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Unformatted text preview: Homework #4 Ch 17 and 19 Name___________________ Answer all 20 Questions: 15 points for trying all, 3‐questions will be spot checked for correct answers. 30 points total. 1. A new compound isolated from mitochondria is claimed to represent a previously unrecognized carrier in the electron transfer chain. It is given the name coenzyme Z. Which line of evidence do you feel is the least conclusive in assigning this compound a position in the electron transfer chain? A) Alternate oxidation and reduction of the mitochondrion‐bound coenzyme Z can be readily demonstrated. B) Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen consumption. C) The rate of oxidation and reduction of mitochondrion‐bound coenzyme is of the same order of magnitude as the overall rate of electron transfer in mitochondria as measured by oxygen consumption. D) The reduction potential of Z is between that of two compounds known to participate in the electron transport chain E) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and specifically by the mitochondria. 2. Fatty acids are activated to acyl‐CoAs and the acyl group is further transferred to carnitine because: A) acyl‐carnitines readily cross the mitochondrial inner membrane, but acyl‐CoAs do not. B) acyl‐CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will not. C) carnitine is required to oxidize NAD+ to NADH. D) fatty acids cannot be oxidized by FAD unless they are in the acyl‐carnitine form. E) None of the above is true. 3. If the 16‐carbon saturated fatty acid palmitate is oxidized completely to carbon dioxide and water (via the β‐oxidation pathway and the citric acid cycle), and all of the energy‐
conserving products are used to drive ATP synthesis in the mitochondrion, the net yield of ATP per molecule of palmitate is: A) 3. B) 10. C) 25. D) 108. E) 1,000. 4. Complete oxidation of 1 mole of which fatty acid would yield the most ATP? A)
E) 16‐carbon saturated fatty acid 18‐carbon mono‐unsaturated fatty acid 16‐carbon mono‐unsaturated fatty acid 16‐carbon poly‐unsaturated fatty acid 14‐carbon saturated fatty acid 5. The balanced equation for the degradation of CH3(CH2)10COOH via the β‐oxidation pathway is: A) CH3(CH2)10COOH + 5FAD + 5NAD+ + 6CoA—SH + 5H2O + ATP →
6 Acetyl‐CoA + 5FADH2 + 5NADH + 5H+ + AMP + PPi B) CH3(CH2)10COOH + 5FAD + 5NAD+ + 6CoA—SH + 5H2O →
6 Acetyl‐CoA + 5FADH2 + 5NADH + 5H+ C) CH3(CH2)10COOH + 6FAD + 6NAD+ + 6CoA—SH + 6H2O + ATP →
6 Acetyl‐CoA + 6FADH2 + 6NADH + 6H+ + AMP + PPi D) CH3(CH2)10COOH + 6FAD + 6NAD+ + 6CoA—SH + 6H2O →
6 Acetyl‐CoA + 6FADH2 + 6NADH + 6H+ 6. Which enzyme is the major regulatory control point for β‐oxidation? A) pyruvate carboxylase B) carnitine acyl transferase I
C) acetyl CoA dehydrogenase
D) enoyl CoA isomerase
E) methylmalonyl CoA mutase 7. The major site of formation of acetoacetate from fatty acids is the: A) adipose tissue. B) intestinal mucosa. C) kidney. D) liver. E) muscle. 8. 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? A) Coenzyme Q B) Cytochrome a3 C) Cytochrome b D) Cytochrome e E) Cytochrome f 9. 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? A) Cyanide and 2,4‐dinitrophenol inhibit the respiratory chain, and oligomycin inhibits the synthesis of ATP.
B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4‐dinitrophenol inhibit the synthesis of ATP. C) Cyanide, oligomycin, and 2,4‐dinitrophenol compete with O2 for cytochrome oxidase (Complex IV). D) Oligomycin and cyanide inhibit synthesis of ATP; 2,4‐dinitrophenol inhibits the respiratory chain. E) Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4‐dinitrophenol prevent the synthesis of ATP. 10. Which of the following statements about the chemiosmotic theory is correct? A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. B) It predicts that oxidative phosphorylation can occur even in the absence of an intact inner mitochondrial membrance. C) The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes. D) The membrane ATP synthase has no significant role in the chemiosmotic theory. E) All of the above are correct. 11. Uncoupling of mitochondrial oxidative phosphorylation: A) allows continued mitochondrial ATP formation, but halts O2 consumption. B) halts all mitochondrial metabolism. C) halts mitochondrial ATP formation, but allows continued O2 consumption. D) slows down the citric acid cycle. E) slows the conversion of glucose to pyruvate by glycolysis. 12. 2,4‐Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4‐Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4‐dinitrophenol will: A)
E) allow electron transfer in the presence of oligomycin. allow oxidative phosphorylation in the presence of oligomycin. block electron transfer in the presence of oligomycin. diminish O2 consumption in the presence of oligomycin do none of the above. 13. When the ΔG'° 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: A) a very low energy of activation. B) enzyme‐induced oxygen exchange. C) stabilization of ADP relative to ATP by enzyme binding. D) stabilization of ATP relative to ADP by enzyme binding. E) none of the above. 14. The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O ratio of less than 2. The initial oxidation step is very likely directly coupled to the: A) oxidation of a flavoprotein. B) oxidation of a pyridine nucleotide. C) reduction of a flavoprotein. D) reduction of a pyridine nucleotide. E) reduction of cytochrome a3. 15. In photophosphorylation, absorption of light energy in chloroplast “light reactions” leads to: A) absorption of CO2 and release of O2. B) absorption of O2 and release of CO2. C) hydrolysis of ATP and reduction of NADP+. D) synthesis of ATP and oxidation of NADPH. E) use of iron‐sulfur proteins. 16. Oxidative phosphorylation and photophosphorylation share all of the following except: A) chlorophyll. B) involvement of cytochromes. C) participation of quinones. D) proton pumping across a membrane to create electrochemical potential. E) use of iron‐sulfur proteins. 17. In the photolytic cleavage of water by the oxygen‐evolving complex [2H2O → 4 H+ + 4e– + O2], how many photons of light at a wavelength of 680 nm are required? A) 1 B) 2 C) 4 D) 6 E) 8 18. Which one of the following is true about reaction centers? A) Cyanobacteria and plants have two reaction centers arranged in tandem. B) Cyanobacteria contain a single reaction center of the Fe‐S type. C) Green sulfur bacteria have two reaction centers arranged in tandem. D) Plant photosystems have a single reaction center of the pheophytin‐quinone type. E) Purple bacteria contain a single reaction center of the Fe‐S type. 19. The experimental determination of the effectiveness of light of different colors in promoting photosynthesis is called the: A) absorption spectrum. B) action spectrum. C) difference spectrum. D) reflectance spectrum. E) refraction spectrum. 20. The light reactions in photosynthetic higher plants: A) do not require chlorophyll. B) produce ATP and consume NADH. C) require the action of a single reaction center. D) result in the splitting of H2O, yielding O2. E) serve to produce light so that plants can see underground. ...
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- Fall '10