Chapter 18 - Electron Transport and Oxidative Phosphorylation Practice Quiz PDF

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This is a practice quiz for chapter 18 of biochem II. This is similar to the in class quiz. It can also serve as a study guide for the test. It also helps with the assignments. Contains questions and answers....

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1/5 Biochemistry II Chapter 18: Electron Transport and Oxidative Phosphorylation Textbook: Fundamentals of Biochemistry: Life at the Molecular Level, 5th Edition. Donald Voet; Judith G. Voet Practice Quiz 1. Match each of the following: 1. Porins that permit the free diffusion of molecules up to 10 kD are found here. 2. Respiratory chain proteins are found here. 3. Equivalent to the cytosol in its concentrations of metabolites and ions 4. The mitochondrial genetic machinery is found here. 5. Most of the ATP generated through oxidative phosphorylation is used here. Matrix

4

Inner membrane

2

Intermembrane space

3

Cytosol

5

Outer membrane

1

2. The number of cristae present in a mitochondrion reflects the respiratory activity of the cell. 3. The ADP-ATP translocator is an example of an electrogenic antiport driven by the membrane potential difference (∆Ψ).

2/5 4. Match each of the following: 1. Accepts electrons from NADH and contains a molecule of flavin mononucleotide (FMN) 2. Results in the translocation of H+ from the matrix to the intermembrane space 3. Passes electrons from reduced CoQ to cytochrome c 4. Passes electrons from succinate to CoQ 5. A peripheral membrane protein that shuttles electrons between Complexes III and IV Q cycle

2

Complex I

1

Complex III

3

Complex II

4

Cytochrome c

5

5. The respiratory complexes of the electron transport chain include several protein components that are associated with a variety of redox-active prosthetic groups with successively increasing reduction potentials. 6. Protons are translocated from the matrix to the intermembrane space as electrons are transferred between the redox centers of Complex I. 7. Electrons from FADH2 produced by the glycerophosphate shuttle pass to CoQ. 8. True or false. In bacteriorhodopsin, light absorption induces conformational changes in the protein that result in proton pumping. True.

3/5 9. True or false. The free energy for electron transfer from succinate to CoQ is sufficient to drive ATP synthesis. False. NOTE: It is not sufficient to drive ATP synthesis but serves to inject electrons into the electron transport chain. 10. True or false. Succinate added to amytal-blocked mitochondria restores O2consumption. True. NOTE: Addition of a substance "downstream" of a block restores O2 consumption. 11. True or false. Proton pumping in Complex I and Complex III occurs by the same mechanism. False. NOTE: They occur by quite different mechanisms. 12. Match each of the following: 1. The potential of the electrochemical proton gradient across the inner mitochondrial membrane is harnessed to synthesize ATP. 2. Three different conformational states in the ATP synthase, with respect to the binding of nucleotide substrates 3. Multisubunit transmembrane protein composed of two functional units. F0 and F1. 4. Proton transporting ionophore. Binding change mechanism

2

Chemiosmotic theory

1

Proton-pumping ATP synthase

3

DNP

4

13. A water-soluble portion of the proton-pumping ATP synthase (F1), when dissociated from the membrane portion, hydrolyzes ATP but cannot synthesize it. 14. The relationship between the amount of ATP synthesized to the amount of oxygen reduced is called the P/O ratio.

4/5 15. Tight coupling of electron transport to oxidative phosphorylation means that virtually the only way for protons to re-enter the mitochondrial matrix is through the F0 portion of ATP synthase. 16. True or false. The free energy of electron transport is conserved by pumping protons from the mitochondrial inner membrane space to the matrix. False. NOTE: The free energy is conserved by pumping protons from the mitochondrial matrix to the intermembrane space. 17. True or false. The free energy change of transporting a proton out of the mitochondrion is an exergonic process and strictly chemical in nature. False. NOTE: The free energy change of transporting a proton out of the mitochondrion is an endergonic process and is chemiosmotic in nature. 18. At rest the ATP mass action ratio is high and the rate of oxidative phosphorylation is minimal. 19. Citrate acts as an inhibitor of PFK or phosphofructokinase when the demand for ATP decreases. 20. Congenital defects in mitochondrial DNA cause a variety of symptoms that mimic old age. 21. Antioxidants destroy oxidative free radicals. 22. True or false. ATP activates the formation of succinyl-CoA. False. NOTE: ATP inhibits the formation of succinyl-CoA. 23. True or false. ADP activates the formation of pyruvate. True.

5/5 24. True or false. Aerobic metabolism is only slightly more efficient than anaerobic glycolysis. False. NOTE: Aerobic metabolism is about sixteen times more efficient than anaerobic metabolism....