, Objective 22: " Concerning X.S.Teefore, Explain how the affect of excess thyroid hormone on oxidative phosphorylation could explain increased appetite and sweating?"

6: D, 82%. Chapter 20, Objective 1: "To understand or describe any pathway or cycle, start with the following paradigm for the TCA cycle: Names, Functions, Substrates, Product, Control Enzymes, Regulation, Compartment, Tissues of Interest:"

7: B, 90%. Chapter 20, Objective 4: "Name the enzyme of the TCA cycle that catalyzes a substrate level phosphorylation. What are the substrates and products of this reaction?"

8: C, 50%. Chapter 20, Objective 6: "Compare NADH and FADH with respect to: (1) Mechanism of accepting or donating electrons, (2)Affinity for the apoenzyme, (3) reactivity in solution, and (4) ability to act as a feedback inhibitor or activator."

9: C, 71%. Chapter 20, Objective 20: "Be able to fully describe the anaplerotic reaction that links glycolysis and the TCA cycle. Name the enzyme, substrate, product, biological compartment and tissues of interest. Name the regulatory factor (activator) and explain how the system regulates the production of the TCA cycle intermediate. What coenzyme is used in the reaction?"

10: E, 91%. Chapter 20, Objective 12: "Name two control enzymes of the TCA cycle."

11: D, 74%. Chapter 20, Objective 29: "Concerning Al Martini...Given that a-ketoacids build up in the heart in wet beriberi, develop a scenario that would explain why peripheral vessels dilate and cardiac muscles loose their contractility."

12: D, 82%. Chapter 21, Objective 1: " Be able to draw a cartoon demonstrating oxidative phosphorylation. Include NADH, complexes I, II, III and IV, CoQ, cytochrome c, and ATP synthase. Demonstrate the sites for the pumping of protons and the direction of movement. Indicate the excess protons on one side of the membrane. Draw equations showing the synthesis of H2O and ATP."

13: A, 93%. Chapter 21, Objective 1: "Be able to draw a cartoon demonstrating oxidative phosphorylation. Include NADH, complexes I, II, and III, CoQ, cytochrome C, and ATP synthase. Demonstrate the sites for the pumping of protons and the direction of movement. Indicate the excess protons on one side of the membrane. Draw equations showing the synthesis of H2O and ATP."

14: E, 82%. Chapter 21, Objective 8: "Be able to state the chemiosmotic theory."

15: C, 69%. Chapter 21, Objective 16: "Understand how a chemical uncoupler works. What happens to heat production, ATP synthesis, and NADH utilization following uncoupling?"

16: C, 93% Ch. 21, Objectives 19 and 20,"Concerning Cora Nari: She had a heart attack. Why was nasal oxygen administered? Why was her blood pressure lowered? What might have been the effect on ATP production if nitroprusside had been continued for several days?" "Concerning Cora Nari: What is TPA and how does it dissolve blood clots?"

17: D, 94% Ch. 19, Objective 1, "Summarize the ATP-ADP cycle including the types of fuels used and the work accomplished."

18: A, 48% Ch. 19, Objective 4: "Understand the difference between delta-G and delta-G0!."

19: B, 81% Ch.19, Objective 1, "Summarize the ATP-ADP cycle including the types of fuels used and the work accomplished."

20: B, 81% Ch. 19, Objective 5: "Be able to explain how the free energy of ATP can be used to contract a muscle"

21: C, 94% Ch. 19, Objective 7, "Be able to explain how the free energy in ATP can be used to synthesize glucose-6-phosphate from glucose and phosphate even though this reaction is endergonic."

22: E, 70% Ch. 19, Objective 16, "How do NAD, FAD, and FMN function?"

23: B, 88% Ch. 20, Objective 1, "To understand or describe any pathway or cycle, start with the following paradigm for the TCA cycle: Names, Functions, Substrates, Product, Control Enzyme, Regulation, Compartment, Tissues of interest"

24: A, 82% Ch. 20, Objective 8, " Name the five cofactors of the a-ketoglutarate dehydrogenase reaction. Name the vitamins from which four of them are derived! What is the advantage of a multienzyme complex?"

25: B, 82% Ch. 20, Objective 8, " Name the five cofactors of the a-ketoglutarate dehydrogenase reaction. Name the vitamins from which four of them are derived! What is the advantage of a multienzyme complex?"

26: E, 72% Ch.20, Objective 6, "Compare NADH and FADH with respect to 1)mechanism of accepting or donating electrons 2)affinity for the apoenzyme 3)reactivity in solution, and 4) ability to act as a feedback inhibitor or activator"

27: B, 87% Ch.20, Objectives 19 and 20, "If TCA cycle intermediates are constantly being removed for biosynthesis, why doesn't the cycle stop?" " Be able to fully describe the anaplerotic reaction that links glycolysis and the TCA cycle. Name the enzyme, substrate, product, biological compartment and tissues of interest. Name the regulatory factor (activator) and explain how the system regulates the production of the TCA cycle intermediate. What coenzyme is used in the reaction?"

28: D, 71% Ch.20, Objective 16, "Explain how the rate of the pyruvate dehydrogenase complex is related to the rate of utilization of ATP."

29: D, 69% Ch.21, Objective 3, "Where is complex II found? What reaction of the TCA cycle does it catalyze? How much ATP is produced by this reaction? Which complexes couple proton pumping and succinate oxidation?

30: C, 70%, Ch. 21, Objective 1, "Be able to draw a cartoon demonstrating oxidative phosphorylation. Include NADH, complexes I, II, III, and IV, CoQ, cytochrome c, and ATP synthase. Demonstrate the sites for the pumping of protons and the direction of movement. Indicate the excess protons on one side of the membrane. Draw equations showing the synthesis of H2O and ATP."

31: E, 40% Ch. 21, Objectives 16 and 17, "Understand how a chemical uncoupler works. What happens to heat production, proton pumping, ATP synthesis, and NADH utilization following uncoupling?" " What is the difference between an inhibitor of electron transport and an uncoupler of electron transport with respect to NADH utilization, proton pumping, and ATP synthase?"

32: D, 65%, Ch 21, Objectives 11 and 21, "What portion of the ETC is inhibited by CN-? What is the effect of cyanide inhibition upon proton pumping and ATP synthesis?" "Concerning Cora Nari: How did the change in the ratio of ATP to ADP and AMP affect anaerobic glycolysis? How did this affect the pH?"

33: A, 68%, Ch 21, Objective 22 "Concerning X.S.Teefore, Explain how the affect of excess thyroid hormone on oxidative phosphorylation could explain increased appetite and sweating?"

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