Question 1

The skunk cabbage (Symphocarpus foetidus) can maintain a temperature of 10-25 °C higher than the temperature of the surrounding air. Suggest a mechanism for this.

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Question 2

The compound 2,4-dinitrophenol (DNP), an uncoupler, was briefly used as a weight-loss drug. Some of its effects in people who took the drug included weight loss and higher than normal body temperature. Some people even died. Explain the first two effects of the compound in biochemical terms.

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Question 3

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

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Question 4

Consider a liver cell carrying out the oxidation of glucose under aerobic conditions. Suppose that we added a very potent and specific inhibitor of the mitochondrial ATP synthase, completely inhibiting this enzyme. Indicate whether each of the following statements about the effect of this inhibitor is true or false; if false, explain in a sentence or two why it is false.
____ (a) ATP production in the cell will quickly drop to zero.
____ (b) The rate of glucose consumption by this cell will decrease sharply.
____ (c) The rate of oxygen consumption will increase.
____ (d) The citric acid cycle will speed up to compensate.
____ (e) The cell will switch to fatty acid oxidation as an alternative to glucose oxidation, and the inhibitor will therefore have no effect on ATP production.

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Question 5

Mutations in mitochondrial genes frequently produce diseases that affect the brain and skeletal muscle (mitochondrial encephalomyopathies). Why are these two tissues particularly sensitive to mitochondrial mutations?

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Question 6

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

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Question 7

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each:
(1) NADH
(2) Inorganic phosphate
(3) ADP

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Question 8

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.

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Question 9

In his studies of alcoholic fermentation by yeast, Louis Pasteur noted that the sudden addition of oxygen (O₂) to a previously anaerobic culture of fermenting grape juice resulted in a dramatic decrease in the rate of glucose consumption. This "Pasteur effect" can be counteracted by the addition of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. (a) Why would the yeast cells consume less glucose in the presence of oxygen? Can you estimate how much less glucose they would use? (b) Why would DNP counteract or prevent the Pasteur effect?

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Question 10

When the $\Delta$G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

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Question 11

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

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Question 12

Although molecular oxygen (O₂) does not participate directly in any of the reactions of the citric acid cycle, the cycle operates only when O₂ is present. Explain this observation.

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Question 13

Give an example of (a) an uncoupler of oxidative phosphorylation, and (b) an inhibitor of respiration. (c) Describe the difference in the effects of such uncouplers and inhibitors on mitochondrial function.

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Question 14

Describe the role of cytochrome c in apoptosis.

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Question 15

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

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Question 16

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

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Quiz 19: Oxidative Phosphorylation and Photophosphorylation

The skunk cabbage (Symphocarpus foetidus) can maintain a temperature of 10-25 °C higher than the temperature of the surrounding air. Suggest a mechanism for this.

The compound 2,4-dinitrophenol (DNP), an uncoupler, was briefly used as a weight-loss drug. Some of its effects in people who took the drug included weight loss and higher than normal body temperature. Some people even died. Explain the first two effects of the compound in biochemical terms.

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

Mutations in mitochondrial genes frequently produce diseases that affect the brain and skeletal muscle (mitochondrial encephalomyopathies). Why are these two tissues particularly sensitive to mitochondrial mutations?

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each: (1) NADH (2) Inorganic phosphate (3) ADP

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.

When the $\Delta$ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

Although molecular oxygen (O₂) does not participate directly in any of the reactions of the citric acid cycle, the cycle operates only when O₂ is present. Explain this observation.

Give an example of (a) an uncoupler of oxidative phosphorylation, and (b) an inhibitor of respiration. (c) Describe the difference in the effects of such uncouplers and inhibitors on mitochondrial function.

Describe the role of cytochrome c in apoptosis.

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Quiz 19: Oxidative Phosphorylation and Photophosphorylation

The skunk cabbage (Symphocarpus foetidus) can maintain a temperature of 10-25 °C higher than the temperature of the surrounding air. Suggest a mechanism for this.

The compound 2,4-dinitrophenol (DNP), an uncoupler, was briefly used as a weight-loss drug. Some of its effects in people who took the drug included weight loss and higher than normal body temperature. Some people even died. Explain the first two effects of the compound in biochemical terms.

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

Mutations in mitochondrial genes frequently produce diseases that affect the brain and skeletal muscle (mitochondrial encephalomyopathies). Why are these two tissues particularly sensitive to mitochondrial mutations?

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each: (1) NADH (2) Inorganic phosphate (3) ADP

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and Pi.

When the Δ\DeltaΔ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

Although molecular oxygen (O2) does not participate directly in any of the reactions of the citric acid cycle, the cycle operates only when O2 is present. Explain this observation.

Give an example of (a) an uncoupler of oxidative phosphorylation, and (b) an inhibitor of respiration. (c) Describe the difference in the effects of such uncouplers and inhibitors on mitochondrial function.

Describe the role of cytochrome c in apoptosis.

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

When the F1 portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.

When the $\Delta$ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Although molecular oxygen (O₂) does not participate directly in any of the reactions of the citric acid cycle, the cycle operates only when O₂ is present. Explain this observation.

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?