Practice Questions Set 7 Cellular Respiration

QUESTION

Practice Questions Set 7Cellular Respiration1. Review the reactions in glycolysis (do not memorize the reactions). Mark the “energyinvestment phase” and “energy payoff/harvest phase” of glycolysis on the diagram.Where is ATP used? Where is ATP produced? Where is NADH produced?2. The molecule that functions as the reducing agent (electron donor) in a redox or oxidationreduction reactionA) gains electrons and gains energy.B) loses electrons and loses energy.C) gains electrons and loses energy.D) loses electrons and gains energy.Review the principle of Redox.3. Explain how oxidation of methane is carried out through relative loss of electrons (see figurefrom textbook). 8-2 p163 Memorize this figure4. Where in the cell does each of the following take place? Glycolysis, Pyruvate Oxidation,Citric Acid Cycle, Electron Transport / Oxidative Phosphorylation?5. Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present orabsent?A) electron transportB) glycolysisC) the citric acid cycleD) oxidative phosphorylationE) chemiosmosis6. Explain your answer to the previous question.7. The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the freeenergy for the reduction of NAD+ to NADH is +53 kcal/mole. Why are only two moleculesof NADH formed during glycolysis when it appears that as many as a dozen could beformed?Consider what comes out of the reaction as a net product. Where is the rest of the potentialenergy?8. Review the structure of pyruvate. Pyruvate has to enter the mitochondria in order to enter thecitric acid cycle. Will pyruvate cross the lipid bilayer membrane easily? Explain.Is pyruvate hydrophilic or hydrophobic? Will it cross the lipid bilayer with its hydrophobicinterior made of fatty acid tails? Or will it need the help of a transport protein (regardless ofwhether it’s active or passive transport)?9. Consider the cotransport proteins involved in bringing Pyruvate into the matrix of themitochondria. In the absence of oxygen, why won’t pyruvate enter the mitochondria?Consider the proton gradient across the inner membrane, and the role of oxygen in establishing1this gradient.Refer to the figure below to answer the following questions.The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence.Each step is lettered. Use these letters to answer the questions.10. In which step is an inorganic phosphate added to the reactant?Look for the addition of the phosphate group indicated as a P inside a circle.11. In addition to ATP, what are the end products of glycolysis?Consider what comes out of the reaction as a net product.12. Review Figure 8.8 in the textbook. Mark the energy investment and energy harvest steps.13. Review Figure 8.8 in the textbook. Explain why step 6 is a redox reaction.14. Review Figure 8.8 in the textbook. Explain why steps 7 and 10 are considered substratelevel phosphorylation.What provides the phosphate for synthesis of ATP from ADP?15. Review the citric acid cycle. How many carbon atoms are fed into the citric acid cycle as aresult of the oxidation of one molecule of glucose?A) 2B) 4C) 6D) 8E) 10216. In the diagram of the citric acid cycle, circle and identify the step that shows substrate-levelphosphorylation.What provides the phosphate for synthesis of ATP from ADP?17. Review the citric acid cycle. Explain why step 6 is a redox reaction.Gaining or losing hydrogens (not just electrons)…18. Review the citric acid cycle. Explain why step 8 is a redox reaction.What happens to the hydroxyl group? To NAD+?19. Review the citric acid cycle. Explain what happens if you add an inhibitor that inhibitsmalate dehydrogenase.20. Review the figure detailing electron transport in mitochondria. Where are iron/sulfurproteins found in mitochondria?21. Review the figures detailing the experiments in support of chemiosmosis. What is the bigquestion being asked? What are the two alternative hypotheses? The experimentalpredictions? What is the control treatment?22. What would you do using the system used by Racker and Stoeckenius to answer thisquestion: Is ATP synthase required for ATP synthesis? Design the experiment.23. Both FADH2 and NADH donate electrons to the electron transport chain. Which does it at alower energy level?24. During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesisof the water come from?A) carbon dioxide (CO2)B) glucose (C6H12O6)C) molecular oxygen (O2)D) pyruvate (C3H3O3-)E) lactate (C3H5O3-)See the textbook or lecture slides.25. Review the citric acid cycle. How many molecules of ATP, NADH, and FADH2 aregenerated in the citric acid cycle as a result of the oxidation of one molecule of pyruvate?26. Review the slides for electron transport in the mitochondria. In your own words explain howdonation of electrons by NADH and FADH2 to the ETC leads to the synthesis of ATP.27. Review the slides for electron transport in the mitochondria. It is possible to prepare vesiclesfrom portions of the inner membrane of the mitochondrial components. For oxidativephosphorylation to be carried on by this isolated inner membrane with its protein complexesintact, we must provide the required substrates. What are these substrates?List all of the materials that are supplied on the matrix side of the membrane.328. Review the slides for electron transport in the mitochondria from lecture notes. Mark thesteps that contribute to the formation of the proton gradient across the membrane.Consider both movement of protons across the membrane and reactions that remove protonsfrom the matrix, synthesis of water (not the ones that add protons to the matrix).29. You have identified a new protein that might act as a cotransporter that moves pyruvateactively across a membrane using the energy released from the movement of protons downtheir gradient. We want to know whether this protein is in fact a pyruvate-protoncontransporter to transport pyruvate against its gradient across a lipid membrane. Design anexperiment to figure this out. To simplify the experimental design you can use an artificialvesicle (simple lipid bilayer) because you can insert whatever protein you like into the lipidbilayer of the artificial vesicle. You do not need to describe details of methods. Forexample, you can simply state we will measure the voltage across the membrane withoutexplaining how you will do that (if that applied to your experiment). Describe the elementsof experimental design needed for this new experiment: null and alternative hypotheses,experimental details including independent and dependent and standardized variables, levelsof treatment, and experimental prediction.30. Dinitrophenol is an uncoupler. In general terms, what does an uncoupler do? How would itaffect electron transport in the mitochondria? How would it affect ATP synthesis in themitochondria? Why would it be even considered as a potential “diet pill”?Uncouplers dissipate the proton gradient across the membrane and uncouple electron transportfrom ATP synthesis…31. Cyanides attach to the iron within cytochrome c oxidase and inhibit its activity. What wouldthat do to electron transport in the mitochondria? To the proton gradient? To ATPsynthesis? Why would that make cyanides poisonous to us? Explain.If cytochrome c oxidase cannot oxidize cytochrome c, what does that mean for electron transportin the mitochondria? If electrons are not moving from complex to complex, what does that do tothe establishment of a proton gradient? ATP synthesis?32. Why is it important for complexes I, III, and IV in the mitochondria to be transmembraneproteins while complex II is not?33. Plants make and store cyanide in their cells. What is the purpose of cyanide in the plants?34. If you subject plant mitochondria to cyanide, the plants survive because of the presence ofthe alternative oxidase that allows them to bypass complexes III and IV. As far as we know,is this a defensive mechanism that has evolved to protect the plants against cyanidepoisoning? Explain.Is a plant likely to be poisoned by cyanide?!35. Plants have an alternative oxidase that allows them to bypass complexes III and IV. Thismeans electrons from ubiquinone go to this alternative oxidase, which then passes theelectrons to oxygen reducing it to water. Compare the proton gradient established across theinner mitochondrial membrane, the relative amount of ATP synthesized, and the energyreleased as heat when this alternative oxidase is used as opposed to when the normal electron4transport pathway (including complexes III, IV, and cytochrome c) is used.Consider the role of complexes III and IV in establishing the proton gradient and everything thatfollows from that. If electrons are going from ubiquinone to the alternative oxidase and then tooxygen, what happens to the proton gradient? To the number of ATP molecules produced perpyruvate?36. Plants have an alternative oxidase that allows them to bypass complexes III and IV. Thisallows them to raise their tissue temperatures under certain conditions. Describe twoexamples where this could be useful to the plants.Recall the skunk cabbage melting snow (why is that important?). Some plants like voodoo liliesvolatilize chemicals from their flowers (why is that important?)37. An organism has a mutation in the pyruvate symporter in the mitochondria. The mutationmakes the symporter 50% as efficient as the normal protein in transporting pyruvate into themitochondria. What would be the consequences of this mutation to the organism?38. In the absence of oxygen fermentation must happen, otherwise glycolysis will stop. This isregardless of whether it is lactic acid fermentation or alcohol fermentation that is used.Explain why (refer to figures, but do not memorize them).NAD+ is needed for glycolysis…39. Review the figures for fermentation. In each, explain where the redox reaction is. Make sureto identify the functional groups in the substrate and the final product in each.40. Why does yeast-based dough rise? Think CO2.41. Yeast is a facultative anaerobe. What does that mean?5

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