BI0 120 cell and tissues



LESSON- 24

ENERGY METABOLISM: THE CHEMOORGANOTROPHS

RESPIRATION AND FERMENTATION

A. Objectives

— Explain the burden of energy production by chemoorganotrophs and suggest solutions.

— Explain the essence of fermentation and its need for or sensitivity to air; state what makes different fermentation pathways different; discuss the consequences of a fermentative metabolism; list some applications of fermentative pathways.

— Define respiration and compare to fermentation; explain the ATP production by electron transport phosphorylation; explain the proton motive force.

— Discuss energy yields of a fermenting and respiring organism; list advantages and disadvantages; give examples of fermenting and respiring organisms; locate the site of substrate-level and electron transport phosphorylation in the prokaryotic and eukaryotic cell.

B. Lecture outline

1. PROBLEM FACED BY CHEMOORGANOTROPHS

Read: The electron transport chain is coupled to ATP synthesis (SBM p179-185)

2. FERMENTATION

Read: Anaerobic respiration and fermentation (SBM p186-188)

a. fermentation pathway: general

b. variations on a theme

c. disadvantages, advantages

d. balance sheet

3. RESPIRATION

Read: Aerobic respiration of one glucose yields a maximum of 36 to 38 ATPs. (SBM p183-185)

a. mitochondrial electron tower

b. generation of a proton motive force

c. ATP synthesis

d. balance sheet

4. CARBOHYDRATE METABOLISM OF CHEMOHETEROTROPHS: C-heterotrophs

C. Study Question.

1. The reaction: C6H1206 + 6 O2 (6 Co2 + 6 H20, when it occurs in living cells is known as

A. fermentation.

B. anaerobic phosphorylation.

C. aerobic respiration.

D. glycolysis.

E. oxidative phosphorylation.

2. The reaction: C6H1206 + 6 02 (6 Co2 + 6 H20, when it occurs in living cells releases

A. energy in the form of 2 ATP molecules.

B. energy in the form of 6 Co2 molecules.

C. no energy in any form.

D. a total of 688 kcal per mole of glucose.

E. energy in the form of 38 ATP molecules.

3. The energy yield of (aerobic) respiration of glucose is about

A. 2%

B. 8%

C. 12%

D. 25%

E. 38%

4. The energy yield of fermentation of glucose to lactic acid is about

A. 2%

B. 8%

C. 12%

D. 25%

E. 38%

5. What statement summarizes best the fate of pyruvate?

A. respiration AND fermentation, usually both at the same time.

B. respiration OR fermentation, depending on the availability of primary electron donor and terminal electron acceptor.

C. respiration OR fermentation, depending on the complexity of the cell.

D. neither respiration NOR fermentation, except in a few rare bacteria.

E. respiration in eukaryotes, fermentation in prokaryotes.

6. Regardless of the nature of the terminal electron acceptor used, one of the products of fermentation is always

A. ADP.

B. ATP.

C. NAD+.

D. inorganic phosphate.

E. pyruvate.

7. Saccharomyces yeast cells create anaerobic conditions by using up oxygen faster than the gas can diffuse into the cells. The cells then

A. die.

B. produce oxygen from pyruvate.

C. ferment and produce ethanol.

D. run the glycolytic pathway backward to synthesize glucose.

E. switch to oxidative phosphorylat ion.

8. In muscle cells the product of fermentation is

A. ATP.

B. kinetic energy.

C. lactic acid.

D. NADH+H+.

E. pyruvate.

9. What happens to the oxygen that is used in (aerobic) respiration?

A. it is oxidized to form CO2.

B. it is recycled to accept more electrons.

C. it is reduces coenzyme I.

D. it is oxidized to water.

E. it is reduced to water.

10. What ions are pumped across the mitochondrial membrane when electrons pass along the electron transport system of the inner membrane?

A. e-.

B. Cl-.

C. K+.

D. H+.

E. Na+.

11. What acronym identifies an organic molecule that links acetate or succinate in an energy-rich molecule?

A. ATP.

B. FAD.

C. G3P.

D. NAD+.

E. CoA.

12. What acronym identifies the chief energy currency of cells?

A. ATP.

B. FAD.

C. G3P.

D. NAD+.

E. C0A.

13. What acronym identifies a dinucleotide, intermediate electron carrier that is only active in the Krebs cycle?

A. ATP.

B. FAD.

C. G3P.

D. NAD+.

E. CoA.

14. Which statement is TRUE for an electron transport system?

A. Reduced oxygen feeds electrons to the system.

B. The final electron acceptor is water.

C. Each electron carrier has the same affinity for electrons.

D. Electrons are finally accepted by a molecule with a negative reduction potential.

E. Electrons loose energy as they bounce down the steps of the membrane—bound electron tower.

15. When one molecule of glucose is degraded to carbon dioxide and water

A. 16 molecules of ATP are generated by substrate-level phosphorylation.

B. 38 molecules of ATP are synthesized by electrontransport phosphorylation.

C. 50% of the released energy is stored in ATP.

D. 8 molecules of NADH+H+ and 2 molecules of FADH2 are generated in the mitochondria.

E. water is oxidized to oxygen.

16. The final electron acceptor of aerobic respiration is

A. CO2.

B. O2.

C. H2O.

D. CoA.

E. NAD+

17. The oxygen which is the final electron acceptor in aerobic oxidative phosphorylation comes from

A. glucose.

B. water.

C. carbon dioxide.

D. air.

E. internal, organic molecule.

18. A respiring organism is given glucose that is radioactively labeled with 14C. After a few hours the radioactivity will be detected in the organism’s

A. H2O.

B. CoA.

C. membranes.

D. oxygen

E. carbon dioxide.

19. What condition(s) can be expected to inhibit cellular (aerobic) respiration?

A. lack of NAD+.

B. lack of oxygen.

C. lack of glucose.

D. excess of NADH+H+.

E. all of the above.

20. What reaction(s) would be minimally affected when tissue cells are grown ANAEROBICALLY.

A. glycolysis.

B. citric acid cycle.

C. electron transport phosphorylat ion.

D. breakdown of pyruvate to acetyl— coenzyme A.

E. reduction of oxygen.

21. What is the source of the water that results from aerobic respiration?

A. The condensation of carbon dioxide and protons.

B. The degradation of glucose into pyruvate.

C. The reduction of oxygen, the terminal electron acceptor.

D. The oxidative decarboxylation of pyruvate.

E. The reduction of pyruvate to lactic acid.

22. What biochemical pathway describes most completely the oxidation of glucose to carbon dioxide and water?

A. fermentation.

B. oxidative phosphorylation.

C. aerobic respiration.

D. Krebs cycle.

E. glycolysis.

23. What biochemical pathway describes most completely the oxidation of acetate?

A. fermentation.

B. oxidative phosphorylation.

C. aerobic respiration.

D. Krebs cycle.

E. glycolysis.

24. What biochemical pathway describes most completely the oxidative break down of glucose to pyruvate?

A. fermentation.

B. oxidative phosphorylation.

C. aerobic respiration.

D. Krebs cycle.

E. glycolysis.

25. What biochemical pathway describes most completely the oxidation of glucose to lactic acid?

A. fermentation.

B. oxidative phosphorylation.

C. aerobic respiration.

D. Krebs cycle.

E. glycolysis.

26. What biochemical pathway describes most completely the synthesis of ATP using the energy of a proton gradient?

A. fermentation.

B. oxidative phosphorylation.

C. aerobic respiration.

D. Krebs cycle.

E. glycolysis.

27. The end product of the glycolys is

A. oxygen

B. pyruvate

C. coenzyme I

D. water

E. ethanol

28. Identify the end product of aerobic respiration.

A. oxygen

B. pyruvate

C. coenzyme I

D. water

E. ethanol

29. Identify the final electron acceptor of aerobic respiration.

A. oxygen

B. pyruvate

C. coenzyme I

D. water

E. ethanol

30. Identify an end product of fermentation.

A. oxygen

B. pyruvate

C. coenzyme I

D. water

E. ethanol

31. Identify an intermediate electron carrier.

A. oxygen

B. pyruvate

C. coenzyme I

D. water

E. ethanol

32. Organisms that derive all their energy from the oxidation of inorganic compounds (e.g., rocks) are called

A. photo-organotrophs.

B. photo-lithotrophs.

C. chemo-organotrophs.

D. chemo-lithotrophs.

E. C-heterotrophs.

33. Organisms that derive all their energy from the oxidation of organic

compounds are called

A. photo-organotrophs.

B. photo-lithotrophs.

C. chemo-organotrophs.

D. chemo-lithotrophs.

E. C-heterotrophs.

34. Organisms that derive all energy from oxidation of chemicals are called

A. chemotrophs.

B. organotrophs.

C. lithotrophs.

D. phototrophs.

E. C-heterotrophs.

35. Organisms that use organic molecules as primary electron donors of their energy metabolism are called

A. chemotrophs.

B. organotrophs.

C. lithotrophs.

D. phototrophs.

E. C-heterotrophs.

36. Organisms that use inorganic molecules as primary electron donors of their energy metabolism are called

A. chemotrophs.

B. organotrophs.

C. lithotrophs.

D. phototrophs.

E. C-heterotrophs.

37. Organisms that derive all their carbon from (preformed) organic molecules are

A. respiring.

B. fermenting.

C. chemoorganotrophs.

D. C-heterotrophs.

E. C-autotrophs.

38. Organisms that derive all their carbon from inorganic carbon, chiefly carbon dioxide are

A. respiring.

B. fermenting.

C. chemoorganotrophs.

D. C-heterotrophs.

E. C-autotrophs.

39. Chemoorganotrophs that use an external, inorganic molecule as terminal electron acceptor in their energy metabolism are

A. respiring.

B. fermenting.

C. phototrophs

D. C-heterotrophs.

E. C-autotrophs.

40. Chemoorganotrophs that use an internal, organic molecule as a terminal electron acceptor in their energy metabolism are

A. respiring.

B. fermenting.

C. phototrophs

D. C-heterotrophs.

E. C-autotrophs.

41. Chemiosmosis allows exergonic redox processes to drive the endergonic reaction in which:

A. ADP is produced by dephosphorylation of ATP.

B. glucose is produced from phosphorylation of ADP.

C. G3P is produced from phosphorylation of ADP.

D. ATP is produced by phosphorylation of ADP.

E. pyruvate is converted to acetyl CoA.

42. Coenzyme Q:

A. transfers electrons.

B. oxidizes glucose.

C. is the ultimate source of energy in the citric acid cycle.

D. transfers phosphate to ATP.

E. reduces glucose.

43. The role of the oxygen molecules required for aerobic respiration is:

A. to accept the low energy electrons at the end of the electron transport chain.

B. to form ATP.

C. to produce CO2.

D. to store high energy electrons to pass to complex I of the electron transport chain.

E. to accept electrons directly from either NADH or FADH2.

44. During aerobic respiration, oxygen is:

A. formed.

B. reduced.

C. oxidized.

D. catabolized.

E. decarboxylated.

45. Which of the following steps in the Kreb’s cycle directly produces a molecule of ATP (or GTP)?

A. citrate → isocitrate

B. isocitrate → α-ketoglutarate

C. succinyl CoA → succinate

D. succinate → fumarate

E. malate → oxaloacetate

46. A drowning death would be most directly due to:

A. The unavailability of glucose to feed into glycolysis.

B. The accumulation of lactate in the muscle tissue due to anaerobic respiration.

C. The breakdown of pyruvate into ethyl alcohol.

D. The lack of oxygen to accept hydrogen.

E. There is not sufficient information to determine which answer is correct.

47. Organismal body heat is a:

A. byproduct of endergonic reactions.

B. product of glucose synthesis.

C. byproduct of exergonic reactions.

D. product of anabolism.

E. product of ATP synthesis.

48. Peter Mitchell demonstrated ATP production by aerobic bacteria by placing the bacteria in:

A. an acidic environment.

B. a basic environment.

C. an aqueous environment.

D. a buffered environment.

E. None of these is correct.

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

A. Protons are pumped out of the mitochondria by the complexes of the electron transport chain.

B. The proton gradient established during electron transport is a form of potential energy.

C. The electron transport chain can be found in the mitochondria of aerobic bacteria and other cells.

D. The movement of protons down a concentration gradient is an endergonic process.

E. ATP synthesis associated with the electron transport chain is an example of substrate level phosphorylation.

50. When hydrogen ions (protons) are pumped across the inner mitochondrial membrane, they form a proton gradient. ATP is then formed by a process known as:

A. glycolysis.

B. the citric acid cycle.

C. chemiosmosis.

D. pyruvate synthesis.

E. substrate-level phosphorylation.

51. In chemiosmosis, ATP is produced as hydrogen ions (protons) pass through:

A. the outer mitochondrial membrane.

B. ATP synthase.

C. ATP dehydrogenase.

D. ATP decarboxylase.

E. a series of electron carriers.

52. Select the processes that are matched with the incorrect amount of ATP produced by that process per glucose molecule.

A. glycolysis—2 ATP (net)

B. citric acid cycle—4 ATP

C. electron transport chain—32 ATP

D. alcohol fermentation—2 ATP

E. lactate fermentation—2 ATP

53. Select the incorrect match between the molecule and the amount of ATP produced if that particular molecule is completely oxidized in aerobic respiration:

A. FAD—2 ATP

B. NAD—2 ATP

C. glucose—36 to 38 ATP

D. pyruvic acid—34 to 36 ATP

E. All of these answer choices are correctly matched.

54. In the skeletal muscle cells of vertebrates, as many as ____________ molecules of ATP are produced from one molecule of glucose. This is less than might be expected, because electrons from NADH produced during glycolysis must be shuttled through the ____________ mitochondrial membrane at a cost.

A. 2; outer

B. 2; inner

C. 38; inner

D. 6; outer

E. 36; inner

55. One important regulation point in the aerobic respiration of mammals occurs in glycolysis at the site of the enzyme phosphofructokinase, which is:

A. inhibited by high levels of ATP.

B. inhibited by low levels of ATP.

C. inhibited by high levels of AMP.

D. activated by the presence of O2.

E. activated by the introduction of glucose.

56. Deamination of amino acids in mammals yields amino groups that are converted to ____________, which is(are) excreted, and ____________, which is(are) converted to one of the reactants of glycolysis or the citric acid cycle.

A. urea; carbon chains

B. amino acids; ATP

C. amino groups; ADP

D. carbon chains; amino acids

E. amines; ATP

57. One gram of ____________ contains more than twice the amount of energy of a gram of glucose.

A. amino acids

B. lipids

C. ATP

D. protein

E. starch

58. Which of the following molecules can be used as a substrate for cellular respiration?

A. glucose

B. lipids

C. proteins

D. fatty acids

E. All of these.

59. Saturated fatty acids store more energy than unsaturated fatty acids. Based on your knowledge of aerobic respiration, you draw this conclusion because saturated fatty acids:

A. are more highly reduced.

B. are deaminated.

C. lack phosphate.

D. contain more ester linkages.

E. contain more ATP.

60. Anaerobic respiration differs from aerobic respiration in that anaerobic respiration:

A. can utilize NO3- as the terminal electron acceptor.

B. can utilize O2 as the terminal electron acceptor.

C. produces CO2.

D. produces ATP.

E. involves an electron transport chain.

61. The production of alcohol or lactate from pyruvate during ____________ occurs as a means of regenerating ____________ from ____________.

A. aerobic respiration; NAD+; NADH

B. fermentation; NAD+; NADH

C. fermentation; NADH; NAD+

D. fermentation; ADP; ATP

E. aerobic respiration; ATP; ADP

62. During fermentation, the immediate fate of the electrons in NADH is that they:

A. are transferred to the electron transport chain.

B. are transferred to an organic molecule.

C. are transferred to O2.

D. are used to make CO2.

E. are used to form H2O.

63. If yeasts are grown under anaerobic conditions, pyruvate is converted first to ______ and then to _______.

A. citrate; oxaloacetate

B. acetyl coenzyme A; citrate

C. lactate; carbon dioxide

D. acetaldehyde; ethyl alcohol

E. acetaldehyde; lactate

64. Select the molecule that contains the most stored chemical energy:

A. ethyl alcohol.

B. water.

C. carbon dioxide.

D. lactate.

E. oxygen.

65. Select the molecule that contains the least stored chemical energy:

A. ethyl alcohol.

B. pyruvate.

C. glucose.

D. lactate.

E. oxygen.

66. The ability of some bacteria to produce lactate is exploited by humans to make:

A. cheese and ethyl alcohol.

B. insulin and antibodies.

C. yogurt and sauerkraut.

D. ethyl alcohol and carbonic acid.

E. carbon dioxide and water.

67. Which of the following statements is not correct about lactic acid fermentation?

A. It is inefficient compared to aerobic respiration.

B. It uses glucose as a substrate.

C. It produces two ATP molecules for every glucose molecule.

D. Oxygen is the final electron acceptor of this pathway.

E. Glycolysis is the only energy-yielding step of this pathway.

68. Dehydrogenase enzymes remove hydrogen atoms from fuel molecules and transfer them to acceptors such as

A. O2 and H20

B. ATP and FAD

C. NAD+ and FAD

D. CO2 and H2O

E. CoA and pyruvate

69. Which of the following is a major source of electrons for the electron transport chain?

A. H20

B. ATP

C. NADH

D. ATP synthase

E. coenzyme A

70. In the process of _________, electron transport and ATP synthesis are coupled by a proton gradient across the inner mitochondrial membrane.

A. chemiosmosis

B. deamination

C. anaerobic respiration

D. glycolysis

E. decarboxylation

71. Which of the following is a common energy flow sequence in aerobic respiration, starting with the energy stored in glucose?

A. glucose—NADH—pyruvate—ATP

B. glucose—ATP—NADH—electron transport chain

C. glucose—NADH—electron transport chain—ATP

D. glucose—oxygen—NADH—water

E. glucose—FADH2—NADH—coenzyme A

72. Which multiprotein complex in the electron transport chain is responsible for reducing molecular oxygen?

A. complex I (NADH-ubiquinone oxidoreductase)

B. complex II (succinate-ubiquinone reductase)

C. complex III (ubiquinone-cytochrome c oxidoreductase)

D. complex IV (cytochrome c oxidase)

E. complex V (ATP synthase)

73. A net profit of only 2 ATPs can be produced anaerobically from the _____________ of one molecule of glucose, compared with a maximum of 38 ATPs produced in ________________.

A. fermentation; anaerobic respiration

B. anaerobic respiration; fermentation

C. aerobic respiration; fermentation

D. dehydrogenation; decarboxylation

E. fermentation; aerobic respiration

74. When deprived of oxygen, yeast cells obtain energy by fermentation, produced carbon dioxide, ATP, and

A. acetyl CoA

B. ethyl alcohol

C. lactate

D. pyruvate

E. citrate

75. During strenuous muscle activity, the pyruvate in muscle cells may accept hydrogen from NADH to become ______________.

A. acetyl CoA

B. ethyl alcohol

C. lactate

D. pyruvate

E. citrate

76. Which of the following is the major source of electrons that flow through the mitochondrial electron transport chain?

a. H2O.

b. ATP.

c. NADH + H+

d. ATP synthase/ ATPase.

e. Coenzyme A.

77. The “aerobic” part of aerobic cellular respiration occurs during

a. Glycolysis.

b. The oxidative decarboxylation of pyruvate.

c. The citric acid cycle.

d. Electron transport.

e. Ethanol fermentation.

78. Substrate-level phosphorlation

a. Occurs through a chemiosmotic mechanism.

b. Accounts for most of the ATP formed during aerobic cellular respiration.

c. Occurs during glycolysis and citric acid cycle.

d. Occurs during the conversion of pyruvate to acetyl CoA.

e. Requires high energy electrons from NADH+H+

79. Which of the following is a correct ranking of molecules, according to their energy value in oxidative phosphorylation?

a. ATP = NADH+H+

b. NAD+ > NADH+H+

c. FAD > FADH2

d. NADH+H+ > ATP

80. A net profit of only 2 ATPs can be produced anaerobically from the ______ of onemolecule of glucose, compared with a maximum of 38 ATPs in _______.

a. Fermentation; anaerobic respiration.

b. Aerobic respiration; fermentation.

c. Aerobic respiration; anaerobic respiration.

d. Dehydrogenation; decarboxylation.

e. Fermentation; aerobic respiration.

81. When deprived of oxygen, yeast cells obtain energy by fermentation, producing carbon dioxide, ATP, and

a. Acetyl CoA.

b. Ethyl alcohol.

c. Lactate.

d. Pyruvate.

e. Citrate.

True/False

82. Substrate-level phosphorylation reactions occur in the process of chemiosmosis. _______

83. The stage of cellular repiration in which most of the ATP is produced is the TCA. ______

84. The downhill flow of protons through the ATP synthase complex powers the production of ATP. ____

85. In liver cells, each NADH+H+ produced via glycolysis results in two ATP molecules in the electron transport chain. ______

86. Phosphofructokinase is stimulated by high levels of ATP. ______

87. In the process of aerobic respiration, nitrate can function as a terminal electron acceptor in the electron transport chain. ______

88. If Saccharomyces yeast cells are incubated under anaerobic conditions, the pyrvate they produce is converted to lactate. _______

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