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MCB 229 Spring 2000 Study Guide 7 Prof. Terry
Covers Lecture for Feb. 22

This study guide is intended for you to use while you are doing the assigned text reading. Quiz questions will be made with reference to topics in this study guide. Quiz #7, based on questions from this study guide, must be completed by midnight before the class on Tuesday, Feb. 22. You will need to create your "myWebCT" account and visit the MCB 229 WebCT page in order to access this quiz.

Chapter 9 (p. 169-174; 176-179); also see Appendix Fig. AII.4 (p. A16)
  1. Pyruvate is the end product of glycolysis (or Entner-Doudoroff) pathways. If an external electron acceptor is available (respiration), then pyruvate can be further oxidized by the TCA cycle. But pyruvate must first be decarboxylated (CO2 removed) and oxidized. What is the name of the multienzyme system that carries out this reaction? What product is produced? What redox carrier is involved?
  2. The TCA cycle (a.k.a. Krebs cycle, citric acid cycle) can works as an "oxidation superburner". It allows electrons to be removed at several points. Using Fig. 9.7 and/or Fig. AII.4, identify the oxidation reactions in the TCA pathway (hint: there are 4 of them). What redox carriers are involved? For one complete cycle, which reduced redox carriers are produced and in what amounts?
  3. Do decarboxylation reactions also occur in the TCA cycle? If so, where?
  4. I don't require you to memorize the compounds or the enzymes involved in the TCA cycle, but I do suggest that you spend a couple of minutes comparing the diagram in Fig. AII.4 with the text on p. 169 (upper right column).
  5. Do strictly fermentative organisms use the TCA cycle? Logically no, since they need to use their pyruvate as an electron acceptor. But most of the enzymes of the TCA cycle are found in many non-respiring microbes, because this cycle also serves anabolic needs.
  6. The electron transport system (ETS) makes possible respiration, an alternative way to get rid of electrons produced in oxidation reactions. In fermentation, _________ served as the acceptor for electrons. In respiration, what serves as the electron acceptor? ___________.
  7. Where is the electron transport chain located in eucaryotic cells? ___________ In bacterial cells? ______________ .
  8. The components of the ETS include several protein complexes and a couple of electron carriers that move between the complexes. The identity of these carriers differs between different organisms. What are the names of principal ETS electron carriers used in mitochondria (see Fig. 9.8)? (hint: there are 7 of them).
  9. What does the chemiosmotic hypothesis predict?
  10. What is protonmotive force (PMF)? In bacteria, which side of the membrane has more protons? How do bacteria use the energy of PMF?
  11. Compare the structure of ATP synthase with other enzymes; what is unusual about it? (see Fig. 9.12) Where is this enzyme located? Which way does the head face in bacterial cells? What does this enzyme do? How does it get its energy?
  12. How do chemicals such as cyanide or azide affect respiration? How do uncouplers such as dinitrophenol or valinomycin affect respiration?
  13. What is the maximum theoretical ATP yield from the aerobic respiration of glucose in mitochondria? Do bacteria obtain the same yields? How does this compare to the ATP yield from glycolysis?
  14. Although we usually equate "respiration" with the consumption of oxygen, some bacteria use other electron acceptors with a modified ETS; this is called anaerobic respiration. What electron acceptors are used in anaerobic respiration? What are the reduced products formed in each case?
  15. So far, we have looked only at glucose as an energy source. Microbes can degrade other materials, including a variety of carbohydrates, lipids, and proteins. In each case, cells need specific enzymes to activate appropriate catabolic pathways. The remaining few questions direct your attention to a few of these catabolic reactions, as described and diagrammed on pp. 178-179. Fear not, the end is near!
  16. Suppose the substrate growth is not glucose but some other monosaccharide such as galactose or fructose. What modifications must the cell make in its catabolic machinery?
  17. Suppose the substrate for growth is a disaccharide such as lactose or sucrose. What modifications must the cell make in its catabolic machinery?
  18. Suppose the substrate for growth is a polysaccharide such as starch. What modifications must the cell make in its catabolic machinery? Are most bacteria equally able to make adaptations for growth on cellulose? Agar?
  19. When cells attempt to use lipids as their growth substrate, they must shift gears dramatically. Fatty acids are often the most abundant energy source in lipids. What pathway handles fatty acid oxidation? (hint: see Fig. 9.17) What is the product that enters into central metabolism via the TCA cycle? (hint: it has 2 C-atoms).
  20. If proteins are used as growth substrates, how are they broken down? What is the first step in catabolism of amino acids? What major catabolic pathways subsequently oxidizes these products?
  21. Whew!!! You're done! I'll try to be especially kind in writing the quiz questions on this stuff – I know there's a lot of material here.