Cellular Respiration Campbell et al. Biology. 8th ed., Chapter 9 Study hint: While working through this study guide, make a list of key terms in the right margin. Usually, these terms are boldfaced in the study guides or they appear in the referenced figures. Consult one of the glossaries if you are not sure of definitions. 0. Application 1. Case study: What's wrong with Kristine? Burning legs; Low energy; High blood acidity; Fainting; Reversible blindness 2. What happens to energy stores in starvation? 3. How does arsenate poisoning work? 4. Why do untrained muscles hurt after a vigorous workout? I. Energy transfer: Redox, phosphorylation, and energy carriers 5. Autotrophs, e.g., ______________, acquire energy from _________ in a process called_______________. They convert this energy to energy stored in ___________ ___________. When needed, they _____________ these to __________ and __________. In this process, _____________________________________________. 6. Heterotrophs, e.g., ___________, acquire energy from ________________. In their digestive tract they break down ___________________ to _____________. The latter are then imported into cells and oxidized to CO2 and water. In this process, ADP is ________________ to ATP (Fig. 9.2). 7. Which monomers (chapter 5) can be broken down to yield energy? 8. Review the structure of ATP (Fig. 8.8). 9. Review: Why is ATP such a good cellular energy currency? Two reaction types are commonly used by cells to transfer energy: phosphorylation and redox reactions. 10. Distinguish between substrate level phosphorylation (Fig. 9.7 and 9.14) and oxidative phosphorylation. Note: In biochemistry the phosphate group is commonly represented by a P with a circle around it. 11. Explain redox reactions (page 163 and Fig. 9.3). Mnemonic: OIL RIG: Oxidation is loss, reduction is gain. 12. Which member of a redox pair has more energy? 13. What is the overall formula of cellular respiration (page 164)? 14. In this formula, what is the reducing/oxidizing agent? 15. What Is reduced/oxidized? 16. Oxidation of glucose is a multistep process. What are the advantages of breaking this process down in many steps? 17. Which role does NAD + play (Fig. 9.4)? Why you should have a diet rich in vitamins: NAD + is a coenzyme that humans derive from niacin, a vitamin B Other energy carriers frequently used in metabolism: NADP+ FAD+ derived from riboflavin, a vitamin B II. The steps of aerobic respiration 18. Energy harvest occurs in 3 steps in aerobes (Fig. 9.6). Name those steps. In the video that you will see in lab, 4 steps are mentioned, the forth step is “pyruvate oxdation”, after glycolysis. A. Glycolysis (splitting of sugar) (Fig. 9.9) is a 10 step process (metabolic pathway). Each step is catalyzed by a different enzyme. When studying these ten reactions in detail, keep in mind what glycolysis is supposed to achieve: split glucose into two 3-carbon molecules of pyruvate (the "do it yourself glycolysis" exercise takes pyruvate a step further to lactate). 19. What it the significance of phosphorylation in step 1? (Hint: even though the oxidation of glucose is spontaneous, it does not happen very fast without help) 20. Why is it important that step 1 is practically irreversible? 21. Step two is easily reversible - why does that not matter at this point? 22. Phosphofructokinase, which catalyzes step 3, is a major regulatory allosteric enzyme - how does it work, what is its significance, suggest effectors and inhibitors (Fig. 9.21). 23. In step 5 we end up with two interchangeable 3-carbon sugars, step 6 only uses glyceraldehyde phosphate. How does this happen and what is the advantage? 24. How does arsenate poisoning work (see step 6 in fig. 9.9) 25. Balance input and output of glycolysis . For this and the following input/output tables, please know where reactant come from and where products go. Think of the transfer of electrons (oxidation/dehydrogenation and reduction/hydrogenation) and phosphate groups (Fig. 9.8). Input Output Sideline: Fermentation in anaerobes (pp. 177-179) Anaerobes use glycolysis to get 2 moles of ATP per mole of glucose. Hydrolysis of ATP to ADP in cells has a delta G of -10 to -14 kcal/mol A glucose molecule contains -686 kcal/mol. So the efficiency is low: around 2%. 26. What is the consequence of the low energy efficiency for anaerobes (or: why can’t anaerobic bacteria run a marathon?) 27. Besides the low efficiency, which two additional problems occur? 28. Distinguish between alcoholic and lactic acid fermentation (fig. 9.18) Alcoholic fermentation Lactic acid fermentation Starting products End product Cells that do it 29. What happens to the lactate generated by our muscle cells under anaerobic conditions? 30. Why are cells of the nervous system the first cells to die from a lack of oxygen (three reasons)? Hint: Remember this answer for the Kristin question. The aerobe solution A. Glycolysis (cytosol) B. Pyruvate oxidation in mitochondria (Fig. 9.10) 31. Which agent is oxidized? Which agent is reduced? From where to where is energy transferred? 32. Describe the three coupled reactions within the mitochondria (p. 170) 33. What happens to Acetyl CoA if there is enough ATP (p. 180: Biosynthesis). If the cell needs more ATP right then and there, Acetyl-CoA goes into C. Citric acid (Krebs) cycle (Fig. 9.11-9.12)) The citric acid cycle consists of a series of enzyme-catalyzed steps, similar to glycolysis - but this is cyclic. It happens in the mitochondria, not in the cytosol. 34. What is oxidized? What is reduced? 35. How many turns of the cycle does it take to complete the oxidation of one glucose molecule? 36. How can the Citric Acid cycle intermediate citrate be used to regulate the rate of ATP synthesis? (Fig. 9.21). 37. Tally input and output of the citric acid cycle. Input Recycled Output 38. After the Calvin cycle, glucose has been completely oxidized. Where is its energy now? Energy carrier (quantify) Produced in which process? Glycolysis Citric Acid cycle (don’t forget pyruvate oxidation) You see that we have not generated much ATP (our ultimate goal) yet. In the next step, oxidative phosphorylation, we will transfer the energy stored in our intermediate energy carriers, NADH and FADH2 to ATP. D. Oxidative phosphorylation 39. Last step happens parallel to the others. Be able to explain the process, including respiratory (electron transport) chain (Fig. 9.16) proton-motive-force (p. 176) chemiosmosis by ATP synthase (fig. 9.14) 40. The process of chemiosmosis should remind you of a process encountered in the membrane chapter. Which is it and what are similarities and differences? 41. Again, let's tally the input and output. INPUT OUTPUT Summary of cellular respiration 42. What is oxidized? Is that an exergonic or endergonic reaction? 43. What is reduced? 44. What is that energy used for? 45. Where does the energy for the endergonic synthesis of ATP come from? 46. In which order are the energy carriers of the ETC arranged? 47. How many ATP can be synthesized from the conversion o f NADH and FADH depends on many factors. E.g., the electrochemical gradient across the inner mitochondrial membrane might be used for other work then the synthesis of ATP NADH generated during Krebs cycle -> max _____ ATP NADH generated during glycolysis -> max ______ ATP FADH -> max ________ ATP The final tally 48. What is the maximum amount of ATP produced by aerobic respiration? 49. Why is that maximum rarely realized? Saving Kristine 50. Which of Kristine's symptoms is related to today's lecture? 51. What is your hypothesis concerning the cause of her symptoms? 52. Any suggestions how to cure her? 53. Why do mammals in cold environment produce less ATP per mole of glucose? 54. Why do infants produce less ATP per mole of glucose? More general 55. In summary, in humans, there are four major pathways for glucose metabolism - which are they? 56. What are the factors that determine which of the four is taken? 57. Compare photosynthesis and cellular respiration. Essay question Explain how ATP is produced in the inner mitochondrial membrane with the help of the respiratory chain.