Chemistry and Biochemistry 153A Spring 2011 Final Exam Instructions: (Note that changes or additions to the usual instructions have been underlined.) You will have 3 hours to complete the exam. You may use a pencil (recommended) or blue or black ink pen to write your answers. Other color inks will not be graded. Your choice of writing utensil will not affect your ability to request a regrade. Only answers on the separate answer sheets, in the indicated space, will be graded; writing anywhere else will be ignored. Be sure to write your name and your discussion board username, if you have one, on the answer sheet. Do not write in the score boxes on your answer sheet; you will be docked points if you do. For answers with a word or sentence limit, words beyond this limit will not be read or graded. For short- or multi-answer questions, including irrelevant or wrong information or selections in your answer will cause you to lose points. Write legibly. If the grader cannot read your answer, you won’t get credit. Items you may have on your desk: - non-programmable scientific calculator, without its case or cover - writing utensil(s) - student ID ALL other items must be placed into a bag, which must be zipped up or closed and pushed completely under your chair. No hats, hoods, earphones, or cellphones are allowed. If you continue to write after ‘time’ is called, your exam will be taken and docked 10 points. Questions are printed on both sides, as are the two colored answer sheets. Be sure you’ve answered all of the questions! Note – although each half of the exam is worth 100 points, you may find the second (cumulative) half to be more involved, so budget your time accordingly. Exam pages: 2-8: Questions 9-13: Help/scratch pagesChem 153A Final Exam, Spring 2011 Answer Sheet 1 (BLUE) Page 2 of 8 Part 1 – New Material (100 points) 1. (8) Consider noncompetitive inhibition: a. (5) Which of the following relationships can indicate noncompetitive inhibition? Choose all that apply. A. ܭ> ܭ B. ܭ< ܭ C. ܭ= ܭ D. ܸ௫> ܸ௫ E. ܸ௫< ܸ௫ F. ܸ௫= ܸ௫ G. ܭூ> ܭூ′ H. ܭூ< ܭூ′ I. ܭூ= ܭூ′ b. (3) Noncompetitive inhibition is much less common than other types of reversible inhibition. Why? Choose the best explanation. A. Most inhibitors that bind in an alternate site are allosteric inhibitors. B. Inhibitor binding is usually influenced by the binding of substrate. C. Inhibitors usually have highest affinity for the free enzyme. D. Noncompetitive inhibition is actually a type of competitive inhibition. 2. (2) Complete the following sentence: TPP aids in the decarboxylation of _________ acids 3. (6) For each of the following parts, answer by giving either the name(s) of the enzyme(s) or the reactants and products. a. Which reaction(s) of aerobic metabolism use(s) TPP? b. Which reaction(s) of anaerobic metabolism use(s) TPP? 4. (5) Why do cells have multiple different redox currencies? Determine whether each of the following explanations is correct or incorrect. (Circle your choice for each.) a. To enhance metabolic efficiency by limiting the number of different redox reactions. b. To oxidize or reduce compounds of differing reduction potential. c. To allow transfers of different numbers of electrons. d. To link catabolic and anabolic pathways. e. To keep separate pools of reduced and oxidized currencies. 5. (12) Consider the aldol cleavage reaction catalyzed by aldolase. a. (2) Write a balanced equation for this reaction. (Abbreviations are OK.) b. (5) ∆G′° = +22.8 kJ/mol for this reaction. However, this reaction is readily reversible in the cell, due to sub-molar concentrations of reactant(s) and product(s). If the concentrations of all reactants and products were equal, calculate what this concentration would need to be for this reaction to go in the forward direction (in human muscle cells). Show your work. c. (3) Other than low reactant and product concentrations, what other factor or process promotes this reaction going forward in glycolysis? Briefly explain in 25 words or fewer.Chem 153A Final Exam, Spring 2011 Answer Sheet 1 (BLUE) Page 3 of 8 6. (10) Consider the enzyme glycogen phosphorylase. a. (2) What is the significance of this enzyme? (What is its important role?) Answer in 10 words or fewer. b. (3) How is this enzyme regulated in the cell? Choose all that apply. A. Feedback inhibition B. Product inhibition C. Substrate concentration D. Binding of allosteric effectors E. Covalent modification c. (5) For each of the following compounds, state whether increasing its concentration would be likely to increase or decrease the activity of glycogen phosphorylase. (The effect may be direct or indirect.) A. glucose B. glucose-1-phosphate C. ATP D. AMP E. NADH 7. (6) True or false? (1 point each) a. Specific transporters are necessary to move small metabolites across both mitochondrial membranes. b. Pyruvate dehydrogenase uses 5 cofactors: TPP, lipoic acid, Coenzyme Q, FAD, and NAD+. c. Many vitamins are essential because of their use in enzyme cofactors. d. Glycolysis is an anaerobic process. e. In eukaryotes, fermentation occurs in mitochondria. f. In eukaryotes, aerobic metabolism occurs in mitochondria. 8. (7) Given the starting and ending structures, show how triosephosphate isomerase catalyzes the isomerization of DHAP. Include curved arrows to show electron movements, generic enzyme groups involved in the catalysis, and the structure of the intermediate that is formed. C OHHC OC OHHPO32-CHC OC OHHPO32-OHHH 9. (5) A reaction that is favorable in the forward direction (having a negative ∆G) is unfavorable in the reverse direction (having a positive ∆G of equal magnitude). The same is true for a pathway; if it is favorable in the forward direction, it is equally unfavorable in the reverse direction. So how can glycolysis and gluconeogenesis be simultaneously favorable (both having negative ∆G) in a cell? Briefly explain in 35 words or fewer.Chem 153A Final Exam, Spring 2011 Answer Sheet 1 (BLUE) Page 4 of 8 10. (3) You have been growing a culture of yeast in an anaerobic chamber on a glucose food source. What effect would you expect to see if oxygen is added to
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