1. 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
2. Which of the following is (are) true for anabolic
pathways?
A) They do not depend on enzymes.
B) They are usually highly spontaneous chemical
reactions.
C) They consume energy to build up polymers from
monomers.
D) They release energy as they degrade polymers to
monomers.
E) They consume energy to decrease the entropy of the
organism and its environment.
Answer: C
3. 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
4. For living organisms, which of the following is an
important consequence of the first law of thermodynamics?
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 grow by converting energy into organic
matter.
E) Life does not obey the first law of thermodynamics.
Answer: B
5. 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 exactly 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 cause a greater
increase in entropy in their environment than the decrease in entropy
associated with their growth.
E) Living organisms are able to transform energy into
entropy.
Answer: D
6. 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
7. 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
8. Which of the following statements is representative of
the second law of thermodynamics?
A) Conversion of energy from one form to another is
always accompanied by some gain of free energy.
B) Heat represents a form of energy that can be used by
most organisms to do work.
C) Without an input of energy, organisms would tend
toward decreasing 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: D
9. Which of the following types of reactions would
decrease the entropy within a cell?
A) anabolic reactions
B) hydrolysis
C) respiration
D) digestion
E) catabolic reactions
Answer: A
10. Biological evolution of life on Earth, from simple
prokaryote-like cells to large, multicellar eukaryotic organisms,
A) has occurred in accordance with the laws of
thermodynamics.
B) has caused an increase in the entropy of the planet.
C) has been made possible by expending Earth's energy
resources.
D) has occurred in accordance with the laws of
thermodynamics, by expending Earth's energy resources and causing an increase
in the entropy of the planet.
E) violates the laws of thermodynamics because Earth is a
closed system.
Answer: A
11. Which of the following is an example of potential
rather than kinetic energy?
A) the muscle contractions of a person mowing grass
B) water rushing over Niagara Falls
C) light flashes emitted by a firefly
D) a molecule of glucose
E) the flight of an insect foraging for food
Answer: D
12. Which of the following is the smallest closed system?
A) a cell
B) an organism
C) an ecosystem
D) Earth
E) the universe
Answer: E
13. Which of the following is true of metabolism in its
entirety in all organisms?
A) Metabolism depends on a constant supply of energy from
food.
B) Metabolism depends on an organism's adequate
hydration.
C) Metabolism uses all of an organism's resources.
D) Metabolism consists of all the energy transformation
reactions in an organism.
E) Metabolism manages the increase of entropy in an
organism.
Answer: D
14. The mathematical expression for the change in free
energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?
A) ΔS is the change in enthalpy, a measure of randomness.
B) ΔH is the change in entropy, the energy available to
do work.
C) ΔG is the change in free energy.
D) T is the temperature in degrees Celsius.
Answer: C
15. A system at chemical equilibrium
A) consumes energy at a steady rate.
B) releases energy at a steady rate.
C) consumes or releases energy, depending on whether it
is exergonic or endergonic.
D) has zero kinetic energy.
E) can do no work.
Answer: E
16. 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) The reaction goes only in a forward direction: all
reactants will be converted to products, but no products will be converted to
reactants.
D) A net input of energy from the surroundings is
required for the reactions to proceed.
E) The reactions are rapid.
Answer: B
17. 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 not being produced or used in any active metabolic pathway
E) no possibility of having chemical equilibrium in any
living cell
Answer: D
18. 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
19. 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
20. A chemical reaction that has a positive ΔG is
correctly described as
A) endergonic.
B) endothermic.
C) enthalpic.
D) spontaneous.
E) exothermic.
Answer: A
21. Which of the following best describes enthalpy (H)?
A) the total kinetic energy of a system
B) the heat content of a chemical system
C) the system's entropy
D) the cell's energy equilibrium
E) the condition of a cell that is not able to react
Answer: B
22. For the hydrolysis of ATP to ADP + Pi, the free
energy change is -7.3 kcal/mol under standard conditions (1 M concentration of
both reactants and products). In the cellular environment, however, the free
energy change is about -13 kcal/mol. What can we conclude about the free energy
change for the formation of ATP from ADP and Pi under cellular conditions?
A) It is +7.3 kcal/mol.
B) It is less than +7.3 kcal/mol.
C) It is about +13 kcal/mol.
D) It is greater than +13 kcal/mol.
E) The information given is insufficient to deduce the
free energy change.
Answer: C
23. 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) Its terminal phosphate bond has higher energy than the
other two.
E) It is one of the four building blocks for DNA
synthesis.
Answer: B
24. 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) Reactant and product concentrations in the test tube
are different from those in the cell.
Answer: E
25. Which of the following is most similar in structure
to ATP?
A) a pentose sugar
B) a DNA nucleotide
C) an RNA nucleotide
D) an amino acid with three phosphate groups attached
E) a phospholipid
Answer: C
26. Which of the following statements is true concerning
catabolic pathways?
A) They combine molecules into more energy-rich
molecules.
B) They supply energy, primarily in the form of ATP, for
the cell's work.
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
27. When chemical, transport, or mechanical work is done
by an organism, what happens to the heat generated?
A) It is used to power yet more cellular work.
B) It is used to store energy as more ATP.
C) It is used to generate ADP from nucleotide precursors.
D) It is lost to the environment.
E) It is transported to specific organs such as the
brain.
Answer: D
28. When ATP releases some energy, it also releases inorganic
phosphate. What purpose does this serve (if any) in the cell?
A) The phosphate is released as an excretory waste.
B) The phosphate can only be used to regenerate more ATP.
C) The phosphate can be added to water and excreted as a
liquid.
D) The phosphate may be incorporated into any molecule
that contains phosphate.
E) It enters the nucleus to affect gene expression.
Answer: D
29. A number of systems for pumping ions across membranes
are powered by ATP. Such ATP-powered pumps are often called ATPases although
they don't often hydrolyze ATP unless they are simultaneously transporting
ions. Because small increases in calcium ions in the cytosol can trigger a
number of different intracellular reactions, cells keep the cytosolic calcium
concentration quite low under normal conditions, using ATP-powered calcium
pumps. For example, muscle cells transport calcium from the cytosol into the
membranous system called the sarcoplasmic reticulum (SR). If a resting muscle
cell's cytosol has a free calcium ion concentration of 10⁻⁷ while the
concentration in the SR is 10⁻², then how is the ATPase acting?
A) ATPase activity must be powering an inflow of calcium
from the outside of the cell into the SR.
B) ATPase activity must be transferring Pi to the SR to
enable this to occur.
C) ATPase activity must be pumping calcium from the
cytosol to the SR against the concentration gradient.
D) ATPase activity must be opening a channel for the
calcium ions to diffuse back into the SR along the concentration gradient.
E) ATPase activity must be routing calcium ions from the
SR to the cytosol, and then to the cell's environment.
Answer: C
30. What is the difference (if any) between the structure
of ATP and the structure of the precursor of the A nucleotide in RNA?
A) The sugar molecule is different.
B) The nitrogen-containing base is different.
C) The number of phosphates is three instead of one.
D) The number of phosphates is three instead of two.
E) There is no difference.
Answer: E
31. Which of the following statements is 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 opposite
from the reaction that occurs in the absence of the enzyme.
C) The reaction always goes in the direction toward
chemical equilibrium.
D) Enzyme-catalyzed reactions require energy to activate
the enzyme.
E) Enzyme-catalyzed reactions release more free energy
than noncatalyzed reactions.
Answer: A
32. 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) equilibrium point.
E) free-energy content.
Answer: B
33. 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
34. Which of the following statements regarding enzymes
is true?
A) Enzymes increase the rate of a reaction by making the
reaction more exergonic.
B) Enzymes increase the rate of a reaction by lowering
the activation energy barrier.
C) Enzymes increase the rate of a reaction by reducing
the rate of reverse reactions.
D) Enzymes change the equilibrium point of the reactions
they catalyze.
E) Enzymes make the rate of a reaction independent of
substrate concentrations.
Answer: B
35. During a laboratory experiment, you discover that an
enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of
enzyme in the reaction, what will be the ∆G 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
36. 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 noncompetitive inhibitors of the enzyme.
D) is inhibited by the presence of a coenzyme or a
cofactor.
Answer: B
37. 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
38. Mutations that result in single amino acid substitutions
in an enzyme
A) can have no effect on the activity or properties of
the enzyme.
B) will almost always destroy the activity of the enzyme.
C) will often cause a change in the substrate specificity
of the enzyme.
D) may affect the physicochemical properties of the
enzyme such as its optimal temperature and pH.
E) may, in rare cases, cause the enzyme to run reactions
in reverse.
Answer: D
39. 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
40. Which of the following is true of enzymes?
A) Nonprotein cofactors alter the substrate specificity
of enzymes.
B) Enzyme function is increased if the 3-D structure or
conformation of an enzyme is altered.
C) Enzyme function is independent of physical and
chemical environmental factors such as pH and temperature.
D) Enzymes increase the rate of chemical reaction by
lowering activation energy barriers.
E) Enzymes increase the rate of chemical reaction by
providing activation energy to the substrate.
Answer: D
41. 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
42. In order to attach a particular amino acid to the
tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase,
is required, along with ATP. Initially, the enzyme has an active site for ATP
and another for the amino acid, but it is not able to attach the tRNA. What
must occur in order for the final attachment to occur?
A) The ATP must first have to attach to the tRNA.
B) The binding of the first two molecules must cause a
3-D change that opens another active site on the enzyme.
C) The ATP must be hydrolyzed to allow the amino acid to
bind to the synthetase.
D) The tRNA molecule must have to alter its shape in
order to be able to fit into the active site with the other two molecules.
E) The 3' end of the tRNA must have to be cleaved before
it can have an attached amino acid.
Answer: B
43. Some of the drugs used to treat HIV patients are
competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately,
the high mutation rate of HIV means that the virus rapidly acquires mutations
with amino acid changes that make them resistant to these competitive
inhibitors. Where in the reverse transcriptase enzyme would such amino acid
changes most likely occur in drug-resistant viruses?
A) in or near the active site
B) at an allosteric site
C) at a cofactor binding site
D) in regions of the protein that determine packaging
into the virus capsid
E) such mutations could occur anywhere with equal
probability
Answer: A
44. Protein kinases are enzymes that transfer the
terminal phosphate from ATP to an amino acid residue on the target protein.
Many are located on the plasma membrane as integral membrane proteins or
peripheral membrane proteins. What purpose may be served by their plasma
membrane localization?
A) ATP is more abundant near the plasma membrane.
B) They can more readily encounter and phosphorylate
other membrane proteins.
C) Membrane localization lowers the activation energy of
the phosphorylation reaction.
D) They flip back and forth across the membrane to access
target proteins on either side.
E) They require phospholipids as a cofactor.
Answer: B
45. When you have a severe fever, what grave consequence
may occur if the fever is not controlled?
A) destruction of your enzymes' primary structure
B) removal of amine groups from your proteins
C) change in the tertiary structure of your enzymes
D) removal of the amino acids in active sites of your
enzymes
E) binding of your enzymes to inappropriate substrates
Answer: C
46. How does a noncompetitive inhibitor decrease the rate
of an enzyme reaction?
A) by binding at the active site of the enzyme
B) by changing the shape of the enzyme's active site
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
47. The mechanism in which the end product of a metabolic
pathway inhibits an earlier step in the pathway is most precisely described as
A) metabolic inhibition.
B) feedback inhibition.
C) allosteric inhibition.
D) noncooperative inhibition.
E) reversible inhibition.
Answer: B
48. Which of the following statements describes enzyme
cooperativity?
A) A multienzyme 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 of one
subunit promotes substrate binding to the active site of other 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
49. Allosteric enzyme regulation is usually associated
with
A) lack of cooperativity.
B) feedback inhibition.
C) activating activity.
D) an enzyme with more than one subunit.
E) the need for cofactors.
Answer: D
50. Which of the following is an example of
cooperativity?
A) the binding of an end product of a metabolic pathway
to the first enzyme that acts in the pathway
B) one enzyme in a metabolic pathway passing its product
to act as a substrate for the next enzyme in the pathway
C) a molecule binding at one unit of a tetramer, allowing
faster binding at each of the other three
D) the effect of increasing temperature on the rate of an
enzymatic reaction
E) binding of an ATP molecule along with one of the
substrate molecules in an active site
Answer: C
51. Protein kinases are enzymes that catalyze
phosphorylation of target proteins at specific sites, whereas protein phosphatases
catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation
and dephosphorylation can function as an on-off switch for a protein's
activity, most likely through
A) the change in a protein's charge leading to a
conformational change.
B) the change in a protein's charge leading to cleavage.
C) a change in the optimal pH at which a reaction will
occur.
D) a change in the optimal temperature at which a
reaction will occur.
E) the excision of one or more peptides.
Answer: A
52. Besides turning enzymes on or off, what other means
does a cell use to control enzymatic activity?
A) cessation of cellular protein synthesis
B) localization of enzymes into specific organelles or
membranes
C) exporting enzymes out of the cell
D) connecting enzymes into large aggregates
E) hydrophobic interactions
Answer: B
53. An important group of peripheral membrane proteins
are enzymes such as the phospholipases that cleave the head groups of
phospholipids. What properties must these enzymes exhibit?
A) resistance to degradation
B) independence from cofactor interaction
C) water solubility
D) lipid solubility
E) membrane-spanning domains
Answer: C
54. In experimental tests of enzyme evolution, where a
gene encoding an enzyme is subjected to multiple cycles of random mutagenesis
and selection for altered substrate specificity, the resulting enzyme had
multiple amino acid changes associated with altered substrate specificity.
Where in the enzyme were these amino acid changes located?
A) only in the active site
B) only in the active site or near the active site
C) in or near the active site and at surface sites away
from the active site
D) only at surface sites away from the active site
E) only in the hydrophobic interior of the folded protein
Answer: C
55. How might an amino acid change at a site distant from
the active site of the enzyme alter the enzyme's substrate specificity?
A) by changing the enzyme's stability
B) by changing the enzyme's location in the cell
C) by changing the shape of the protein
D) by changing the enzyme's pH optimum
E) an amino acid change away from the active site cannot
alter the enzyme's substrate specificity
Answer: C
56.
For the enzyme-catalyzed reaction shown in the figure,
Which of these treatments will cause the greatest increase in the rate of the
reaction, if the initial reactant concentration is 1.0 micromolar?
A) doubling the activation energy needed
B) cooling the reaction by 10°C
C) doubling the concentration of the reactants to 2.0
micromolar
D) doubling the enzyme concentration
E) increasing the concentration of reactants to 10.0
micromolar, while reducing the concentration of enzyme by 1/2
Answer: D
57. In the figure, why does the reaction rate plateau at
higher reactant concentrations?
A) Feedback inhibition by product occurs at high reactant
concentrations.
B) Most enzyme molecules are occupied by substrate at
high reactant concentrations.
C) The reaction nears equilibrium at high reactant
concentrations.
D) The activation energy for the reaction increases with
reactant concentration.
E) The rate of the reverse reaction increases with
reactant concentration.
Answer: B
58. Which curve(s) on the graphs may represent the
temperature and pH profiles of an enzyme taken from a bacterium that lives in a
mildly alkaline hot springs at temperatures of 70°C or higher?
A) curves 1 and 5
B) curves 2 and 4
C) curves 2 and 5
D) curves 3 and 4
E) curves 3 and 5
Answer: E
59. Which temperature and pH profile curves on the graphs
were most likely generated from analysis of an enzyme from a human stomach
where conditions are strongly acid?
A) curves 1 and 4
B) curves 1 and 5
C) curves 2 and 4
D) curves 2 and 5
E) curves 3 and 4
Answer: A
60. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following terms best describes the forward
reaction in Figure 8.1?
A) endergonic, ∆G > 0
B) exergonic, ∆G < 0
C) endergonic, ∆G < 0
D) exergonic, ∆G > 0
E) chemical equilibrium, ∆G = 0
Answer: B
61. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the ΔG of the reaction
in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: D
62. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following in Figure 8.1 would be the same in
either an enzyme-catalyzed or a noncatalyzed reaction?
A) a
B) b
C) c
D) d
E) e
Answer: D
63. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the activation energy
needed for the enzyme-catalyzed reverse reaction, C + D → A + B, in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: A
64. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the difference between
the free-energy content of the reaction and the free-energy content of the
products in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: D
65. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the activation energy
required for the enzyme-catalyzed reaction in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: B
66. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the activation energy
required for a noncatalyzed reaction in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: C
67. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Which of the following represents the activation energy
needed for the noncatalyzed reverse reaction, C + D → A + B, in Figure 8.1?
A) a
B) b
C) c
D) d
E) e
Answer: E
68. This question is based on the reaction A + B ↔ C + D
shown in the figure.
Assume that the reaction in Figure 8.1 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
69. Which of the following is the most correct
interpretation of the figure?
A) Inorganic phosphate is created from organic phosphate.
B) Energy from catabolism can be used directly for
performing cellular work.
C) ADP + Pi are a set of molecules that store energy for
catabolism.
D) ATP is a molecule that acts as an intermediary to
store energy for cellular work.
E) Pi acts as a shuttle molecule to move energy from ATP
to ADP.
Answer: D
70. How do cells use the ATP cycle shown in the figure?
A) Cells use the cycle to recycle ADP and phosphate.
B) Cells use the cycle to recycle energy released by ATP
hydrolysis.
C) Cells use the cycle to recycle ADP, phosphate, and the
energy released by ATP hydrolysis.
D) Cells use the cycle to generate or consume water
molecules as needed.
E) Cells use the cycle primarily to generate heat.
Answer: A
71. 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.
Based on this information, 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
72. 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.
What is malonic acid's role with respect to succinate
dehydrogenase?
A) It is a competitive inhibitor.
B) It blocks the binding of fumarate.
C) It is a noncompetitive inhibitor.
D) It is able to bind to succinate.
E) It is an allosteric regulator.
Answer: A
73. 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.
What is substance X?
A) a coenzyme
B) an allosteric inhibitor
C) a substrate
D) an intermediate
E) the product
Answer: C
74. 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.
With respect to the enzyme that converts X to Y,
substance A functions as
A) a coenzyme.
B) an allosteric inhibitor.
C) the substrate.
D) an intermediate.
E) a competitive inhibitor.
Answer: B
75. 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
76. 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 must remain constant during work.
Answer: C
77. 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
78. If an enzyme in solution is saturated with substrate,
the most effective way to obtain a 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
79. Some bacteria are metabolically active in hot springs
because
A) they are able to maintain a lower internal
temperature.
B) high temperatures make catalysis unnecessary.
C) their enzymes have high optimal temperatures.
D) their enzymes are completely insensitive to
temperature.
E) they use molecules other than proteins or RNAs as
their main catalysts.
Answer: C
80. If an enzyme is added to a solution where its
substrate and product are in equilibrium, what will occur?
A) Additional product will be formed.
B) Additional substrate will be formed.
C) The reaction will change from endergonic to exergonic.
D) The free energy of the system will change.
E) Nothing; the reaction will stay at equilibrium.Answer : E
