1Chapter 5: The Flow of EnergyMultiple-Choice Questions1. Introduction; p. 94; easy; ans: eOf the total solar energy that reaches the Earth, ______ percent is captured by the cells of photosynthetic organisms.a. about 50b. about 20c. about 10d. about 5e. less than 12. The Laws of Thermodynamics; p. 95; moderate; ans: cThe energy of a system is defined as:a. the amount of caloric present.b. the amount of ATP present.c. its capacity to do work.d. the sum total of its chemical bonds.e. the speed at which its atoms and molecules move.3. The Laws of Thermodynamics; p. 95; moderate; ans: dAccording to the first law of thermodynamics, the total energy of ______ is ______.a. a system; constantb. a system; changeablec. the surroundings; constantd. the universe; constante. the universe; changeable4. The Laws of Thermodynamics; p. 95; easy; ans: cThe first law of thermodynamics states that:a. all natural processes proceed in such a direction that the disorder of the universe increases.b. the activation energy of chemical reactions is raised by enzymes.c. energy can be changed from one form to another, but it cannot be created or destroyed.d. ΔG = ΔH - TΔS.e. ATP is the energy currency of the cell.5. The Laws of Thermodynamics; p. 95; moderate; ans: dWhich of the following is NOT an example of potential energy? a. A charged flashlight batteryb. A boulder at the top of a hillc. A tank of gasolined. Water at the bottom of a waterfalle. An apple on a branch56 Chapter 5 The Flow of Energy6. The Laws of Thermodynamics; p. 96; easy; ans: aThe first law of thermodynamics states that the total energy of a system and its surroundings after an energy conversion is ______ the total energy before the conversion.a. equal tob. greater than or equal toc. greater thand. less than e. less than or equal to7. The Laws of Thermodynamics; p. 96; easy; ans: bOne way of stating the second law of thermodynamics is:a. although energy can be changed from one form to another, it can be neither created nor destroyed.b. the entropy of the universe is increasing.c. free energy is equal to the total potential energy minus the entropy.d. enthalpy is the total potential energy of a system.e. the activation energy of a reaction is always positive.8. The Laws of Thermodynamics; p. 96; easy; ans: dThe second law of thermodynamics states that if no energy enters or leaves the system under study, the potential energy of the final state will be______ the potential energy of the initial state.a. equal tob. greater than or equal toc. greater thand. less than e. less than or equal to9. The Laws of Thermodynamics; p. 96; moderate; ans: a An exergonic reaction: a. is a reaction in which the potential energy of the final state is less than that of the initial state.b. does not take place spontaneously.c. requires an input of energy from the outside.d. has a positive free-energy change.e. has a positive ΔG value.10. The Laws of Thermodynamics; p. 97; difficult; ans: cΔH refers to the:a. heat released in an exergonic reaction.b. heat released in an endergonic reaction.c. change in enthalpy.d. change in entropy.e. exact change in potential energy.11. The Laws of Thermodynamics; p. 97; easy; ans: dEntropy refers to the ______ of a system.a. heat content b. free energyc. potential energyd. disorder or randomness e. kinetic energy12. The Laws of Thermodynamics; p. 97; easy; ans: bΔG refers to the change in ______ of the system.a. the total heat contentb. free energyc. entropyd. enthalpye. the randomness13. The Laws of Thermodynamics; p. 97; easy; ans: dWhich of the following equations relating enthalpy, entropy, and free energy is correct?a. ΔS = ΔH - T ΔGb. ΔH = ΔG - T ΔSc. ΔS = ΔG + T ΔHd. ΔG = ΔH - T ΔSe. ΔG = ΔH + T ΔS14. The Laws of Thermodynamics; p. 97; moderate; ans: eIn all naturally occurring processes:a. ΔH is positive.b. ΔH is negative.c. ΔS is positive.d. ΔS is negative.e. ΔG is negative.15. The Laws of Thermodynamics; p. 97; easy; ans: cThe second law of thermodynamics states that all naturally occurring processes:a. are exothermic.b. are endothermic.c. are exergonic.d. are endergonic.e. proceed with an increase in entropy.58 Chapter 5 The Flow of Energy16. The Laws of Thermodynamics; pp. 97–98; moderate; ans: bWhich of the following statements about living cells is FALSE?a. They expend energy to maintain order.b. They are at equilibrium with their surroundings.c. They are open systems.d. They transform energy.e. As they transform energy, they dissipate heat.17. Oxidation-Reduction; p. 98; easy; ans: aOxidation is defined as the:a. loss of electrons.b. loss of protons.c. loss of electrons and protons.d. gain of electrons.e. gain of protons.18. Oxidation-Reduction; p. 98; moderate; ans: aIn biological reactions, when a molecule is oxidized it ______ an electron and a(n) ______.a. loses; protonb. gains; protonc. loses; oxygen atomd. gains; oxygen atome. loses; neutron19. Oxidation-Reduction; p. 99; easy; ans: bIn the following reaction, which molecule is oxidized?glucose + oxygen → carbon dioxide + watera. Glucoseb. Oxygenc. Carbon dioxided. Watere. Carbon dioxide and water are reduced.20. Oxidation-Reduction; p. 99; moderate; ans: bDuring the oxidation of glucose in the cell, most of the energy is released:a. all at once.b. in small amounts.c. via mechanisms that require many kinds of molecules.d. via mechanisms that result in high temperatures.e. in a way that requires the input of 686 kilocalories of energy.21. Enzymes; p. 100; easy; ans: dAn enzyme:a. is typically effective only in large amounts.b. is a type of carbohydrate.c. raises the activation energy of its reaction.d. functions as a catalyst.e. is permanently altered during the course of its reaction.22. Enzymes; p. 100; easy; ans: bMost enzymes are:a. RNA molecules.b. proteins.c. carbohydrates.d. lipids.e. DNA molecules.23. Enzymes; p. 100; easy; ans: cA substrate binds to its enzyme at a location called the ______ site.a. coenzymeb. substratec. actived. polypeptidee. cofactor24. Enzymes; p. 101; moderate; ans: aA negatively charged portion of a substrate molecule would most likely fit into a ______ region of itsenzyme’s active site.a. positively chargedb. negatively chargedc. hydrophilicd. hydrophobice. polar25. Cofactors in Enzyme Action; p. 101; moderate; ans: bThe general name for a nonprotein component required by some enzymes is a:a. metal ion.b. cofactor.c. substrate.d. prosthetic group.e. coenzyme.60 Chapter 5 The