Mcb300 Exam 2

MCB300 Exam 2 1. Which of the following statements is false? a. ATP synthase is found in all living organisms b. ATP synthase is a redox-driven proton pump c. ATP synthase can use proton motive force (PMF) to drive ATP synthesis d. ATP synthase can hydrolyze ATP to generate proton motive force (PMF) e. The Boyer model describes how rotary motion is used to synthesize ATP in ATP synthase 2. Which of the following is not associated with photosynthesis? a. Use of bacteriorhodopsin as a light-driven proton pump b. Light-driven oxidation of hydrogen sulfide in purple bacteria c. Oxygen production by Prochlorococcus d. Photoautotrophy e. All of the above are associated with photosynthesis 3. Correctly complete the following sentence: Cyclic photophosphorylation…. a. Is catalyzed by photosystem II in oxygenic phototrophs b. Is required to generate electrons for CO2 reduction in green sulfur bacteria c. Does not involve redox reactions d. Is a major source of ATP synthesis in obligately aerobic anoxygenic phototrophs e. Both “b” and “d” correctly complete the sentence 4. Correctly complete the following sentence: Syntrophic bacteria…. a. are required for conversion of biomass to methane and CO2 in methanogenic ecosystems. b. use protons as terminal electron acceptors. c. cannot grow to high density in the absence of methanogens. d. are involved in the sulfate-dependent anaerobic oxidation of methane. e. All of the above correctly complete the sentence 5. Which of the following mechanisms are not used by chemolithotrophs to bring electron donors and acceptors into close proximity? a. Symbiotic associations with eukaryotes. b. Storage of electron acceptors in large vacuoles. c. Movement between zones with high electron donor concentrations and zones with high electron acceptor concentrations. d. Cyclic photophosphorylation e. Both “a” and “d” are true 6. Correctly complete the following sentence: Metal respiration…. a. is often coupled to oxidation of glucose. b. sometimes uses tiny protein “nanowires” to transfer electrons to minerals. c. occurs only under acidic pH because Fe+3 is insoluble at neutral pH.

d. can be used to generate electricity in microbial fuel cells. e. Both “b” and “d” correctly complete the sentence 7. Which of following discoveries did not occur within the last thirty years? a. Proteorhodopsin-containing bacteria b. The existence of Prochlorococcus, the most abundant photosynthetic organism on earth c. The major role of obligately aerobic anoxygenic phototrophs in marine ecosystems d. The ABE fermentation e. Ammonia oxidizing archaea 8. Which of the following statements is false: a. Cyanobacteria are the only microbes to perform oxygenic photosynthesis. b. Cyanobacteria are responsible for approximately half of global photosynthesis c. Cyanobacteria are among the most abundant organisms on the planet. d. Cyanobacteria are the ancestors of chloroplasts in plants. e. All of the statements are true. 9. Based on the thermodynamics of the reaction, which chemolithotroph would be expected to have the highest growth yield using oxygen as the terminal electron acceptor? a. A nitrifying bacterium (Eo = +0.43 V for NO3-/NO2-) b. A nitrosifying bacterium (Eo = +0.34 V for NO2-/NH3) c. An iron oxidizing acidophile (Eo = +0.77 V for Fe+3/Fe+2) d. An iron oxidizing neutrophile (Eo = +0.2 V for Fe(OH)3 + HCO3-/FeCO3) e. A phosphite oxidizing bacterium (Eo = -0.69 V for HPO4-2/HPO3-2) 10. Which of the following is not energized by ion motive force in microbes? a. Rotation of the flagellum b. ATP synthesis c. Uptake of nutrients d. Substrate level phosphorylation e. Maintenance of cytoplasmic salt concentrations 11. Which chemolithotrophs would be expected to use reverse electron transport for CO2 fixation using the Calvin cycle (hint: requires NADPH; Eo = -0.32 V for NADP/NADPH)? a. A nitrifying bacterium (Eo = +0.43 V for NO3-/NO2-) b. A nitrosifying bacterium (Eo = +0.34 V for NO2-/NH3) c. An hydrogen oxizing acidophile (Eo = -0.42 V for 2H+/H2) d. A phosphite oxidizing bacterium (Eo = -0.69 V for HPO4-2/HPO3-2) e. Both “a” and “b” 12. Which of the following is assimilation?

a. b. c. d. e.

Use of nitrate as a nitrogen source Use of sulfate during anaerobic respiration Oxidation of low-grade ore during microbial leaching Production of ammonia during catabolism of amino acids Methanogenesis

13. ATP synthase acts a rotary engine for ATP synthesis. How many ATP are produced in each 360-degree rotation cycle? a. one b. two c. three d. four e. it depends on the organism 14. Which of the following statements is false? a. Chemolithautotrophs require organic substrates for growth b. Chemolithotrophs often employ reverse electron transport for CO2 fixation c. Chemolithotrophs that grow on high concentrations of hydrogen do not employ reverse electron transport during growth d. Chemolithoheterotrophs require organic substrates for growth e. There are no known chemolithotrophs that grow by oxidizing ammonia (NH3) to nitrate (NO3-) 15. If the electron transport chain uses a proton-pumping NADH dehydrogenase, a cytochrome bc1 complex and a proton-pumping cytochrome oxidase, how many protons are translocated across the membrane when one NADH is oxidized? a. eight b. ten c. four d. three e. it depends on the organism 16. Syntrophic bacteria…. a. grow very well in pure culture. b. are rarely infected by viruses. c. usually produce hydrogen during growth. d. are always found in association methanogenic archaea in natural environments. e. are only found in hydrothermal vent ecosystems. 17. Which of the following does not involve dissimilation a. Anaerobic respiration. b. Denitrification c. Synthesis of methionine from sulfate d. Reduction of iron minerals using nanowires e. All of the above involve dissimilation.

18. Which of the following is false for methanogenic archaea? a. Some species can use glucose as a growth substrate. b. Some species can grow without syntrophic bacteria. c. They are important for carbon-cycling in nitrate-rich environments. d. Both “a” and “c” are false e. Both “a” and “b” are false 19. Which of the following is true regarding chemolithotrophs a. Some chemolithotrophs use anaerobic respiration to generate ATP b. The growth substrates used by chemolithotrophs usually act as both the electron donor and the electron acceptor c. Chemolithotrophic organisms are usually obligate anaerobes d. Sulfate is a common substrate for Chemolithotrophs e. Chemolithotrophs were not discovered until the mid-1980s 20. Which answer is incorrect: CO2 fixation during oxygenic photosynthesis does not…. a. require two distinct photosystems. b. need hydrogen sulfide as an electron donor. c. require reverse electron transport. d. occur in green non-sulfur bacteria. e. utilize proteorhodopsin to generate the required ATP. 21. Which of the following is false regarding the Q cycle. a. It translocates 4H+/2 electrons b. It requires the cyt bc1 complex c. It is found only in oxygen respiring organisms d. Transfers electrons from ubiquinol to cyt c e. All of the above are true 22. Which of the following is not used as a terminal electron acceptor (TEA) for anaerobic respiration? a. Sulfate. b. Nitrogen gas c. Ferric iron d. Nitrate e. All of the above are used as TEA 23. Which of the following is false regarding the Q loop? a. It translocates 4H+/2 electrons b. It requires the cyt bc1 complex c. It is found only in oxygen respiring organisms d. Transfers electrons from ubiquinol to cyt c e. All of the above are false

24. Which is false? a. Anoxygenic photosynthesis evolved very early in Earth’s history. b. Anoxygenic photosynthesis requires an electron donor. c. Anoxygenic photosynthesis requires cyclic photophosphorylation. d. Anoxygenic photosynthesis always requires reverse electron transport. e. Anoxygenic photosynthesis occurs in some cyanobacteria. 25. Which of the following statements is true? a. Most of the methane produced on earth is derived from acetate b. Methanobacillus omelianskii is a methane producing bacterium that uses ethanol as a growth substrate c. Methanogenic microrganisms use substrate level phosphorylation to produce most of their ATP d. Both “a” and “b” are true. e. Both “b” and “c” are true. 26. Which of the following is not a known mechanism of energy conservation in microbes? a. Hydrogen cycling. b. Proton-pumping redox enzymes c. Transfer of electrons from a high potential donor to a low potential acceptor d. Quinone cycle e. Quinone loop 27. What fraction of biomass on earth is comprised of microbial viruses? a. 50% b. 5% c. 0.5% d. 0.05% e. 99.999% 28. What fraction of individual organisms on earth is comprised of microbial viruses? a. < 1% b. ~ 10% c. ~ 50% d. >90% e. > 99.999% 29. Which of the following statements regarding fermentation are false. a. Homolactate fermenters have a higher growth yields than heterolactate fermentors b. Homolactate fermenters can adjust their growth yield depending on the availability of substrates c. Ethanol fermentation is found only in yeasts

d. Some lactic acid fermentors produce significant amounts of ethanol e. Fermenting microorganisms often grow as fast as aerobic respiring organisms even though they have dramatically lower growth yields 30. Which of the following statements regarding fermentation are true? a. Fermenting organisms rely on electron transport for ATP generation b. Fermenting organisms do not generate a proton motive force c. Less than a dozen different substrate level phosphorylation reactions have been observed in all known fermenting organisms d. The ABE fermentation is an aerobic process e. All of the above are false 31. Which statement(s) is correct? a. Oxygen is highly soluble in water b. Aerobic microorganisms maintain anaerobic environments. c. Anaerobic environments comprise a small fraction of the biosphere. d. Both “a” and “b” are correct. e. Both “a” and “c” are correct. 32. Which of the following statements regarding the enzyme cofactors used in methanogenesis is false? a. They can be used as carriers of C-1 units b. They can be used as electron carriers c. They are similar to ones commonly used in bacteria d. They can be have a blue-green fluorescence e. They can act the terminal electron acceptor in the electron transport chain 33. (Short answer: 3-4 sentences at a maximum) “Microbial viruses have a huge impact on the biosphere.” Provide two examples that justify this idea and briefly explain why each supports the statement. There are many correct answers for this question. Here are some: Phage lyse 20-40% of microbial cells every day: They act as a check on microbial populations in a predator/prey relationship. Phage lyse 20-40% of microbial cells every day: the organic products from cells lysed by phage stay in the microbial population and does not enter macrobial food chains. Phage lyse 20-40% of microbial cells every day: the organic products from cells lysed by phage stays in the microbial population and is rapidly oxidized to CO2. This prevents sequestration of carbon from the atmosphere in the deep ocean. There are 1023 phage infections per second: phage are major mediators of horizontal gene transfer and this plays a powerful role in microbial evolution.