Biology, 7e (Campbell)
Chapter 8: An Introduction to Metabolism

Chapter Questions

1)  Which of the following describe(s) some aspect of metabolism? 
A) synthesis of macromolecules 
B) breakdown of macromolecules 
C) control of enzyme activity 
D) A and B only 
E) A, B, and C 
Answer: E 
Topic: Concept 8.1
Skill: Knowledge

2)  Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? 
A) catalysis 
B) metabolism 
C) anabolism 
D) dehydration 
E) catabolism 
Answer: E 
Topic: Concept 8.1
Skill: Knowledge

3)  Which of the following statements correctly describe(s) catabolic pathways? 
A) They do not depend on enzymes. 
B) They consume energy to build up polymers from monomers. 
C) They release energy as they degrade polymers to monomers. 
D) They lead to the synthesis of catabolic compounds. 
E) both A and B 
Answer: C 
Topic: Concept 8.1
Skill: Knowledge

4)  Which of the following is (are) true for anabolic pathways? 
A) They do not depend on enzymes. 
B) They are highly regulated sequences of chemical reactions. 
C) They consume energy to build up polymers from monomers. 
D) They release energy as they degrade polymers to monomers. 
E) both B and C 
Answer: E 
Topic: Concept 8.1
Skill: Knowledge

5)  Which of the following is a statement of the first law of thermodynamics? 
A) Energy cannot be created or destroyed. 
B) The entropy of the universe is decreasing. 
C) The entropy of the universe is constant. 
D) Kinetic energy is stored energy that results from the specific arrangement of matter. 
E) Energy cannot be transferred or transformed. 
Answer: A 
Topic: Concept 8.1
Skill: Knowledge

6)  The first law of thermodynamics states that energy can be neither created nor destroyed.  For living organisms, which of the following is an important consequence of the first law? 
A) The energy content of an organism is constant. 
B) The organism ultimately must obtain all of the necessary energy for life from its environment. 
C) The entropy of an organism decreases with time as the organism grows in complexity. 
D) Organisms are unable to transform energy. 
E) Life does not obey the first law of thermodynamics. 
Answer: B 
Topic: Concept 8.1
Skill: Application

7)  According to the first law of thermodynamics, 
A) the universe loses energy because of heat production. 
B)  systems rich in energy are intrinsically unstable and will give up energy with time. 
C) energy can be neither created nor destroyed.  
D) A and B only 
E) A, B, and C 
Answer: C 
Topic: Concept 8.1
Skill: Comprehension

8)  Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism.  How does this relate to the second law of thermodynamics? 
A) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time. 
B) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is balanced by an increase in the entropy of the universe. 
C) Living organisms do not follow the laws of thermodynamics. 
D) As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth. 
E) Living organisms are able to transform energy into entropy. 
Answer: D 
Topic: Concept 8.1
Skill: Application

9)  Which of the following statements about metabolism is incorrect? 
A) Metabolism is an emergent property of life at the level of organisms. 
B) Metabolism manages the utilization of materials and energy resources. 
C) The uptake of water associated with the hydrolysis of biological polymers is part of metabolism. 
D) Metabolism depends on a constant supply of energy. 
E) None of these statements about metabolism is incorrect. 
Answer: A 
Topic: Concept 8.1
Skill: Comprehension

10)  Whenever energy is transformed, there is always an increase in the 
A) free energy of the system. 
B) free energy of the universe. 
C) entropy of the system. 
D) entropy of the universe. 
E) enthalpy of the universe. 
Answer: D 
Topic: Concept 8.1
Skill: Comprehension

11)  Which of the following statements is a logical consequence of the second law of thermodynamics? 
A) If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe. 
B) If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe. 
C) Every energy transfer requires activation energy from the environment. 
D) Every chemical reaction must increase the total entropy of the universe. 
E) Energy can be transferred or transformed, but it cannot be created or destroyed. 
Answer: D 
Topic: Concept 8.1
Skill: Comprehension

12)  Which of the following statements correctly describe(s) some aspect of energy in living organisms? 
A) Living organisms can convert energy among several different forms. 
B) Living organisms can use energy to do work. 
C) Organisms expend energy in order to decrease their entropy 
D) A and B only 
E) A, B, and C 
Answer: E 
Topic: Concept 8.1
Skill: Comprehension

13)  Which of the following statements is not representative of the second law of thermodynamics? 
A) Conversion of energy from one form to another is always accompanied by some loss of free energy. 
B) Heat represents a form of energy that cannot be used by most organisms to do work. 
C) Without an input of energy, organisms would tend towards increasing entropy. 
D) Cells require a constant input of energy to maintain their high level of organization. 
E) Every energy transformation by a cell decreases the entropy of the universe. 
Answer: E 
Topic: Concept 8.1
Skill: Comprehension

14)  Which of the following forms of energy is least available to accomplish cellular work? 
A) light energy 
B) electrical energy 
C) thermal energy (heat) 
D) mechanical energy 
E) potential energy 
Answer: C 
Topic: Concept 8.1
Skill: Knowledge

15)  Which of the following types of reactions would decrease the entropy within a cell? 
A) dehydration reactions 
B) hydrolysis 
C) respiration 
D) digestion 
E) catabolism 
Answer: A 
Topic: Concept 8.1
Skill: Comprehension

16)  According to the second law of thermodynamics, which of the following statements is incorrect? 
A) The synthesis of large molecules from small molecules is exergonic. 
B) Earth is an open system. 
C) Life exists at the expense of energy derived from its environment. 
D) A living cell can never function as a closed system. 
E) Every chemical reaction in a cell results in a loss of free energy. 
Answer: A 
Topic: Concept 8.1
Skill: Comprehension

17)  The organization of organisms has become increasingly complex with time.  This statement 
A) is consistent with the second law of thermodynamics. 
B) requires that due to evolution, the entropy of the universe increased. 
C) is based on the fact that organisms function as closed systems. 
D) A and B only 
E) A, B, and C 
Answer: A 
Topic: Concept 8.1
Skill: Comprehension

18)  The mathematical expression for the change in free energy of a system is:  ΔG = ΔH – TΔS.  Which of the following is (are) incorrect? 
A) ΔS is the change in entropy, a measure of randomness. 
B) ΔH is the change in enthalpy, the energy available to do work. 
C) ΔG  is the change in free energy. 
D) T is the absolute temperature. 
E) both A and B 
Answer: B 
Topic: Concept 8.2
Skill: Knowledge

19)  What is the change in free energy of a system at chemical equilibrium? 
A) slightly increasing 
B) greatly increasing 
C) slightly decreasing 
D) greatly decreasing 
E) no net change 
Answer: E 
Topic: Concept 8.2
Skill: Knowledge

20)  Which of the following is true for all exergonic reactions? 
A) The products have more total energy than the reactants. 
B) The reaction proceeds with a net release of free energy. 
C) Some reactants will be converted to products. 
D) A net input of energy from the surroundings is required for the reactions to proceed. 
E) The reactions are nonspontaneous. 
Answer: B 
Topic: Concept 8.2
Skill: Comprehension

21)  Chemical equilibrium is relatively rare in living cells.  Which of the following could be an example of a reaction at chemical equilibrium in a cell? 
A) a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium 
B) a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings 
C) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment 
D) a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive 
E) There is no possibility of having chemical equilibrium in any living cell. 
Answer: D 
Topic: Concept 8.2
Skill: Application

22)  Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein? 
A) +ΔH, +ΔS, +ΔG 
B) +ΔH, -ΔS, -ΔG 
C) +ΔH, -ΔS, +ΔG 
D) -ΔH, -ΔS, +ΔG 
E) -ΔH, +ΔS, +ΔG 
Answer: C 
Topic: Concept 8.2
Skill: Comprehension

23)  When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows: 
A) +ΔG, +ΔH, +ΔS 
B) +ΔG, +ΔH, -ΔS 
C) +ΔG, -ΔH, -ΔS 
D) -ΔG, +ΔH, +ΔS 
E) -ΔG, -ΔH, -ΔS 
Answer: B 
Topic: Concept 8.2
Skill: Comprehension

24)  A chemical reaction that has a positive ΔG is correctly described as 
A) endergonic. 
B) endothermic. 
C) enthalpic. 
D) spontaneous. 
E) exothermic. 
Answer: A 
Topic: Concept 8.2
Skill: Knowledge

25)  Why is ATP an important molecule in metabolism? 
A) Its hydrolysis provides an input of free energy for exergonic reactions. 
B) It provides energy coupling between exergonic and endergonic reactions. 
C) Its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy. 
D) A and B only 
E) A, B and C 
Answer: B 
Topic: Concept 8.3
Skill: Comprehension

26)  The hydrolysis of ATP to ADP and inorganic phosphate (ATP + H2O → ADP + Pi ) 
A) has a ΔG of  about -7 kcal/mol under standard conditions. 
B) involves hydrolysis of a terminal phosphate bond of ATP. 
C) can occur spontaneously under appropriate conditions. 
D) Only A and B are correct. 
E) A, B, and C are correct. 
Answer: E 
Topic: Concept 8.3
Skill: Knowledge

27)  When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP.  Which of the following is the best explanation for this observation? 
A) Cells are open systems, but a test tube is a closed system. 
B) Cells are less efficient at heat production than nonliving systems. 
C) The hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube. 
D) The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes. 
E) Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat. 
Answer: E 
Topic: Concept 8.3
Skill: Application

28)  ATP generally energizes a cellular process by 
A) releasing heat upon hydrolysis. 
B) acting as a catalyst. 
C) coupling free energy released by ATP hydrolysis to free energy needed by other reactions. 
D) breaking a high-energy bond. 
E) binding directly to the substrate(s) of the enzyme. 
Answer: C 
Topic: Concept 8.3
Skill: Comprehension

29)  Which of the following reactions is most likely to be coupled to the reaction ATP + H2O →ADP + Pi (ΔG = -7.3 kcal/mol)? 
A) A + Pi  → AP (ΔG = +10 kcal/mol) 
B) B + Pi  → BP (ΔG = +8 kcal/mol) 
C) CP → C + Pi (ΔG = -4 kcal/mol) 
D) DP → D + Pi (ΔG = -10 kcal/mol) 
E) E + Pi → EP (ΔG = +5 kcal/mol) 
Answer: E 
Topic: Concept 8.3
Skill: Comprehension

30)  Which of the following is most similar in structure to ATP? 
A) an anabolic steroid 
B) a DNA helix 
C) RNA nucleotides 
D) an amino acid with three phosphate groups attached 
E) a phospholipid 
Answer: C 
Topic: Concept 8.3
Skill: Comprehension

31)  What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways? 
A) feedback regulation 
B) bioenergetics 
C) energy coupling 
D) entropy 
E) cooperativity 
Answer: C 
Topic: Concept 8.3
Skill: Knowledge

32)  Which of the following statements is true concerning catabolic pathways? 
A) They combine molecules into more energy-rich molecules. 
B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP. 
C) They are endergonic. 
D) They are spontaneous and do not need enzyme catalysis. 
E) They build up complex molecules such as protein from simpler compounds. 
Answer: B 
Topic: Concept 8.3
Skill: Comprehension

33)  Which of the following statements regarding ATP is (are) correct?	 
A) ATP serves as a main energy shuttle inside cells. 
B) ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants. 
C) The regeneration of ATP from ADP and phosphate is an endergonic reaction. 
D) A and B only 
E) A, B, and C 
Answer: E 
Topic: Concept 8.3
Skill: Knowledge

34)  Which of the following statements is (are) true about enzyme-catalyzed reactions? 
A) The reaction is faster than the same reaction in the absence of the enzyme. 
B) The free energy change of the reaction is the same as the reaction in the absence of the enzyme. 
C) The reaction always goes in the direction toward chemical equilibrium. 
D) A and B only 
E) A, B, and C 
Answer: A 
Topic: Concept 8.4
Skill: Comprehension

35)  How can one increase the rate of a chemical reaction? 
A) Increase the activation energy needed. 
B) Cool the reactants. 
C) Decrease the concentration of the reactants. 
D) Add a catalyst. 
E) Increase the entropy of the reactants. 
Answer: D 
Topic: Concept 8.4
Skill: Comprehension

36)  Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose.  The hydrolysis of sucrose by the enzyme sucrase results in 
A) bringing glucose and fructose together to form sucrose. 
B) the release of water from sucrose as the bond between glucose and fructose is broken. 
C) breaking the bond between glucose and fructose and forming new bonds from the atoms of water. 
D) production of water from the sugar as bonds are broken between the glucose monomers. 
E) utilization of water as a covalent bond is formed between glucose and fructose to form sucrase. 
Answer: C 
Topic: Concept 8.4
Skill: Application

37)  Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's 
A) entropy. 
B) activation energy. 
C) endothermic level. 
D) heat content. 
E) free-energy content. 
Answer: B 
Topic: Concept 8.4
Skill: Knowledge

38)  A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because 
A) the starch solution has less free energy than the sugar solution. 
B) the hydrolysis of starch to sugar is endergonic. 
C) the activation energy barrier for this reaction cannot be surmounted. 
D) starch cannot be hydrolyzed in the presence of so much water. 
E) starch hydrolysis is nonspontaneous. 
Answer: C 
Topic: Concept 8.4
Skill: Comprehension

39)  Which of the following statements regarding enzymes is true? 
A) Enzymes decrease the free energy change of a reaction. 
B) Enzymes increase the rate of a reaction. 
C) Enzymes change the direction of chemical reactions. 
D) Enzymes are permanently altered by the reactions they catalyze. 
E) Enzymes prevent changes in substrate concentrations. 
Answer: B 
Topic: Concept 8.4
Skill: Knowledge

40)  Which of the following is not true of enzymes? 
A) Enzyme catalysis is dependent on the pH and temperature of the reaction environment. 
B) Enzyme catalysis is dependent on the three-dimensional structure or conformation of the enzyme. 
C) Enzymes provide activation energy for the reaction they catalyze. 
D) Enzymes are composed primarily of protein, but they may bind nonprotein cofactors. 
E) Enzyme activity can be inhibited if the enzyme's allosteric site is bound with a noncompetitive inhibitor. 
Answer: C 
Topic: Concept 8.4
Skill: Knowledge

41)  An enzyme catalyzes a reaction by  
A) supplying the energy to speed up a reaction. 
B) lowering the energy of activation of a reaction. 
C) lowering the ΔG of a reaction. 
D) changing the equilibrium of a spontaneous reaction. 
E) increasing the amount of free energy of a reaction. 
Answer: B 
Topic: Concept 8.4
Skill: Knowledge

42)  Which of these statements regarding enzymes is false? 
A) Enzymes are proteins that function as catalysts. 
B) Enzymes display specificity for certain molecules with which they interact. 
C) Enzymes provide activation energy for the reactions they catalyze. 
D) The activity of enzymes can be regulated by other molecules. 
E) An enzyme may be used many times over for a specific reaction. 
Answer: C 
Topic: Concept 8.4
Skill: Knowledge

43)  During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ΔG of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ΔG for the new reaction? 
A) -40 kcal/mol 
B) -20 kcal/mol 
C) 0 kcal/mol 
D) +20 kcal/mol 
E) +40 kcal/mol 
Answer: B 
Topic: Concept 8.4
Skill: Comprehension

44)  The active site of an enzyme is the region that 
A) binds allosteric regulators of the enzyme. 
B) is involved in the catalytic reaction of the enzyme. 
C) binds the products of the catalytic reaction. 
D) is inhibited by the presence of a coenzyme or a cofactor. 
E) both A and B 
Answer: B 
Topic: Concept 8.4
Skill: Knowledge

45)  According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? 
A) The binding of the substrate depends on the shape of the active site. 
B) Some enzymes change their structure when activators bind to the enzyme. 
C) A competitive inhibitor can outcompete the substrate for the active site. 
D) The binding of the substrate changes the shape of the enzyme's active site. 
E) The active site creates a microenvironment ideal for the reaction. 
Answer: D 
Topic: Concept 8.4
Skill: Comprehension

46)  Many different things can alter enzyme activity.  Which of the following underlie all types of enzyme regulation? 
A) changes in the activation energy of the reaction 
B) changes in the active site of the enzyme 
C) changes in the free energy of the reaction 
D) A and B only 
E) A, B, and C 
Answer: D 
Topic: Concept 8.4
Skill: Application

Refer to Figure 8.1 to answer the following questions.

Figure 8.1

47)  Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher? 
A) curve 1 
B) curve 2 
C) curve 3 
D) curve 4 
E) curve 5 
Answer: C 
Topic: Concept 8.4
Skill: Knowledge

48)  Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid? 
A) curve 1 
B) curve 2 
C) curve 3 
D) curve 4 
E) curve 5 
Answer: D 
Topic: Concept 8.4
Skill: Knowledge

49)  Which curve was most likely generated from an enzyme that requires a cofactor? 
A) curve 1 
B) curve 2 
C) curve 4 
D) curve 5 
E) It is not possible to determine whether an enzyme requires a cofactor from these data. 
Answer: E 
Topic: Concept 8.4
Skill: Comprehension

50)  As temperature decreases, the rate of an enzyme-catalyzed reaction also decreases. Which of the following explain(s) why this occurs?  
A) Fewer substrates have sufficient energy to get over the activation energy barrier. 
B) Motion in the active site of the enzyme is slowed, thus slowing the catalysis of the enzyme. 
C) The motion of the substrate molecules decreases, allowing them to bind more easily to the active site. 
D) A and B only 
E) A, B, and C 
Answer: D 
Topic: Concept 8.4
Skill: Application

51)  ATP is often an allosteric inhibitor of key enzymes in catabolic pathways.  Which of the following statements is inconsistent with the role of ATP? 
A) ATP couples energy production in catabolic pathways to energy demand in anabolic pathways. 
B) When ATP levels are high in the cell, it is an indication that energy supply from catabolic reactions exceeds energy demand by anabolic reactions. 
C) The binding of ATP to allosteric sites on enzymes of the catabolic pathway decreases the production of ATP by the pathway. 
D) Increasing availability of ATP increases the energy available to drive endergonic reactions. 
E) When ATP levels are low in the cell, there is no inhibition of the catabolic pathway and ATP production is at a maximum. 
Answer: D 
Topic: Concept 8.4
Skill: Application

52)  Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? 
A) denaturization of the enzyme 
B) allosteric inhibition 
C) competitive inhibition 
D) saturation of the enzyme activity 
E) insufficient cofactors 
Answer: C 
Topic: Concept 8.4
Skill: Comprehension

53)  What is a nonprotein "helper" of an enzyme molecule called? 
A) accessory enzyme 
B) allosteric group 
C) coenzyme 
D) functional group 
E) enzyme activator 
Answer: C 
Topic: Concept 8.4
Skill: Knowledge

54)  Which of the following is true of enzymes? 
A) Enzymes may require a nonprotein cofactor or ion for catalysis to take place. 
B) Enzyme function is reduced if the three-dimensional structure or conformation of an enzyme is altered. 
C) Enzyme function is influenced by physical and chemical environmental factors such as pH and temperature. 
D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers. 
E) All of the above are true of enzymes. 
Answer: E 
Topic: Concept 8.4
Skill: Knowledge

55)  Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n) 
A) competitive inhibitor of the enzyme. 
B) noncompetitive inhibitor of the enzyme. 
C) allosteric activator of the enzyme. 
D) cofactor necessary for enzyme activity. 
E) coenzyme derived from a vitamin. 
Answer: D 
Topic: Concept 8.4
Skill: Knowledge

56)  Consider the following:  Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid. Which of the following is correct? 
A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate. 
B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. 
C) Succinate is the substrate, and fumarate is the product. 
D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor. 
E) Malonic acid is the product, and fumarate is a competitive inhibitor. 
Answer: C 
Topic: Concept 8.4
Skill: Comprehension

The following questions are based on the reaction A + B → C + D shown in Figure 8.2

Figure 8.2

57)  Which of the following terms best describes the reaction? 
A) endergonic 
B) exergonic 
C) anabolic 
D) allosteric 
E) nonspontaneous 
Answer: B 
Topic: Concept 8.4
Skill: Knowledge

58)  Which of the following represents the ΔG of the reaction? 
A) a 
B) b 
C) c 
D) d 
E) e 
Answer: D 
Topic: Concept 8.4
Skill: Knowledge

59)  Which of the following would be the same in an enzyme-catalyzed or noncatalyzed reaction? 
A) a 
B) b 
C) c 
D) d 
E) e 
Answer: D 
Topic: Concept 8.4
Skill: Comprehension

60)  Which of the following bests describes the reaction? 
A) negative ΔG, spontaneous 
B) positive ΔG, nonspontaneous 
C) positive ΔG, exergonic 
D) negative ΔG, endergonic 
E) ΔG of zero, chemical equilibrium 
Answer: A 
Topic: Concept 8.4
Skill: Comprehension

61)  Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products? 
A) a 
B) b 
C) c 
D) d 
E) e 
Answer: D 
Topic: Concept 8.4
Skill: Knowledge

62)  Which of the following represents the activation energy required for the enzyme-catalyzed reaction? 
A) a 
B) b 
C) c 
D) d 
E) e 
Answer: B 
Topic: Concept 8.4
Skill: Comprehension

63)  Which of the following represents the activation energy required for a noncatalyzed reaction? 
A) a 
B) b 
C) c 
D) d 
E) e 
Answer: C 
Topic: Concept 8.4
Skill: Knowledge

64)  Which best describes the reaction? 
A) The amount of free energy initially present in the reactants is indicated by "a." 
B) The amount of free energy present in the products is indicated by "e." 
C) The amount of free energy released as a result of the noncatalyzed reaction is indicated by "c." 
D) The amount of free energy released as a result of the catalyzed reaction is indicated by "d." 
E) The difference between "b" and "c" is the activation energy added by the presence of the enzyme. 
Answer: D 
Topic: Concept 8.4
Skill: Comprehension

65)  Assume that the reaction has a ΔG of -5.6 kcal/mol.  Which of the following would be true? 
A) The reaction could be coupled to power an endergonic reaction with a ΔG of +6.2 kcal/mol. 
B) The reaction could be coupled to power an exergonic reaction with a ΔG of +8.8 kcal/mol. 
C) The reaction would result in a decrease in entropy (S) and an increase in the total energy content (H) of the system. 
D) The reaction would result in an increase in entropy (S) and a decrease in the total energy content (H) of the system. 
E) The reaction would result in products (C + D) with a greater free-energy content than in the initial reactants (A + B).
Answer: D 
Topic: Concept 8.4
Skill: Comprehension

The next questions are based on the following information. 

A series of enzymes catalyze the reaction X → Y → Z → A.  Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.

66)  What is substance X? 
A) a coenzyme 
B) an allosteric inhibitor 
C) a substrate 
D) an intermediate 
E) the product 
Answer: C 
Topic: Concept 8.5
Skill: Comprehension

67)  Substance A functions as 
A) a coenzyme. 
B) an allosteric inhibitor. 
C) the substrate. 
D) an intermediate. 
E) a competitive inhibitor. 
Answer: B 
Topic: Concept 8.5
Skill: Comprehension

68)  The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as 
A) metabolic inhibition. 
B) feedback inhibition. 
C) allosteric inhibition. 
D) noncooperative inhibition. 
E) reversible inhibition. 
Answer: B 
Topic: Concept 8.5
Skill: Knowledge

69)  The regulation of enzyme function is an important aspect of cell metabolism. Which of the following is least likely to be a mechanism for enzyme regulation? 
A) allosteric regulation 
B) cooperativity 
C) feedback inhibition 
D) removing cofactors 
E) reversible inhibition 
Answer: D 
Topic: Concept 8.5
Skill: Comprehension

70)  Which of the following statements is true regarding enzyme cooperativity? 
A) A multi-enzyme complex contains all the enzymes of a metabolic pathway. 
B) A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway. 
C) A substrate molecule bound to an active site affects the active site of several subunits. 
D) Several substrate molecules can be catalyzed by the same enzyme. 
E) A substrate binds to an active site and inhibits cooperation between enzymes in a pathway. 
Answer: C 
Topic: Concept 8.5
Skill: Knowledge

71)  How does a non-competitive inhibitor decrease the rate of an enzyme reaction? 
A) by binding at the active site of the enzyme 
B) by changing the structure of the enzyme 
C) by changing the free energy change of the reaction 
D) by acting as a coenzyme for the reaction 
E) by decreasing the activation energy of the reaction 
Answer: B 
Topic: Concept 8.5
Skill: Knowledge

Use Figure 8.3 to answer the following questions.

Figure 8.3

72)  Which of the following statements correctly indicate(s) the role of ATP or ADP as an allosteric regulator?  Assume that the supply of energy for cellular processes is adjusted to meet cellular demand for energy. 
A) ATP is an allosteric inhibitor of catabolic pathways. 
B) ADP is an allosteric activator of catabolic pathways. 
C) ATP is an allosteric activator of anabolic pathways. 
D) A and B only 
E) A, B, and C 
Answer: E 
Topic: Concept 8.5
Skill: Application

73)  An increase in the level of cellular ATP is likely to occur under which of the following conditions? 
A) increased activity of catabolic pathways 
B) decreased activity of anabolic pathways 
C) allosteric inhibition of anabolic pathways 
D) A and B only 
E) A, B, and C 
Answer: E 
Topic: Concept 8.5
Skill: Comprehension

Media Activity Questions

74)  In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?  
A) potentiation 
B) cellular respiration 
C) digestion 
D) anabolism 
E) redox 
Answer: B 
Topic: Web/CD Activity: Energy Transformations

75)  What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?  
A) anabolism 
B) hydrolysis 
C) dehydration decomposition 
D) entropic 
E) dehydration synthesis 
Answer: B 
Topic: Web/CD Activity: The Structure of ATP

76)  In the reaction A → B + C + heat, 
A) there is a net input of energy. 
B) the potential energy of the products is greater than that of the reactant. 
C) the potential energy of the products is the same as that of the reactant. 
D) the potential energy of the products is less than that of the reactant. 
E) entropy has decreased. 
Answer: D 
Topic: Web/CD Activity: Chemical Reactions and ATP

77)  What is the fate of the phosphate group that is removed when ATP is converted to ADP?  
A) It is acquired by a reactant in an endergonic reaction. 
B) It is used to convert an ATP into an AQP. 
C) It is acquired by a reactant in a spontaneous reaction. 
D) It is acquired by a reactant in an exergonic reaction. 
E) It is broken down into one phosphorus and four oxygen atoms. 
Answer: A 
Topic: Web/CD Activity: Chemical Reactions and ATP

78)  What name is given to the reactants in an enzymatically catalyzed reaction?  
A) EA
B) products 
C) active sites 
D) reactors 
E) substrate 
Answer: E 
Topic: Web/CD Activity: How Enzymes Work

Self-Quiz Questions

79)  Choose the pair of terms that correctly completes this sentence:
Catabolism is to anabolism as ________ is to ________. 
A) exergonic; spontaneous 
B) exergonic; endergonic 
C) free energy; entropy 
D) work; energy 
E) entropy; enthalpy 
Answer: B 

80)  Most cells cannot harness heat to perform work because 
A) heat is not a form of energy. 
B) cells do not have much heat; they are relatively cool. 
C) temperature is usually uniform throughout a cell. 
D) heat can never be used to do work. 
E) heat denatures enzymes. 
Answer: C 

81)  According to the first law of thermodynamics, 
A) matter can be neither created nor destroyed. 
B) energy is conserved in all processes. 
C) all processes increase the order of the universe. 
D) systems rich in energy are intrinsically stable. 
E) the universe constantly loses energy because of friction. 
Answer: B 

82)  Which of the following metabolic processes can occur without a net influx of energy from some other process? 
A) ADP + Pi → ATP + H2O 
B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 
C) 6 CO2 + 6 H2O → C6H12O6 + 6 O2 
D) amino acids → protein 
E) glucose + fructose → sucrose 
Answer: B 

83)  If an enzyme has been inhibited noncompetitively,  
A) the △G for the reaction it catalyzes will always be negative. 
B) the active site will be occupied by the inhibitor molecule. 
C) raising substrate concentration will increase the inhibition. 
D) more energy will be necessary to initiate the reaction. 
E) the inhibitor molecule may be chemically unrelated to the substrate. 
Answer: E 

84)  If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is to 
A) add more of the enzyme. 
B) heat the solution to 90°C. 
C) add more substrate. 
D) add an allosteric inhibitor. 
E) add a noncompetitive inhibitor. 
Answer: A 

85)  If an enzyme is added to a solution where its substrates and products are in equilibrium, what would occur? 
A) Additional product would be formed. 
B) Additional substrate would be formed. 
C) The reaction would change from endergonic to exergonic. 
D) The free energy of the system would change. 
E) Nothing; the reaction would stay at equilibrium. 
Answer: E 

86)  Some bacteria are metabolically active in hot springs because 
A) they are able to maintain a cooler internal temperature. 
B) high temperatures make catalysis unnecessary. 
C) their enzymes have high optimal temperatures. 
D) their enzymes are insensitive to temperature. 
E) they use molecules other than proteins as their main catalysts. 
Answer: C 

87)  Which of the following characteristics is not associated with allosteric regulation of an enzyme's activity? 
A) A mimic of the substrate competes for the active site. 
B) A naturally occurring molecule stabilizes a catalytically active conformation. 
C) Regulatory molecules bind to a site remote from the active site. 
D) Inhibitors and activators may compete with one another. 
E) The enzyme usually has a quaternary structure. 
Answer: A 

88)  In the following branched metabolic pathway, a dotted arrow with a minus sign symbolizes inhibition of a metabolic step by an end product:

Which reaction would prevail if both Q and S were present in the cell in high concentrations? 
A) L → M 
B) M → O 
C) L → N 
D) O → P 
E) R → S 
Answer: C