Campbell Biology in Focus, 2e (Urry)
Chapter 6 An Introduction to Metabolism
6.1 Multiple-Choice Questions
1) The cellular process of breaking down large molecules into smaller ones is defined as
A) catalysis.
B) metabolism.
C) anabolism.
D) dehydration.
E) catabolism.
2) The cellular process of synthesizing large molecules from smaller ones is defined as
A) catalysis.
B) metabolism.
C) anabolism.
D) dehydration.
E) catabolism.
3) Which of the following is true for anabolic pathways?
A) They do not depend on enzymes.
B) They are usually spontaneous chemical reactions.
C) They consume energy to build polymers from monomers.
D) They release energy as they degrade polymers to monomers.
4) 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) Energy cannot be transferred or transformed.
5) 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.
6) 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) Living organisms do not follow the laws of thermodynamics.
C) As a consequence of growing, organisms cause a greater increase in entropy in their
environment than the decrease in entropy associated with their growth.
D) Living organisms are able to transform energy into entropy.
7) Energy transformations are always associated with 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.
8) 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.
9) 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.
10) Which of the following types of reactions would decrease the entropy within a cell?
A) anabolic reactions
B) hydrolysis
C) diffusion
D) digestion
E) catabolic reactions
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
12) 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 manages the increase of entropy in an organism.
C) Metabolism specifically refers to the biochemical pathways involved in synthesis of
macromolecules.
D) Metabolism consists of all the energy transformation reactions in an organism.
13) Which of the following tend(s) to release energy?
A) endergonic reactions
B) dehydration reactions
C) hydrolysis reactions
D) formation of water from hydrogen and hydroxyl ions
14) A system at chemical equilibrium
A) consumes energy at a steady rate.
B) releases energy at a steady rate.
C) consumes or releases energy at a steady rate, depending on whether it is exergonic or
endergonic.
D) can do no work.
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15) 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 reaction to proceed.
16) A chemical reaction that has a positive ΔG is best described as
A) endergonic.
B) entropic
C) spontaneous.
D) exergonic.
17) Which of the following reactions tend to require an input of energy?
A) exergonic
B) dehydration
C) hydrolysis
D) catabolic
18) For the hydrolysis of ATP to ADP + ℗i, 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 ℗i 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 about +26 kcal/mol.
19) Which of the following describes the critical role that ATP plays in cellular metabolism?
A) The terminal phosphate group of ATP is attached by a particularly strong covalent bond that
releases extra energy when broken.
B) It is one of the four building blocks for RNA synthesis.
C) Hydrolysis of ATP provides energy to drive exergonic reactions in the cell.
D) ATP serves as an energy shuttle in the cell, coupling exergonic and endergonic reactions.
20) ATP hydrolysis in a test tube releases only about half as much energy as ATP hydrolysis in
the cell. Which of the following is the best explanation for this observation?
A) Cells maintain higher internal pressure, which speeds up the reaction rate.
B) ATP hydrolysis in a test tube occurs under standard conditions; in the cell, reactant and
product concentrations differ from standard conditions.
C) ATP hydrolysis in a cell produces different products than ATP hydrolysis in a test tube.
D) ATP hydrolysis in cells is catalyzed by enzymes, which releases more energy than the
uncatalyzed reaction in a test tube.
21) ATP is an example of which of the following?
A) a pentose sugar
B) a DNA nucleotide
C) an RNA nucleotide
D) an amino acid with three phosphate groups attached
22) Which of the following is an exergonic reaction?
A) synthesis of ATP from ADP and ℗i
B) a dehydration reaction between two monosaccharides to produce a disaccharide
C) formation of a peptide bond
D) hydrolysis of glycogen to release glucose monomers
23) Which of the following statements concerning catabolic pathways is true?
A) They combine molecules into larger, more energy-rich molecules.
B) They provide energy that can be used to drive cellular work.
C) They are endergonic.
D) They build up complex molecules such as protein from simpler compounds.
24) A catabolic pathway may be which of the following?
A) a set of reactions that combine monomers into larger, more energy-rich polymers
B) a set of coupled reactions that are endergonic
C) a set of reactions that form covalent bonds between molecules to store free energy
D) a set of reactions that release energy that can be used to drive cellular work
25) 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 in the form of ATP.
C) It is used to synthesize ADP.
D) It is released to the environment.
26) Hydrolysis of ATP releases energy, which results in the production of ADP and inorganic
phosphate. What is commonly the immediate fate of the inorganic phosphate in the cell?
A) It is secreted as waste.
B) It is phosphorylated.
C) It is hydrolyzed to release additional energy.
D) It is used to form a phosphorylated intermediate.
27) Hydrolysis of ATP releases energy, which results in the production of ADP and inorganic
phosphate. What is commonly the ultimate fate of inorganic phosphate produced in the cytosol?
A) It is secreted as waste.
B) It is combined with ADP to regenerate ATP.
C) It is phosphorylated.
D) It is hydrolyzed to release additional energy.
28) 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 which of the following is
the most likely mechanism by which the muscle cell ATPase maintains intracellular calcium
concentrations?
A) The ATPase pumps calcium from the outside of the cell into the SR against the concentration
gradient.
B) The ATPase pumps calcium from the cytosol into the SR against the concentration gradient.
C) The ATPase transfers ℗i to calcium ions so that they may diffuse into the SR.
D) The ATPase opens a calcium ion channel that allows calcium ions to diffuse back into the SR
along the concentration gradient.
29) 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.
30) Which of the following statements about enzyme-catalyzed reactions is true?
A) The free-energy change of the reaction is greater than when the same reaction occurs in the
absence of an enzyme.
B) The rate of the reaction is greater than when the same reaction occurs in the absence of an
enzyme.
C) Enzymes always drive reactions toward chemical equilibrium.
D) Energy from ATP is required to activate the enzyme before it can catalyze the reaction.
31) In most exergonic reactions, the reactants capable of interacting to form products typically
must first overcome a thermodynamic barrier known as the
A) entropy of the reaction.
B) energy conservation of the reaction.
C) chemical equilibrium of the reaction.
D) activation energy of the reaction.
32) 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 easily be surmounted at room
temperature.
D) starch cannot be hydrolyzed in the presence of so much water.
E) starch hydrolysis is nonspontaneous.
33) 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.
34) The ∆G for a particular enzyme-catalyzed reaction is -20 kcal/mol. If the amount of enzyme
in the reaction is doubled, 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
35) The ∆G for a particular enzyme-catalyzed reaction is -20 kcal/mol. If the enzyme is
removed, what will be the ∆G for the noncatalyzed reaction?
A) -40 kcal/mol
B) -20 kcal/mol
C) 0 kcal/mol
D) +20 kcal/mol
E) +40 kcal/mol
36) The active site of an enzyme is the region that
A) binds allosteric regulators of the enzyme.
B) binds substrates for the enzyme.
C) binds noncompetitive inhibitors of the enzyme.
D) is inhibited by the presence of a coenzyme or a cofactor.
37) The induced fit model of enzyme activity suggests which of the following?
A) The binding of substrate depends on the conformation of the active site.
B) The binding of an activator alter the conformation of the active site to bind products more
tightly.
C) The binding of substrate changes the conformation of the active site to bind substrate more
tightly.
D) The binding of a competitive inhibitor changes the shape of the active site to bind substrate
less tightly.
38) A mutation that results in a single amino acid substitution in a region of the enzyme outside
of the active site
A) may alter the ability of a competitive inhibitor to bind to the enzyme.
B) will almost always destroy the activity of the enzyme.
C) will often change the substrate specificity of the enzyme.
D) may alter the optimal pH for the enzyme.
39) A mutation that results in a single amino acid substitution in the active site of an enzyme
A) may alter the ability of a noncompetitive inhibitor to bind to the enzyme.
B) may alter the ability of an allosteric regulator to alter enzyme activity.
C) may change the substrate specificity of the enzyme.
D) may alter the ∆G for the reaction catalyzed by the enzyme.
40) Increasing the substrate concentration in an enzymatic reaction could overcome which of the
following?
A) denaturation of the enzyme
B) allosteric inhibition
C) competitive inhibition
D) saturation of the enzyme activity
41) Increasing the enzyme concentration in an enzymatic reaction could overcome which of the
following?
A) denaturation of the enzyme
B) allosteric inhibition
C) competitive inhibition
D) saturation of the enzyme activity
42) 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.
43) Under a particular set of conditions in the lab, the enzyme in a chemical reaction is saturated.
Which of the following alterations to the reaction will increase the rate at which substrate is
converted to product?
A) increasing the concentration of substrate in the reaction
B) increasing the amount of enzyme in the reaction
C) increasing the volume of the reaction without increasing the amount of substrate or enzyme
D) decreasing the concentration of product in the reaction
44) 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.
45) An aminoacyl-tRNA synthetase is the enzyme that catalyzes the attachment of a particular
amino acid to its corresponding tRNA. This reaction requires energy from ATP. The enzyme
initially binds the amino acid and ATP, but it is unable to bind the tRNA. Which of the following
would be a likely mechanism by which the enzyme ultimately binds the tRNA and attaches the
amino acid?
A) Transfer of the ATP to the tRNA opens the active site to allow the tRNA to bind.
B) Hydrolysis of ATP activates the amino acid, which is released, opening up the active site to
allow binding of the tRNA.
C) Hydrolysis of ATP phosphorylates the amino acid and results in a conformational change in
the active site, which allows the tRNA to bind.
D) Alteration in the conformation of the tRNA allows it to bind to the active site along with the
amino acid and ATP.
46) 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 enzyme that determine packaging into the virus capsid
47) A severe fever can result in death if not brought under control because
A) it may destroy the primary structure of cellular enzymes.
B) it may alter the tertiary structure of cellular enzymes.
C) it may increase the rate of cellular chemical reactions.
D) it may result in binding inappropriate substrates by cellular enzymes.