MULTIPLE CHOICE QUESTIONS

Transcription

1 MULTIPLE CHOICE QUESTIONS 1. Most components of energy conversion systems evolved very early; thus, the most fundamental aspects of energy metabolism tend to be: A. quite different among a diverse group of organisms. B. very different among plants and animals. C. the same among the autotrophs but different among heterotrophs. D. the same among prokaryotes but different among eukaryotes. E. very similar in a wide range of different organisms. 2. The ultimate source of energy for almost all living organisms is: A. heat. B. glucose. C. carbohydrates. D. lipids. E. the sun. 3. Kilojoules are: A. units of heat energy. B. units of matter. C. units of work. D. units of kinetics. E. units of mechanical change. 4. An organism can exchange matter and energy with its surroundings. Thus, any change in an organism s energy content must be balanced by a corresponding change in the energy content of the surroundings. As such, an organism is referred to as: A. a closed system. B. an open system. C. a dynamic system. D. a thermally reactive system. E. a potential system. 5. Which word is defined by this statement: A measure of this disorder, or randomness? A. energy B. entropy C. enthalpy D. mass E. catabolism 7-1

2 6. Only 20% to 30% of the energy stored in the chemical bonds of gasoline molecules is transformed into mechanical energy; the other 70% to 80% is dissipated as waste heat. Which statement explains this phenomenon? A. The first law of thermodynamics. B. The second law of thermodynamics. C. When energy is converted from one form to another, some of the energy is converted into heat. D. Both the first and second laws of thermodynamics. E. Both the second law of thermodynamics, as well as the observation that the conversion of energy involves some energy being converted to heat. 7. In order for a cell to maintain a high degree of order, it must: A. constantly release energy. B. constantly produce energy. C. constantly destroy energy. D. constantly use energy. E. constantly increase energy. 8. The sum of all chemical activities taking place in an organism is: A. anabolism. B. catabolism. C. metabolism. D. dehydration synthesis. E. condensation reactions. 9. Which of the following accurately represents the relationship between the terms anabolism, catabolism, and metabolism? A. anabolism = catabolism B. metabolism = catabolism C. catabolism = anabolism + metabolism D. anabolism = catabolism + metabolism E. metabolism = catabolism + anabolism 10. Catabolic reactions involve the: A. breakdown of large organic molecules to simple building blocks. B. breakdown of life sustaining processes within cells. C. building up of complex organic molecules from simple building blocks. D. anabolic production of complex molecules. E. expenditure of energy. 11. Pathways that have an overall energy requirement are referred to as: A. catabolic reactions. B. anabolic reactions. C. energy-releasing reactions. D. energetically feasible reactions. E. reactions that will proceed spontaneously. 7-2

3 12. Every type of chemical bond contains a certain amount of energy. The total bond energy, which is essentially equivalent to the total potential energy of the system, is a quantity known as: A. entropy. B. kinetic energy. C. thermodynamic energy. D. enthalpy. E. free energy. 13. The equation, G = H - TS, predicts that: A. as entropy increases, the amount of free energy decreases. B. as enthalpy increases, the amount of free energy increases. C. as enthalpy decreases, the amount of entropy also decreases. D. metabolism decreases proportionately to anabolism. E. metabolism increases proportionately to catabolism. 14. An exergonic reaction is considered to be: A. spontaneous. B. potentially spontaneous. C. endergonic. D. nonspontaneous. E. energy requiring. 15. A reaction with a negative value of ΔG is referred to as an reaction. A. endergonic B. entropy C. exergonic D. enthalpy E. activation 16. An endergonic reaction can proceed only if it absorbs: A. more free energy than is released by a coupled exergonic reaction. B. less free energy than was released by a coupled endergonic reaction. C. less free energy than is released by a coupled exergonic reaction. D. the same amount of free energy that is absorbed by the enzymatic breakdown of proteins. E. energy from ADP, forming ATP. 17. In a reaction in which the rate of the reverse reaction is equal to the rate of the forward reaction, a state of is attained. A. total entropy B. enthalpy C. thermodynamics D. dynamic equilibrium E. product reversibility 7-3

4 18, 19. Use the figure to answer the corresponding questions. 18. Which of the following statements about the accompanying figure is true? A. The reactants have more free energy than the products. B. The products have more free energy than the reactants. C. The figure represents a spontaneous reaction. D. The figure represents an endergonic reaction. E. The reaction is endergonic, and also the products have more free energy than the reactants. 19. Which of the following conclusions can be accurately derived from the associated figure? A. ΔS is positive. B. ΔH equals zero. C. ΔG is positive. D. ΔG is negative. E. ΔT is negative. 20. Energy stored within the molecules of ATP is in the form of energy. A. kinetic B. heat C. potential D. nuclear E. light 21. Consider the following two chemical equations: A) glucose + fructose sucrose + H2O, ΔG = +27kJ/mole (or +6.5 kcal/mole) B) glucose + fructose + ATP sucrose + ADP + P i, ΔG = -5kJ/mole (or -1.2 kcal/mole) The free energy change difference between the chemical equations (A) and (B) above is accomplished by: A. a decrease in activation energy. B. combining two endergonic reactions. C. combining an endergonic and an exergonic reaction. D. combining two exergonic reactions. E. measuring the reaction rate. 22. Which of the following statements concerning ATP is FALSE? A. It is a nucleotide. B. It is called the energy currency of the cell. C. It contains phosphate groups joined in a series. D. It stores energy for long periods. E. It contains phosphate groups joined by unstable bonds. 7-4

5 23. Select the phosphorylation reaction: A. glucose + fructose sucrose + H 2 O B. glucose + ATP glucose-p + ADP C. glucose-p + fructose sucrose + P i D. glucose + glucose maltose E. None of these are phosphorylation reactions. 24. The maintenance of a high ATP to ADP ratio within cells ensures that: A. the hydrolysis of ADP to ATP will be strongly exergonic. B. the hydrolysis of ATP to ADP will be strongly exergonic. C. the hydrolysis of ATP to ADP will be strongly endergonic. D. the hydrolysis of ADP to ATP will be an energy releasing reaction. E. the conversion of ADP to ATP will proceed spontaneously. 25. The transfer of electrons from one compound to another is equivalent to transfer. A. heat B. oxygen C. enzymatic D. phosphorus E. energy 26. is a process where energy (as electrons) is released, whereas is a process where energy (as electrons) is accepted. A. Reduction; oxidation B. Enthalpy; entropy C. Entropy; enthalpy D. Oxidation; reduction E. Anabolism; catabolism 27. XH 2 + NAD + X + NADH + H +. In the preceding equation, NAD + is said to be: A. an enzyme. B. storing two hydrogen atoms. C. reduced. D. oxidized. E. a catalyst. 28. Select the reduced molecule: A. NAD + B. FAD C. NADH D. H - E. NADP Select the hydrogen acceptor molecule that stores electrons in the process of photosynthesis: A. nicotinamide adenine dinucleotide (NAD + ) B. nicotinamide adenine dinucleotide phosphate (NADP + ) C. flavin adenine dinucleotide (FAD) D. adenine triphosphate (ATP) E. adenine diphosphate (ADP) 7-5

6 30. FAD and cytochromes are classified as: A. hydrogen or electron acceptors. B. phosphate oxidizers. C. phosphate reducers. D. proteins that donate hydrogens or electrons. E. redox intermediate catalysts. 31. Because enzymes affect the speed of chemical reactions without being consumed, they are referred to as: A. hydrogen acceptors. B. activation energy. C. catalysts. D. cytochromes. E. transformation proteins. 32. Which of the following statements concerning enzymes is FALSE? A. Each enzyme has an optimal temperature. B. Each enzyme has an optimal ph. C. Most enzymes are highly specific. D. Some enzymes require cofactors. E. Most enzymes are RNA molecules. 33. Enzymes are important biological catalysts because they: A. supply the energy to initiate a biochemical reaction. B. increase the free energy of a biochemical reaction. C. lower the entropy of a biochemical reaction. D. decrease the enthalpy of a biochemical reaction. E. lower the activation energy of a biochemical reaction. 34. Which of the following statements concerning activation energy is FALSE? A. Exergonic reactions have an energy of activation. B. Endergonic reactions have an energy of activation. C. Enzymes lower a reaction s activation energy. D. Catalysts raise a reaction s activation energy. E. Activation energy is the energy required to break existing bonds. Use the figure to answer the corresponding questions, 35 &

7 35. The line on the graph labeled B represents the: A. activation energy with an enzyme. B. activation energy without an enzyme. C. free energy of the reactants. D. change in entropy. E. change in enthalpy. 36. The line on the graph labeled C represents the: A. activation energy with an enzyme. B. activation energy without an enzyme. C. change in free energy. D. change in entropy. E. change in enthalpy. 37. Parts of the enzyme molecule that interact with a substrate are called: A. cofactors. B. active sites. C. induced-fit models. D. orientation sites. E. reaction sites. 38. The substance on which an enzyme acts is called the: A. substrate. B. product. C. ATP. D. free energy. E. cofactor. 39. What refers to the situation in which the binding of a substrate to the enzyme causes a change in the enzyme s shape, facilitating an enzyme s function? A. active site B. cofactor C. activation energy D. induced fit E. allosteric inhibition 40. Hydrolases are one important class of enzyme that function to catalyze: A. splitting a molecule using water. B. conversions between isomers. C. reactions in which double bonds are formed. D. oxidation-reduction reactions. E. None of these. 7-7

8 41. Which refers to an organic, nonpolypeptide compound that binds to the apoenzyme and serves as a cofactor? A. coenzyme B. catalyst C. substrate D. mineral E. allosteric regulator 42. Which of the following does not represent a method by which cells regulate enzyme activity? A. controlling the intracellular concentration of the enzyme B. feedback inhibition of enzymes C. the binding of allosteric regulators to allosteric sites on the enzyme D. differential gene expression of the genes that produce enzymes E. heat denaturation of the enzyme 43. Select the enzyme that does not match the reaction: A. sucrase splits sucrose into glucose and fructose B. lipase breaks ester linkages C. phosphatase removes phosphate groups D. urease converts urea to ammonia and CO 2 E. kinase breaks peptide bonds 44. If one continues to increase the temperature in an enzyme-catalyzed reaction, the rate of the reaction: A. does not change. B. increases and then levels off. C. decreases and then levels off. D. increases and then decreases rapidly. E. decreases and then increases rapidly. 45. You conduct an experiment in which you add increasing amounts of substrate to an enzyme solution and then measure the resulting reaction rate. You graph your results, plotting the rate of the reaction on the Y-axis versus substrate concentration on the X-axis. What do you conclude from your graph? A. The reaction rate is directly proportional to substrate concentration. B. The reaction rate is independent of substrate concentration. C. The reaction rate increases but then decreases, forming a bell-shaped curve. D. The reaction rate decreases with increasing substrate concentration. E. The reaction rate increases with increasing substrate concentration up to a point, above which the rate remains constant. 7-8

9 46. An allosteric enzyme: A. has an active site that binds to the substrate and an allosteric site that binds to the product. B. allows the movement of molecules and ions from one part of the cell to another. C. catalyzes both oxidation and reduction reactions. D. raises a reaction s activation energy so that the rate of the reaction declines. E. allows a substance other than the substrate to bind to the enzyme, thereby activating or inactivating it. 47. Competitive inhibitors inhibit biochemical reactions in such a way as to seemingly: A. increase the concentration of substrate. B. reduce the concentration of enzyme. C. increase the concentration of enzyme. D. reduce the concentration of substrate. E. denature the enzyme. 48. Penicillin is a drug that acts by: A. irreversibly inhibiting transpeptidase. B. reversibly inhibiting transpeptidase. C. competitively inhibiting transpeptidase. D. noncompetitively inhibiting transpeptidase. E. None of these. DISCUSSION OR THOUGHT QUESTIONS- Pick ONE of the following questions and type your answer on a separate sheet of paper. 1. Living cells maintain biochemical reactions far from equilibrium conditions. They do this by constantly manipulating the concentrations of reactants and products. Why is it important that a state far from equilibrium be maintained? 2. How is it possible for an enzyme to lower the required energy of activation for a reaction? 3. It is a fact that enzymes are highly specific and will only catalyze one or a few reactions. Can you think of a benefit that is derived from such specificity? (i.e. What would happen if most biochemical reactions were catalyzed by the same enzyme?) 7-9