Name: __________________________________ NetID:_________________________ 1 MCB 450 Exam III April 9, 2015 Form A Choose the BEST answer from the available choices. Only non-graphing calculators are permitted for use on this exam. Extra blank pages are provided at the end of the exam booklet (pgs.14-15) for your calculations. Part I: 29 Multiple-choice questions. Each question is worth 4 points for a total of 116 possible points. Record all of your answers on the provided scantron sheet. 1. The coenzyme A is a carrier for acyl groups. The acyl group is linked to coenzyme A via a/an_______. a. thioester bound b. phosphoester bound c. imidazole ring d. oxygen ester bound e. hydrogen bound 2. All of the following processes are characteristics of anabolism EXCEPT: a. Proteins are assembled from amino acids. b. Carbon molecules are oxidized. c. ATP hydrolysis is used as a source of energy. d. NADP+ is used to deliver hydride ions. e. Water is released during formation of new covalent bonds. 3. Which of the following factors does NOT contribute to the high phosphoryl-transfer potential of ATP, giving it a ∆G°ʹ = - 30.5 kJ/mol? a. Increase in entropy b. Resonance stabilization c. Electrostatic repulsion d. Stabilization due to hydration e. Small activation energyName: __________________________________ NetID:_________________________ 2 4. Transfer of the phosphoryl group from phosphoenolpyruvate (PEP) to ADP is an example of ___________. a. a mutase reaction b. isomerization c. a dehydrogenase reaction d. substrate-level phosphorylation e. a lyase reaction 5. Which of the following statements about the structure of ATP is CORRECT? a. It contains three phosphoanhydride bonds. b. It contains two phosphate ester bonds. c. The sugar moiety is linked to the triphosphate by a phosphate ester bond. d. The triphosphate is linked to carbon 1 of the sugar moiety. e. The sugar moiety is ribulose. 6. The adjoining graph shows muscle phosphofructokinase (PFK) activity as a function of ATP concentration in the presence of a constant concentration of fructose 6-phosphate. Explain the effect of ATP on the PFK activity: a. ATP has a heterotropic effect at low concentration. b. ATP has both homotropic and heterotropic effects. c. At high ATP, PFK is phosphorylated. d. ATP is unable to bind to the allosteric site on PFK at high concentration. e. All of the above explanations are true.Name: __________________________________ NetID:_________________________ 3 7. Which of the following statements can explain why the rate of glycolysis in the liver is only significant under conditions of high blood sugar levels? a. Glucokinase has a Km, which is much lower than that of the muscle hexokinase 1. b. GLUT 4 receptors only operates at low blood sugar levels. c. Glucokinase is inhibited by high glucose concentration. d. Glucokinase will operate at half Vmax only when the blood sugar levels is above that of normal blood sugar levels. e. Answer choices A and B are both correct. 8. The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except: a. Substrate-level phosphorylation. b. Generation of a reaction intermediate that is covalently bound to the enzyme via a thioester bond. c. Oxidation of NADH to NAD+. d. Formation of 1,3-bisphosphoglycerate. e. Utilization of Pi. 9. The conversion of 1 mole of fructose 1,6 bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of: a. 1 mol of NAD+ and 2 mol of ATP b. 1 mol of NADH and 1 mol of ATP c. 2 mol of NADH and 2 mol of ATP d. 2 mol of NADH and 4 mol of ATP e. 2 mol of NAD+ and 4 mol of ATP 10. Which of the following enzymes is most active when phosphorylated? a. Protein kinase A b. Fructose-1,6-bisphosphatase c. Hexokinase d. Pyruvate kinase e. Fructose-2,6-bisphosphataseName: __________________________________ NetID:_________________________ 4 11. Which of the following enzymes is used by the gluconeogenesis pathway to bypass an irreversible reaction in glycolysis? a. Phosphoglycerate kinase b. Aldolase c. Enolase d. Fructose 1,6 bisphosphatase e. Phosphofructokinase 12. Gluconeogenesis takes place during exercise, which seems counterintuitive. Why would an organism synthesize glucose and, at the same time, use glucose to generate energy? a. The increased glycolysis in response to exercise generates ATP, which stimulates gluconeogenesis in muscles. b. The increased glycolysis in muscles generates lactate, which stimulates gluconeogenesis in the liver. c. Epinephrine released during exercise stimulates gluconeogenesis in muscles. d. Ca2+ released by muscle contraction stimulates gluconeogenesis in muscles. e. The increased glycolysis in muscles generates high levels of alanine, which stimulate gluconeogenesis. 13. Which of the following statement is TRUE regarding the reciprocal regulation of glycolysis and gluconeogenesis by the bifunctional enzyme phosphofructokinase 2/fructose 2,6 bisphosphatase? a. Levels of fructose 2,6 bisphosphate are decreased in response to high cAMP levels. b. Phosphorylation of the bifunctional enzyme inhibits fructose 2,6 bisphosphatase activity. c. Insulin stimulate the phosphorylation of the bifunctional enzyme. d. Low blood sugar activates the phosphoprotein phosphatase resulting in dephosphorylation of the bifunctional enzyme. e. None of the above choices are true.Name: __________________________________ NetID:_________________________ 5 14. The non-oxidative stage of the pentose phosphate pathway: a. produces NADPH and releases CO2. b. consists entirely of near-equilibrium reversible reactions. c. contains two reactions whose enzymes are allosterically inhibited by NADPH. d. consumes four ATP molecules. e. uses NADPH to generate a 5-carbon sugar. 15. The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of: a. 6 mol of pentose, 4 mol of NADPH, and 8 mol of CO2. b. 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2. c. 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2. d. 4 mol of pentose, 3 mol of NADPH, and 3 mol of CO2. e. 6 mol of pentose, 6 mol of NADPH, and 6 mol of CO2. 16. Which of the following reactions is catalyzed by a transketolase in the pentose phosphate pathway? I. fructose-6-P + glyceraldehyde-3-P ↔ xylulose-5-P + erythrose-4-P II. erythrose-4-P +
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