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Exam 19: Oxidative Phosphorylation and Photophosphorylation

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Question 31

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Describe what happens when a photon is absorbed by photosystem II;end the description of electron flow at plastoquinone.

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Absorption of a photon by PSII excites P...

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Question 32

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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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(a)Uncouplers include DNP,valinomycin,an...

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Question 33

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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?

In photophosphorylation,absorption of light energy in chloroplast "light reactions" leads to:

Compound X is an inhibitor of mitochondrial ATP synthesis.It was observed that when compound X was added to cells,the NAD⁺/NADH ratio decreased.Would you expect X to be an uncoupling agent or an inhibitor of respiratory electron transfer? Explain.

When the $\Delta$ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme,it is found to be close to zero.This is thought to be due to:

In normal mitochondria,the rate of NADH consumption (oxidation) will:

The processes of oxidative phosphorylation coupled with electron transfer (in mitochondria)and photophosphorylation (in chloroplasts)resemble each other in certain respects.Describe five ways in which the two processes are similar,and describe three significant differences between the two processes.

Reduced QH₂ is not formed by which of the following?

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

Give five general classes of electron carriers that function in both mitochondrial electron transfer to O₂ and photosynthetic electron transfer.

Describe the effect(s)that a mitochondrial uncoupler such as 2,4-dinitrophenol (DNP)would have on photophosphorylation.

Almost all of the oxygen (O₂) one consumes in breathing is converted to:

Antimycin A blocks electron transfer between cytochromes b and c₁.If intact mitochondria were incubated with antimycin A,excess NADH,and an adequate supply of O₂,which of the following would be found in the oxidized state?

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.

Cyanide ion (CN^-)blocks electron transfer in mitochondria at the level of cytochrome a + a₃.2,4-Dinitrophenol (DNP)is an uncoupler of mitochondrial oxidative phosphorylation.Draw graphs (ATP synthesized vs.time and O₂ consumed vs.time)with labeled curves to show the effects of adding each of these compounds separately to a suspension of mitochondria supplied with O₂,succinate,ADP,and P_i.Use an arrow to indicate the time of drug addition.

Describe the role of cytochrome c in apoptosis.

Which one of the following best describes the role of mitochondria in apoptosis?

As you read and answer this question,you are (presumably)consuming oxygen.What single reaction accounts for most of your oxygen consumption?

Cyanide,oligomycin,and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation.Which of the following statements correctly describes the mode of action of the three inhibitors?