Life 9e



Test File

to accompany

Life: The Science of Biology, Ninth Edition

Sadava • Hillis • Heller • Berenbaum

Chapter 9: Pathways that Harvest Chemical Energy

TEST FILE QUESTIONS

(By Catherine Ueckert)

Multiple Choice

1. Metabolic syndrome is a disorder with several symptoms including obesity. An experimental drug, Aicar, may aid in treating this disorder. It works by

a. increasing the rate of glucose oxidation.

b. decreasing oxidative phosphorylation from ATP.

c. increasing the breakdown of fat to yield ATP.

d. stimulating production of fast-twitch muscle fibers.

e. converting slow-twitch muscle fibers into fast-twitch muscle fibers.

Answer: c

Textbook Reference: 9.0 Of mice and marathons

Page: 168–169

Bloom’s Category: 2. Understanding

2. Which of the following statements about metabolic pathways is false?

a. The product of one reaction becomes the reactant for the next reaction.

b. They are a series of enzyme-catalyzed reactions.

c. Almost all are anabolic.

d. They are similar in all organisms.

e. Many are compartmentalized in eukaryotes.

Answer: c

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 169

Bloom’s Category: 2. Understanding

3. Which of the following statements about metabolic pathways is true?

a. Complex chemical transformations in the cell occur in a single reaction.

b. Each reaction requires oxygen.

c. In eukaryotes, they occur in the cytoplasm.

d. They vary from organism to organism.

e. Each one is regulated by specific enzymes.

Answer: e

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 169

Bloom’s Category: 2. Understanding

4. When a molecule loses hydrogen atoms (as opposed to hydrogen ions), it becomes

a. reduced.

b. oxidized.

c. redoxed.

d. hydrogenated.

e. hydrolyzed.

Answer: b

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 169

Bloom’s Category: 1. Remembering

5. ATP is

a. a short-term energy-storage compound.

b. the cell’s principal compound for energy transfers.

c. synthesized within mitochondria.

d. the molecule all living cells rely on to do work.

e. All of the above

Answer: e

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 2. Understanding

6. In the conversion of succinate to fumarate, hydrogen atoms are transferred to FAD. The conversion of succinate and FAD to fumarate and FADH2 is an example of

a. hydrolysis.

b. an allosteric reaction.

c. a metabolic pathway.

d. an aerobic reaction.

e. a redox reaction.

Answer: e

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 3. Applying

7. The oxidation of malate to oxaloacetate is coupled to the reduction of NAD+ to NADH + H+. NAD+ is a(n)

a. reducing agent.

b. oxidizing agent.

c. vitamin.

d. phosphate ester.

e. phosphorylating agent.

Answer: b

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 2. Understanding

8. In all cells, glucose metabolism begins with

a. glycolysis.

b. fermentation.

c. pyruvate oxidation.

d. the citric acid cycle.

e. chemosmosis.

Answer: a

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 1. Remembering

9. When NADH donates two electrons to ubiquinone during respiration, ubiquinone is

a. reduced.

b. oxidized.

c. phosphorylated.

d. aerobic.

e. hydrolyzed.

Answer: a

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 3. Applying

10. Which of the following processes occurs when oxygen is unavailable?

a. Pyruvate oxidation

b. The citric acid cycle

c. Fermentation

d. An electron transport chain

e. All of the above

Answer: c

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 2. Understanding

11. Which of the following oxidizes other compounds by gaining free energy and hydrogen atoms and reduces other compounds by giving up free energy and hydrogen atoms?

a. Vitamins

b. Adenine

c. ATP

d. NAD

e. Riboflavin

Answer: d

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 2. Understanding

12. The function of NAD+ is to

a. cause the release of energy to adjacent cells when energy is needed in aerobic conditions.

b. hasten the release of energy when the cell has been deprived of oxygen.

c. carry hydrogen atoms and free energy from compounds being oxidized and to give hydrogen atoms and free energy to compounds being reduced.

d. block the release of energy to adjacent cells.

e. None of the above

Answer: c

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 2. Understanding

13. NAD

a. is a key electron carrier in redox reactions.

b. requires oxygen to function.

c. is found only in prokaryotes.

d. binds with an acetyl group to form acetyl CoA.

e. detoxifies hydrogen peroxide.

Answer: a

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 1. Remembering

14. In the cell, the site of oxygen utilization is the

a. nucleus.

b. chloroplast.

c. endoplasmic reticulum.

d. mitochondrion.

e. cytosol.

Answer: d

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171–172

Bloom’s Category: 1. Remembering

15. Glycolysis converts glucose into pyruvate, ATP, and NADH. The process requires

a. oxygen, ATP, and a series of reactions.

b. carbon dioxide, 5 enzyme-catalyzed reactions, and glucose to begin the series of reactions.

c. pyruvic acid, oxygen, and enzymes to oxidize glucose inside the mitochondria

d. the pyruvate dehydrogenase complex to catalyze the reactions.

e. 10 enzyme-catalyzed reactions, each reaction dependent on the products of the previous reaction to proceed.

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 172

Bloom’s Category: 2. Understanding

16. For glycolysis to continue, all cells require

a. a respiratory chain.

b. oxygen.

c. mitochondria.

d. chloroplasts.

e. NAD+.

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 172

Bloom’s Category: 2. Understanding

17. During the energy-priming portion of glycolysis, the phosphates from ATP molecules are

a. added to the first and sixth carbons.

b. added to the second and fourth carbons.

c. wasted, as an energy investment.

d. used to make pyruvate.

e. used to make lactate.

Answer: a

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

Bloom’s Category: 3. Applying

18. The oxidation of pyruvate to carbon dioxide is called

a. fermentation.

b. the citric acid cycle.

c. glycolysis.

d. oxidative phosphorylation.

e. the respiratory chain.

Answer: b

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

Bloom’s Category: 1. Remembering

19. In steps 6 through 10 of glycolysis, the conversion of 1 mole of glyceraldehyde 3-phosphate to pyruvate yields 2 moles of ATP. But the oxidation of glucose to pyruvate produces a total of 4 moles of ATP. Where do the remaining 2 moles of ATP come from?

a. One mole of glucose yields 2 moles of glyceraldehyde 3-phosphate.

b. Two moles of ATP are used during the conversion of glucose to glyceraldehyde 3-phosphate.

c. Glycolysis produces 2 moles of NADH.

d. Fermentation of pyruvate to lactic acid yields 2 moles of ATP.

e. Fermentation of pyruvate to lactic acid yields 2 moles of NAD+.

Answer: a

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

Bloom’s Category: 4. Analyzing

20. The end product of glycolysis is

a. pyruvate.

b. the starting point for pyruvate oxidation.

c. the starting point for the fermentation pathway.

d. Both a and b

e. All of the above

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

21. In the first reaction of glycolysis, glucose receives a phosphate group from ATP. This reaction is

a. respiration.

b. a redox reaction.

c. exergonic.

d. endergonic.

e. fermentation.

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

22. For glucose to be used as an energy source, it is necessary that

a. glucose be formed from fructose.

b. glucose phosphate be formed from fructose phosphate.

c. glucose be degraded to carbon dioxide.

d. two ATP molecules be invested in the system.

e. None of the above

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

23. ATP is used to drive the first five reactions of glycolysis because

a. nonspontaneous reactions are exergonic.

b. the breakdown of ATP to ADP is exergonic.

c. the breakdown of ATP to ADP is endergonic.

d. when ATP is broken down to ADP, Pi is released.

e. ADP possesses more free energy than ATP does.

Answer: b

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

24. The first five reactions of the glycolytic pathway result in

a. the addition of phosphates, modification of sugars, and formation of G3P.

b. oxidative steps, proton pumping, and reactions with oxygen.

c. the oxidation of pyruvate and formation of acetyl CoA.

d. the removal of hydrogen and protons from glucose.

e. None of the above

Answer: a

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

25. The free energy released during the oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate is

a. used to oxidize NADH.

b. lost as heat.

c. used to synthesize ATP.

d. used to reduce NAD+.

e. stored in lactic acid.

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

26. The end result of glycolysis is the

a. creation of 38 molecules of ATP.

b. reduction of 8 molecules of NAD.

c. formation of 2 molecules of pyruvate.

d. conversion of 1 molecule of glucose to lactic acid.

e. None of the above

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 1. Remembering

27. Within the cell, the pyruvate dehydrogenase complex, a multienzyme complex of the citric acid cycle, is located in the

a. thylakoids.

b. cytoplasm.

c. chloroplast.

d. mitochondrial matrix.

e. plasma membrane.

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 1. Remembering

28. Substrate-level phosphorylation is the transfer of a(n)

a. phosphate to a protein.

b. phosphate to a substrate.

c. phosphate to an ADP.

d. ATP to a protein.

e. phosphate from ATP to a substrate.

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 1. Remembering

29. Some of the free energy released by oxidation of pyruvate to acetate is stored in acetyl CoA. How does acetyl CoA store free energy?

a. Acetyl CoA has a higher free energy than acetate.

b. Acetyl CoA is an electron carrier.

c. Acetyl CoA is a phosphate donor.

d. Acetate + CoA → acetyl CoA is an exergonic reaction.

e. Reduction of acetyl CoA is coupled to ATP synthesis.

Answer: a

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 2. Understanding

30. During glycolysis, for each mole of glucose oxidized to pyruvate,

a. 6 moles of ATP are produced.

b. 2 moles of ATP are produced.

c. 4 moles of ATP are produced.

d. 2 moles of NAD+ are produced.

e. no ATP is produced.

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 3. Applying

31. Which process converts glucose to pyruvate, generating a small amount of ATP but no carbon dioxide?

a. Pyruvate oxidation

b. Glycolysis

c. The citric acid cycle

d. Respiratory chain

e. Gluconeogenesis

Answer: b

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 1. Remembering

32. Pyruvate oxidation generates

a. acetate.

b. NADH + H+ from NAD+.

c. a change in free energy.

d. CO2.

e. All of the above

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 1. Remembering

33. During the citric acid cycle, energy stored in acetyl CoA is used to

a. create a proton gradient.

b. drive the reaction ADP + Pi → ATP.

c. reduce NAD+ to NADH.

d. drive the reaction oxaloacetate → citric acid.

e. reduce FAD to FADH2.

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 2. Understanding

34. The citric acid cycle begins with

a. glucose.

b. pyruvate.

c. acetyl CoA.

d. NADH + H+.

e. ATP synthase.

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 1. Remembering

35. During the citric acid cycle, oxidative steps are coupled to

a. oxidative phosphorylation.

b. the oxidation of water.

c. the oxidation of electron carriers.

d. the hydrolysis of ATP.

e. the reduction of electron carriers.

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 2. Understanding

36. More free energy is released during the citric acid cycle than during glycolysis, but only 1 mole of ATP is produced for each mole of acetyl CoA that enters the cycle. Most of the remaining free energy produced during the citric acid cycle is

a. used to synthesize GTP.

b. used to reduce electron carriers.

c. lost as heat.

d. used to reduce pyruvate.

e. converted to kinetic energy.

Answer: b

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 4. Analyzing

37. For the citric acid cycle to proceed, it is necessary for

a. pyruvate to bind to oxaloacetate.

b. carbon dioxide to bind to oxaloacetate.

c. an acetyl group to bind to oxaloacetate.

d. water to be oxidized.

e. None of the above

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 176

Bloom’s Category: 2. Understanding

38. Which of the following is produced during the citric acid cycle?

a. FAD

b. Pyruvate

c. Reduced electron carriers

d. Lactic acid

e. Water

Answer: c

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 177

Bloom’s Category: 2. Understanding

39. Animals breathe in air containing oxygen and breathe out air with less oxygen and more carbon dioxide. The carbon dioxide comes from

a. hydrocarbons and the air.

b. the citric acid cycle.

c. glycolysis.

d. waste products.

e. All of the above

Answer: b

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 177

Bloom’s Category: 2. Understanding

40. How does the reduction of pyruvate to lactic acid during fermentation allow glycolysis to continue in the absence of oxygen?

a. Water is formed during this reaction.

b. This reaction is a kinase reaction.

c. This reaction is coupled to the oxidation of NADH to NAD+.

d. This reaction is coupled to the formation of ATP.

e. This reaction is coupled to the reduction of NAD+ to NADH.

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 177

Bloom’s Category: 2. Understanding

41. Which of the following statements about the electron transport chain is true?

a. Electrons are received from NADH and FADH2.

b. Electrons are passed from donor to recipient carrier molecules in a series of oxidation–reduction reactions.

c. Usually the terminal electron acceptor is oxygen.

d. Most of the enzymes are part of the inner mitochondrial membrane.

e. All of the above

Answer: e

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 4. Analyzing

42. The electron transport chain contains four large protein complexes: NADH-Q reductase complex, succinate dehydrogenase, cytochrome c reductase complex, and cytochrome c oxidase complex. These proteins

a. are integral proteins.

b. change in a similar way when reduced.

c. regulate the passage of water through the respiratory chain.

d. oxidize NADH.

e. complete oxidation of pyruvate to acetate.

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 1. Remembering

43. Animals inhale air containing oxygen and exhale air with less oxygen and more carbon dioxide. After inhalation, the oxygen missing from the air will mostly be found in

a. the carbon dioxide that is exhaled.

b. water.

c. organic molecules.

d. ethanol.

e. lactate.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 2. Understanding

44. Electron transport within NADH-Q reductase, cytochrome reductase, and cytochrome oxidase can be coupled to proton transport from the mitochondrial matrix to the space between the inner and outer mitochondrial membranes, because those protein complexes are

a. in the mitochondrial matrix.

b. within the inner mitochondrial membrane.

c. in the space between the inner and outer mitochondrial membranes.

d. in the cytoplasm.

e. loosely attached to the inner mitochondrial membrane.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 1. Remembering

45. Water is a by-product of cellular respiration. The water is produced as a result of the

a. combining of carbon dioxide with protons.

b. conversion of pyruvate to acetyl CoA.

c. degradation of glucose to pyruvate.

d. reduction of oxygen at the end of the electron transport chain.

e. None of the above

Answer: d

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 2. Understanding

46. The oxidizing agent at the end of the electron transport chain is

a. O2.

b. NAD+.

c. ATP.

d. FAD.

e. ubiquinone.

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 2. Understanding

47. Which of the following events occurs in the electron transport chain?

a. CO2 is released.

b. CO2 is reduced.

c. Cytochromes, FADH, and NADH are oxidized.

d. Only NAD+ is reduced.

e. None of the above

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 1. Remembering

48. The electron transport chain contains four large protein complexes (I, II, III, and IV), cytochrome c, and ubiquinone. The function of these molecules is to

a. transport electrons.

b. ensure the production of water and oxygen.

c. regulate the passage of water through the chain.

d. oxidize NADH.

e. None of the above

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 2. Understanding

49. The drug 2,4-dinitrophenol (DNP) destroys the proton gradient across the inner mitochondrial membrane. What would be the effect of incubating isolated mitochondria in a solution of DNP?

a. Oxygen would no longer be reduced to water.

b. No ATP would be made during transport of electrons down the respiratory chain.

c. Mitochondria would show a burst of increased ATP synthesis.

d. Glycolysis would stop.

e. Mitochondria would switch from glycolysis to fermentation.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

Bloom’s Category: 3. Applying

50. The hydrogen ion gradient is maintained by

a. electron transport and proton pumping.

b. the splitting of water.

c. the ionization of glucose.

d. ATP synthase.

e. acetyl CoA.

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

Bloom’s Category: 2. Understanding

51. When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane into the intermembranous space, the result is the

a. formation of ATP.

b. reduction of NAD+.

c. creation of a proton gradient.

d. restoration of the Na+–K+ balance across the membrane.

e. reduction of glucose to lactic acid.

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

Bloom’s Category: 2. Understanding

52. The chemiosmotic generation of ATP is driven by

a. osmotic movement of water into an area of high solute concentration.

b. the addition of protons to ADP and phosphate via enzymes.

c. oxidative phosphorylation.

d. the proton-motive force.

e. isocitrate dehydrogenase.

Answer: d

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

Bloom’s Category: 2. Understanding

53. The component of aerobic respiration that produces the most ATP per mole of glucose is

a. the electron transport chain.

b. the citric acid cycle.

c. glycolysis.

d. lactic acid fermentation.

e. alcoholic fermentation.

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

Bloom’s Category: 2. Understanding

54. According to the chemiosmotic theory, the energy for the synthesis of ATP during the flow of electrons down the respiratory chain is provided directly by the

a. hydrolysis of GTP.

b. reduction of NAD+.

c. diffusion of protons.

d. reduction of FAD.

e. hydrolysis of ATP.

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 180

Bloom’s Category: 2. Understanding

55. The proton-motive force is

a. ATP synthase.

b. the proton concentration gradient and electric charge difference.

c. a metabolic pathway.

d. a redox reaction.

e. None of the above

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 180

Bloom’s Category: 1. Remembering

56. In some mammals, such as newborn humans and hibernating animals, body temperature is raised by means of

a. the uncoupling of respiration by the protein thermogenin.

b. an increase in the rate of glycolysis.

c. shivering.

d. leakage of hydrogen ions across the cell’s plasma membrane.

e. cytochrome reductase.

Answer: a

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 181

Bloom’s Category: 1. Remembering

57. Oxygen is used by

a. glycolysis.

b. the citric acid cycle.

c. the electron transport chain.

d. substrate-level phosphorylation.

e. ATP synthase.

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 181

Bloom’s Category: 1. Remembering

58. The formation of ethanol from pyruvate is an example of

a. an exergonic reaction.

b. an extra source of energy as the result of glycolysis.

c. a fermentation process that takes place in the absence of oxygen.

d. cellular respiration.

e. None of the above

Answer: c

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 181

Bloom’s Category: 2. Understanding

59. Most ATP produced in our bodies is made

a. by glycolysis.

b. in the citric acid cycle.

c. using ATP synthase.

d. from photosynthesis.

e. by burning fat.

Answer: c

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 181

Bloom’s Category: 2. Understanding

60. Regardless of the electron or hydrogen acceptor employed, fermentation always produces

a. AMP.

b. DNA.

c. Pi.

d. NAD+.

e. None of the above

Answer: d

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

61. In the absence of oxygen, cells capable of fermentation

a. accumulate glucose.

b. no longer produce ATP.

c. accumulate pyruvate.

d. oxidize FAD.

e. oxidize NADH to produce NAD+.

Answer: e

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

62. For bacteria to continue growing rapidly when they are shifted from an environment containing oxygen to an anaerobic environment, they must

a. increase the rate of the citric acid cycle.

b. produce more ATP per mole of glucose during glycolysis.

c. produce ATP during the oxidation of NADH.

d. increase the rate of transport of electrons down the respiratory chain.

e. increase the rate of the glycolytic reactions.

Answer: e

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

63. In human muscle cells, the fermentation process produces

a. lactic acid.

b. 12 moles of ATP.

c. pyruvic acid.

d. an excessive amount of energy.

e. None of the above

Answer: a

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 1. Remembering

64. In alcoholic fermentation, NAD+ is produced during the

a. oxidation of pyruvate to acetyl CoA.

b. reduction of pyruvate to lactic acid.

c. reduction of acetaldehyde to ethanol.

d. hydrolysis of ATP to ADP.

e. oxidation of glucose.

Answer: c

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

65. During the fermentation of one molecule of glucose, the net production of ATP is _______ molecule(s).

a. one

b. two

c. three

d. six

e. eight

Answer: b

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

66. Many species derive their energy from fermentation. The function of fermentation is to

a. reduce NAD+.

b. oxidize CO2.

c. oxidize NADH + H+, ensuring a continued supply of ATP.

d. produce acetyl CoA.

e. None of the above

Answer: c

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

67. Yeast cells tend to create anaerobic conditions because they use oxygen more quickly than it can be replaced by diffusion through the cell membrane. For this reason, yeast cells

a. exhibit a red pigment.

b. exhibit a green pigment.

c. die.

d. produce ethanol.

e. None of the above

Answer: d

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

68. Before starch can be used for respiratory ATP production, it must be hydrolyzed to

a. pyruvate.

b. fatty acids.

c. amino acids.

d. glucose.

e. oxaloacetate.

Answer: d

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

Bloom’s Category: 1. Remembering

69. When acetyl CoA builds up in the cell, it increases the activity of the enzyme that synthesizes oxaloacetate from pyruvate and carbon dioxide. Acetyl CoA is acting as a(n)

a. electron carrier.

b. substrate.

c. allosteric activator.

d. acetate donor.

e. proton pump.

Answer: c

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 1. Remembering

70. Fats are the preferred energy source in many organisms because

a. they are less dense than polysaccharides.

b. they have more C—H bonds and less C—OH bonds.

c. they are nonpolar.

d. fats do not bind to water.

e. they have essential roles as enzymes and structural elements.

Answer: b

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 4. Analyzing

71. A person on a severe diet will lose weight but is also likely to suffer from undernutrition and eventually starvation. If a person does not eat enough to produce sufficient ATP and NADH for biological activities, energy sources will be depleted in what order?

a. Glycogen; fats; proteins

b. Fats; glycogen; proteins

c. Glycogen; proteins; fats

d. Fats; proteins; glycogen

e. Proteins; glycogen; fats

Answer: a

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 2. Understanding

72. When a cell needs energy, cellular respiration is regulated by isocitrate dehydrogenase, an enzyme of the citric acid cycle. This enzyme is stimulated by

a. H+.

b. heat.

c. oxygen.

d. ADP.

e. None of the above

Answer: d

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 1. Remembering

73. The main control mechanism in glycolysis is the

a. enzyme isocitrate dehydrogenase.

b. negative feedback of citrate accumulation.

c. presence or absence of oxygen.

d. enzyme phosphofructokinase.

e. supply of NAD.

Answer: d

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 1. Remembering

74. In yeast, if the citric acid cycle is shut down because of a lack of oxygen, glycolysis will probably

a. shut down.

b. increase.

c. produce more ATP per mole of glucose.

d. produce more NADH per mole of glucose.

e. produce acetyl CoA for fatty acid synthesis.

Answer: b

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 3. Applying

75. When the supply of acetyl CoA being produced exceeds the demands of the citric acid cycle, some of the acetyl CoA is diverted to the synthesis of

a. pyruvate.

b. NAD.

c. proteins.

d. fatty acids.

e. lactic acid.

Answer: d

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 2. Understanding

76. If a cell has an abundant supply of ATP, acetyl CoA may be used

a. to enhance fermentation.

b. to enhance oxidative metabolism.

c. for fatty acid synthesis.

d. to convert glucose to glycogen.

e. None of the above

Answer: c

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 185

Bloom’s Category: 1. Remembering

77. When yeast cells are switched from aerobic to anaerobic growth conditions, the rate of glycolysis increases. The rate of glycolysis is regulated by the concentration of _______ in the cells.

a. ATP

b. acetyl CoA

c. oxaloacetate

d. FAD

e. protein

Answer: a

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 186

Bloom’s Category: 2. Understanding

Fill in the Blank

1. Muscle cells of marathon racers contain many mitochondria and use oxygen to break down fats and carbohydrates. Ninety percent of marathon runners’ muscle is made up of _______.

Answer: slow-twitch fibers

Textbook Reference: 9.0 Of mice and marathons

Page: 168

Bloom’s Category: 1. Remembering

2. _______ is a protein receptor that regulates the transcription of genes involved in the breakdown of fat into ATP.

Answer: PPARδ

Textbook Reference: 9.0 Of mice and marathons

Page: 168

Bloom’s Category: 1. Remembering

3. In nonphotosynthetic organisms, the most common chemical fuel is _______.

Answer: glucose

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 169

Bloom’s Category: 1. Remembering

4. A chemical reaction resulting in the transfer of electrons or hydrogen atoms is called a(n) _______ reaction.

Answer: redox

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 169

Bloom’s Category: 1. Remembering

5. Oxidation and _______ occur together.

Answer: reduction

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 2. Understanding

6. Fermentation occurs in the absence of oxygen and is therefore termed _______.

Answer: anaerobic

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 1. Remembering

7. The loss of an electron by a ferrous ion (Fe2+) to yield a ferric ion (Fe3+) is called _______.

Answer: oxidation

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 2. Understanding

8. In a redox reaction, the reactant that becomes oxidized is called a(n) _______.

Answer: reducing agent

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

Bloom’s Category: 1. Remembering

9. Due to its ability to carry electrons and free energy, _______ is the most common electron carrier in cells.

Answer: NAD

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 1. Remembering

10. The abbreviation for nicotinamide adenine dinucleotide is _______.

Answer: NAD

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 171

Bloom’s Category: 1. Remembering

11. The pathway for the oxidation of glucose to pyruvate is called _______.

Answer: glycolysis

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 172

Bloom’s Category: 1. Remembering

12. The enzyme-catalyzed transfer of phosphate groups to ADP molecules to form ATP is called _______.

Answer: substrate-level phosphorylation

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 174

Bloom’s Category: 1. Remembering

13. Pyruvate is _______ to form acetate.

Answer: oxidized

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 1. Remembering

14. The oxidation of citrate to carbon dioxide is known as the _______.

Answer: citric acid cycle

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175

Bloom’s Category: 1. Remembering

15. The chemiosmotic formation of ATP during the operation of the respiratory chain is called _______.

Answer: oxidative phosphorylation

Textbook Reference: 9.3 How Does the Oxidation Phosphorylation Form ATP?

Page: 177

Bloom’s Category: 1. Remembering

16. The passing of electrons through a series of protein molecules is called the _______.

Answer: electron transport chain

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 1. Remembering

17. The conversion of glucose to lactic acid is a form of _______.

Answer: fermentation

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 2. Understanding

18. During alcoholic fermentation, NAD+ is regenerated by the reduction of acetaldehyde to _______.

Answer: ethanol

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 1. Remembering

19. Fatty acids must be converted to _______ before they can be used for respiratory ATP production.

Answer: acetyl CoA

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

Bloom’s Category: 1. Remembering

20. The formation of glucose from glycolytic and citric acid intermediates is called _______.

Answer: gluconeogenesis

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 186

Bloom’s Category: 1. Remembering

Diagram

1. Refer to the diagram below. The source of electrons for the electron transport chain is

[pic]

a. FADH2.

b. NADH-Q reductase complex.

c. NADH + H+.

d. ubiquinone.

e. Both a and c

Answer: e

Textbook Reference: 9.3 How Does the Oxidation Phosphorylation Form ATP?

Page: 178

Bloom’s Category: 2. Understanding

STUDY GUIDE QUESTIONS

(By Jacalyn Newman)

Knowledge and Synthesis

1. Which of the following cellular metabolic processes is active in all cells, regardless of the presence or the absence of oxygen?

a. The citric acid cycle

b. Electron transport

c. Glycolysis

d. Fermentation

e. Pyruvate oxidation

Answer: c

Feedback: Glycolysis proceeds during both fermentation and cellular respiration. Only in cellular respiration is oxygen needed as the terminal electron acceptor of the pathway.

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

2. Which of the following statements regarding glycolysis is false?

a. A 6-C sugar is broken down to two 3-C molecules.

b. Two ATP molecules are consumed.

c. Glycolysis requires oxygen.

d. A net sum of two ATP molecules is generated.

e. Glycolysis occurs in the cytosol.

Answer: c

Feedback: During glycolysis, 6-C glucose is broken down into two 3-C pyruvate molecules. In the process, four total ATP are produced, but two are consumed, leaving a net production of two ATP molecules. No oxygen is required in glycolysis.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

3. During which process is most ATP generated in the cell?

a. Glycolysis

b. The citric acid cycle

c. Electron transport coupled with chemiosmosis

d. Fermentation

e. Pyruvate oxidation

Answer: c

Feedback: Most of the ATP produced during cellular respiration is produced by electron transport and chemiosmosis coupled in oxidative phosphorylation.

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 183

4. One purpose of the electron transport chain is to

a. cycle NADH + H+ back to NAD+.

b. use the intermediates from the citric acid cycle.

c. break down pyruvate.

d. increase the number of protons in the mitochondrial matrix.

e. consume excess ATP.

Answer: a

Feedback: The electron transport chain is responsible for oxidizing NADH + H+ back to NAD+.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178

5. Cellular respiration is allosterically controlled. Which of the following act(s) as inhibitors at the various control points?

a. ATP

b. NADH

c. Both ATP and NADH

d. ADP

e. Both ADP and NADH

Answer: c

Feedback: Both ATP and NADH allosterically control metabolism. ATP controls both phosphofructokinase and isocitrate dehydrogenase, which are commitment steps for glycolysis and the citric acid cycle, respectively. NADH controls isocitrate dehydrogenase.

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 186

6. Which of the following describes the role of the inner mitochondrial membrane?

a. It acts as an anchor for the membrane-associated enzymes of cellular respiration.

b. It allows for the establishment of a proton gradient.

c. It separates the mitocondria’s environment from that of the cytosol.

d. It anchors enzymes and allows for the establishment of the proton gradient, but it is not involved in separating the contents of the mitochondria from the cytosol.

e. It anchors enzymes, allows for the establishment of the proton gradient, and is involved in separating the contents of the mitochondria from the cytosol.

Answer: c

Feedback: The mitochondrial membrane is necessary for the anchoring of proteins as well as the establishment of a barrier across which a gradient can be established.

Textbook Reference: 9.3 How Does the Oxidative Phosphorylation Form ATP?

Page: 179, Figure 9.9

7. In the following redox reaction, _______ is oxidized and _______ is reduced.

Glyceraldehyde 3-phosphate (G3P) + NAD+ + H+ + Pi → 1,3-Bisphosphoglycerate (BPG) + NADH

a. G3P; NAD+

b. BPG; NADH + H+

c. G3P; NADH + H+

d. NAD+; NADH + H+

e. The equation does not show a redox reaction.

Answer: a

Feedback: A molecule is oxidized when it loses electrons or protons and is reduced when it gains electrons or protons. In this reaction, G3P donates electrons and therefore is oxidized, while NAD+ accepts them and thus is reduced.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

8. Which of the following statements about redox reactions is true?

a. Oxidizing agents accept electrons.

b. Oxidizing agents donate electrons.

c. A molecule that accepts electrons is said to be oxidized.

d. A molecule that donates electrons is said to be reduced.

e. Oxidizing agents accept electrons and are reduced in the process.

Answer: e

Feedback: Oxidizing agents accept electrons and cause oxidation of another molecule. Reducing agents donate electrons and cause the reduction of another molecule.

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

9. Cyanide poisoning inhibits aerobic respiration at cytochrome c oxidase. Which of the following is not a result of cyanide poisoning at the cellular level?

a. Reduction of oxygen to water

b. Cessation of ATP synthesis in the mitochondria because electron transport is never completed

c. Switching of cells to anaerobic respiration and fermentation if possible

d. Continuation of glycolysis as long as NAD+ is available

e. Less acidic pH of the intermenbrane space

Answer: a

Feedback: Cyanide stops aerobic cellular respiration because cytochrome c oxidase loses the ability to reduce oxygen to water. Those cells that can switch to anaerobic respiration (fermentation) do so and use their remaining glucose more quickly. Cells that cannot make that switch die.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

10. Which of the following is correctly matched with its catabolic product?

a. polysaccharides → amino acids

b. lipids → glycerol and fatty acids

c. proteins → glucose

d. polysaccharides → glycerol and fatty acids

e. nucleic acids → monosaccharides

Answer: b

Feedback: Lipids are broken down into glycerol and fatty acids; polysaccharides are broken down into glucose; proteins are broken down into amino acids. Nucleic acids are converted into some amino acids and fed into the citric acid cycle.

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

11. The main function of cellular respiration is the

a. conversion of energy stored in the chemical bonds of glucose to an energy form that the cell can use.

b. recovery of NAD+ from NADPH.

c. conversion of kinetic to potential energy.

d. creation of energy in the cell.

e. elimination of excess glucose from the cell.

Answer: a

Feedback: Cellular respiration is the cell’s way of converting potential energy in the chemical bonds of glucose to potential energy that the cell ultimately can use.

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170

12. Which of the following statements concerning the synthesis of ATP in the mitochondria is false?

a. ATP synthesis cannot occur without the presence of ATP synthase.

b. The proton-motive force is the establishment of a charge and concentration gradient across the mitochondrial membrane.

c. The proton-motive force drives protons back across the membrane through channels established by the ATP synthase channel protein.

d. The ATP synthase protein is composed of two units.

e. The intermembrane space is more basic than the mitochondrial matrix.

Answer: a

Feedback: Substrate level phosphorylation occurs in step 5 of the citric acid cycle in the mitochondria. The intermembrane space is more acidic than the matrix.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

13. Which of the following does not occur in the mitochondria of eukaryotic cells?

a. Fermentation

b. Oxidative phosphorylation

c. Citric acid cycle

d. Electron transport chain

e. Creation of a proton gradient

Answer: a

Feedback: Fermentation occurs in the cytosol, whereas all the other processes occur in the mitochondria of eukaryotic cells.

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 172

14. The largest change in free energy during glycolysis occurs at which reaction?

a. Reaction 2: G6P → F6P

b. Reaction 5: DAP → G3P

c. Reaction 6: G3P → BPG + NADH

d. Reaction 7: BPG → 3PG + ATP

e. Reaction 8: 3PG → 2PG

Answer: c

Feedback: The largest change in free energy occurs in reaction 6, with more than 100 kcal/mol released.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173

15. Which of the following is recycled and reused in cellular metabolism?

a. ADP

b. NAD+

c. FAD

d. Pi

e. All of the above

Answer: e

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 172–173

16. For each molecule of glucose, how many ATPs are synthesized in fermentation?

a. 0

b. 1

c. 2

d. 3

e. 4

Answer: a

Feedback: ADP, NAD+, FAD, and Pi are all recycled and reused in the process of cellular respiration.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 172–173

17. If additional malate is added to a cell undergoing cellular respiration, there will be

a. an increase in CO2 production but no increase in ATP synthesis.

b. an increase in CO2 production and a decrease in ATP synthesis.

c. an increase in both the CO2 production and ATP synthesis.

d. a decrease in both the CO2 production and ATP synthesis.

e. no change in the rates of CO2 production or ATP synthesis.

Answer: c

Feedback: Additional malate will increase the carbon compounds cycling through the citric acid cycle, resulting in an increase in the products of the citric acid cycle, including ATP and CO2.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 176–177

Application

1. Why is oxygen necessary for aerobic respiration?

Answer: Oxygen acts as the terminal electron acceptor in the electron transport pathway. Without it, NADH + H+ cannot be cycled back to NAD+. The accumulated NADH + H+ acts as an inhibitor to the citric acid cycle and effectively shuts it down. Therefore, in the absence of oxygen, a cell can only undergo glycolysis.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 177

2. Glycolysis yields two molecules of pyruvate, two ATP, and two NADH + H+, regardless of whether oxygen is present or not. What are the fates of these molecules in the absence of oxygen? What would happen if NADH + H+ was not recycled?

Answer: In the absence of oxygen, pyruvate is either reduced to lactate (in lactic acid fermentation) or it is metabolized and its metabolites are reduced to ethyl alcohol (in alcoholic fermentation). In either case, NADH + H+ is the reducing agent, and it is oxidized back to NAD+ in the process. The two molecules of ATP would be used as cellular energy. If NADH + H+ was not oxidized to NAD+, there would eventually be no NAD+ available for glycolysis.

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 181–182

3. Explain how the proton-motive force drives chemiosmosis.

Answer: The proton-motive force results in a concentration and charge gradient across the mitochondrial membrane. For that gradient to equalize, the protons must flow through a channel protein. If this channel protein has an associated ATP synthase, ATP is generated as protons flow through.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 179

4. The fate of acetyl CoA differs according to how much ATP is present in the cell. Explain what happens to acetyl CoA when ATP is limited, and compare that to what happens when acetyl CoA is abundant. How do these processes help regulate metabolism?

Answer: If ATP is limited, acetyl CoA enters the citric acid cycle, and cellular respiration utilizes it to produce ATP. If ATP is abundant, acetyl CoA is shuttled to fatty acid synthesis, thus storing the energy in chemical bonds.

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

5. Cellular respiration occurs simultaneously with many other cellular processes. Describe, in general, how cellular respiration interacts with other cellular metabolic events.

Answer: Consult Figure 9.14 to see where different metabolic pathways in the cell interact.

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

6. Compare and contrast energy yields from aerobic respiration and fermentation.

Answer: a

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

7. One of the by-products of aerobic cellular respiration is carbon dioxide. Assuming you begin with labeled glucose, trace the fate of that molecule until carbon dioxide is released.

Answer: Fermentation yields only two ATP. Cellular respiration yields 32 ATP.

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173, 176

8. Identify the controlling steps of glycolysis, the citric acid cycle, and electron transport. Which regulators affect each of these steps?

Answer: This control point for glycolysis is phosphofructo-kinase, which is inhibited by ATP. This allows glycolysis to speed up during fermentation and slow down during cellular respiration. The control point for the citric acid cycle is isocitrate dehydrogenase. NADH + H+ and ATP inhibit the enzyme, and NAD+ and ADP are activators. Electron transport is controlled by the amount of NADH + H+ fed in and by NADH-Q reductase.

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 186

9. Cyanide kills by inhibiting cytochrome oxidase in the mitochondria so that oxygen can no longer be utilized and the electron transport chain halts. However, many cells in the human body are capable of lactic acid fermentation. Since cyanide does not inhibit glycolysis and fermentation, what could explain cyanide’s lethal affect on humans?

Answer: Based on what you have learned in this chapter, you should be thinking about the reduced efficiency of glycolysis and fermentation for ATP synthesis, which is one reason why oxygen deprivation is so deadly to humans. (And, as later chapters will show, the resulting lactic acid buildup also causes problems.) In addition, not all cells are capable of carrying out the reactions of fermentation. Brain cells, for example, will simply die in the absence of oxygen.

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 181

10. Where do the bubbles in beer come from?

Answer: The bubbles in beer are bubbles of CO2 released during the fermentation of pyruvate into ethyl alcohol. See Figure 9.12.

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

11. When a person consumes a packet of pure sugar and burns it for energy, where does the carbon in the sugar ultimately go? Is the same true of the carbons in fat molecules when a person loses weight?

Answer: The carbon in the sugar is exhaled in the form of CO2. When someone loses weight, the carbon from the fat molecules is also exhaled in the form of CO2.

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 176

TEXTBOOK SELF-QUIZ

1. The role of oxygen gas in our cells is to

a. catalyze reactions in glycolysis.

b. produce CO2.

c. form ATP.

d. accept electrons from the respiratory chain.

e. react with glucose to split water.

Answer: d

2. Oxidation and reduction

a. entail the gain or loss of proteins.

b. are defined as the loss of electrons.

c. are both endergonic reactions.

d. always occur together.

e. proceed only under aerobic conditions.

Answer: d

3. NAD+ is

a. a type of organelle.

b. a protein.

c. present only in mitochondria.

d. a part of ATP.

e. formed in the reaction that produces ethanol.

Answer: e

4. Glycolysis

a. takes place in the mitochondrion.

b. produces no ATP.

c. has no connection with the respiratory chain.

d. is the same thing as fermentation.

e. reduces two molecules of NAD+ for every glucose molecule processed.

Answer: e

5. Fermentation

a. takes place in the mitochondrion.

b. takes place in all animal cells.

c. does not require O2.

d. requires lactic acid.

e. prevents glycolysis.

Answer: c

6. Which statement about pyruvate is not true?

a. It is the end product of glycolysis.

b. It becomes reduced during fermentation.

c. It is a precursor of acetyl CoA.

d. It is a protein.

e. It contains three carbon atoms.

Answer: d

7. The citric acid cycle

a. has no connection with the respiratory chain.

b. is the same thing as fermentation.

c. reduces two NAD+ for every glucose processed.

d. produces no ATP.

e. takes place in the mitochondrion.

Answer: e

8. The respiratory chain

a. is located in the mitochondrial matrix.

b. includes only peripheral membrane proteins.

c. always produces ATP.

d. reoxidizes reduced coenzymes.

e. operates simultaneously with fermentation.

Answer: d

9. Compared with fermentation, the aerobic pathways of glucose metabolism produce

a. more ATP.

b. pyruvate.

c. fewer protons for pumping in the mitochondria.

d. less CO2.

e. more oxidized coenzymes.

Answer: a

10. Which statement about oxidative phosphorylation is not true?

a. It forms ATP by the respiratory chain/ATP synthesis.

b. It is brought about by chemiosmosis.

c. It requires aerobic conditions.

d. It takes place in mitochondria.

e. Its functions can be served equally well by fermentation.

Answer: e

BIOPORTAL DIAGNOSTIC QUIZ (Personalized Study Plan Quiz)

(By Richard McCarty)

1. Which one of the following reactions is not an oxidation–reduction reaction?

a. NADH + ½O2 + H+ ↔ NAD+ + H2O

b. R—CH=CH—CH3 + H2O ↔ RCH2—CH(OH)—CH3

c. FAD + H2O ↔ FADH2 + ½O2

d. NADH + acetaldehyde ↔ NAD+ + ethanol

e. AH2 + B ↔ A +BH2

Answer: b

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170–171

Bloom’s Category: 2. Understanding

2. Glycolysis

a. is the conversion of glucose to two molecules of lactate.

b. is an endergonic reaction.

c. consumes ATP.

d. is an oxidation–reduction process.

e. releases carbon dioxide.

Answer: d

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170–171

Bloom’s Category: 2. Understanding

14. The conversion of malate to oxaloacetate in the citric acid cycle takes place with the conversion of NAD+ to NADH. In this reaction, NAD+ is

a. the reducing agent.

b. the oxidizing agent.

c. reduced.

d. oxidized.

e. Both b and c

Textbook Reference: 9.1 How Does Glucose Oxidation Release Chemical Energy?

Page: 170–171

Bloom’s Category: 2. Understanding

4. The end products of glycolysis are

a. pyruvate.

b. pyruvate, ATP, and NAD+.

c. acetylCoA, ATP, and NAD+.

d. pyruvate, ATP, and NADH.

e. acetylCoA, ATP, and NADH.

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173–174

Bloom’s Category: 2. Understanding

5. In the complete oxidation of glucose, 6 CO2 molecules are formed per glucose oxidized. Choose from the list below the correct numbers of CO2 molecules released by glycolysis (gly), the citric acid cycle (CAC), and pyruvate oxidation (pyr).

a. gly 1; CAC 3; pyr 2

b. gly 2; CAC 2; pyr 2

c. gly 1; CAC 4; pyr 1

d. gly 0; CAC 4; pyr 2

e. gly 0; CAC 6; pyr 0

Answer: d

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 173–177

Bloom’s Category: 4. Analyzing

6. Which of the statements below about the citric acid cycle is false?

a. The cycle releases less energy than glycolysis.

b. CO2 is released during operation of the cycle.

c. The cycle takes place in the mitochondrial matrix.

d. The cycle requires NAD+ and FAD.

e. The cycle does not operate under anaerobic conditions.

Answer: a

Textbook Reference: 9.2 What Are the Aerobic Pathways of Glucose Metabolism?

Page: 175–177

Bloom’s Category: 4. Analyzing

7. Which of the compounds listed below link(s) glycolysis and the citric acid cycle to the mitochondrial electron transport chain?

a. NADH

b. ADP and Pi

c. FADH2

d. ATP

e. Both a and c

Answer: e

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 177–178

Bloom’s Category: 2. Understanding

8. The synthesis of ATP from ADP and Pi by mitochondria

a. is an oxidation–reduction reaction.

b. is linked to electron transport.

c. takes place in the absence of oxygen.

d. does not require energy.

e. accounts for a minor fraction of all of the ATP made by cells.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 177–179

Bloom’s Category: 2. Understanding

9. The mitochondrial electron transport chain

a. is the site of most of the reactions of the citric acid cycle.

b. synthesizes ATP.

c. pumps protons into the mitochondrial matrix during electron transport.

d. oxidizes the intermediate electron carriers, NADH and FADH2.

e. oxidizes water to O2 and 2 H+.

Answer: d

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 177–179

Bloom’s Category: 2. Understanding

10. The mitochondrial ATP synthase

a. is an entirely integral membrane protein.

b. couples the synthesis of ATP to the flow of protons across the inner membrane from inside to out.

c. is a soluble protein located in the mitochondrial matrix.

d. makes ATP at the expense of the proton gradient established by electron transport.

e. usually hydrolyzes ATP to establish a proton gradient.

Answer: d

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178–179

Bloom’s Category: 2. Understanding

11. The electron transport chain of mitochondria

a. is present in the outer membrane of the mitochondrion.

b. contains cytochromes and proteins containing flavins (FAD).

c. reduces NAD+.

d. generates an H+ gradient such that the outside of the mitochondrion is more basic than the inside.

e. makes ATP.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178–179

Bloom’s Category: 1. Remembering

12. The synthesis of ATP from ADP and Pi is an _______ reaction. In mitochondria, ATP synthesis is driven by the flow of _______ down the concentration and electrical gradient established by _______.

a. endergonic; Na+ ions; electron transport

b. exergonc; protons; glycolysis

c. endergonic; protons; electron transport

d. exergonic; Na+ ions; glycolysis

e. endergonic; protons; citric acid cycle

Answer: c

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 178–181

Bloom’s Category: 2. Understanding

13. Reagents, such as dinitrophenol, increase the permeability of the mitochondrial inner membrane to protons. The addition of dinitrophenol to a suspension of animal cells should

a. decrease the rate of oxidation of NADH.

b. inhibit mitochondrial ATP synthesis.

c. increase lactic acid production.

d. decrease the rate of pyruvate oxidation.

e. stimulate ATP synthesis by mitochondria.

Answer: b

Textbook Reference: 9.3 How Does Oxidative Phosphorylation Form ATP?

Page: 181

Bloom’s Category: 4. Analyzing

14. Fermentation

a. results in the formation of lactic acid or ethanol.

b. completely oxidizes glucose to CO2 and H2O.

c. is not coupled to ATP synthesis.

d. occurs under aerobic conditions in yeasts.

e. is endergonic.

Answer: a

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 181–182

Bloom’s Category: 2. Understanding

15. Cyanide inhibits the enzyme in the mitochondrial electron transport chain that reduces O2 to water. Suppose that you add cyanide to a suspension of muscle cells from a rat. Which statement given below is the most accurate with respect to the effects of cyanide on glucose catabolism?

a. The citric acid cycle and glycolysis would be inhibited.

b. The citric acid cycle would be inhibited, but glycolysis would not. Ethanol accumulates.

c. The citric acid cycle and glycolysis would be stimulated.

d. The citric acid cycle would be inhibited, but glycolysis would not. Lactic acid accumulates.

e. The citric acid cycle would not be inhibited, but glycolysis would.

Answer: d

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 4. Analyzing

16. What is the metabolic fate of pyruvate in anaerobic muscle?

a. It is converted to acetylCoA.

b. It is decarboxylated.

c. It is oxidized.

d. It is reduced to lactate.

e. It is converted to ethanol.

Answer: d

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182

Bloom’s Category: 1. Remembering

17. A suspension of yeast supplied with glucose as its source of energy was transferred from an aerobic environment to an anaerobic one. What do you think would happen to the rate of glucose utilization and the rate of ethanol production after the transfer?

a. Glucose usage would decrease; ethanol production would increase.

b. Glucose usage would increase; ethanol production would decrease.

c. Both glucose usage and ethanol production would increase.

d. Both glucose usage and ethanol production would be unchanged.

e. Glucose usage would not change; ethanol production would increase.

Answer: c

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182–183

Bloom’s Category: 3. Applying

18. Most of the ATP made during the complete oxidation of glucose to CO2 and water is

a. made by the mitochondrial ATP synthase.

b. from substrate-level phosphorylation.

c. synthesized by the sodium–potassium ATPase.

d. synthesized in the cytosol.

e. made directly by the citric acid cycle.

Answer: a

Textbook Reference: 9.4 How Is Energy Harvested from Glucose in the Absence of Oxygen?

Page: 182–183

Bloom’s Category: 2. Understanding

19. Triglycerides are major energy storage molecules. Which statement about the complete oxidation of triglycerides to CO2 and water and the oxidation of glucose to two molecules of pyruvate is correct?

a. They are both endergonic.

b. Both the complete oxidation of triglycerides and that of glucose to pyruvate use the citric acid cycle.

c. Acetyl CoA is an intermediate in the breakdown of both glucose to pyruvate and triglycerides.

d. Only glucose oxidation uses the glycolytic pathway.

e. Carbon dioxide is released by both pathways.

Answer: d

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184

Bloom’s Category: 4. Analyzing

20. Acetyl CoA

a. is formed within mitochondria by the reduction of pyruvate.

b. is formed within mitochondria by the oxidation of fatty acids.

c. is formed in the cytoplasm by the oxidation of glucose.

d. is used for the synthesis of sugars.

e. is formed in the cytosol during the complete oxidation of glucose.

Answer: e

Textbook Reference: 9.5 How Are Metabolic Pathways Interrelated and Regulated?

Page: 184–185

Bloom’s Category: 2. Understanding

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