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Sample Test
Package Title: Test Bank
Course Title: Karp6e
Chapter Number: 3
Question Type: Multiple Choice
1) The energy stored in ATP is converted to mechanical energy
that moves organelles around within the cell. This is an example of
__________.
1. a)
being exothermic
2. b)
being endothermic
3. c)
energy transduction
4. d)
polymerization
5. e)
catheterization
Answer: c
Difficulty: Medium
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
2) Entropy is associated with the _______ movement of particles
of matter, which because they are _____ cannot accomplish a directed work process.
1. a)
rapid, directed
2. b)
random, random
3. c)
rapid, random
4. d)
slow, rapid
5. e)
random, slow
Answer: b
Difficulty: Easy
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
3) Enthalpy is ________.
1. a)
the energy available to do work
2. b)
the total energy content of a system
3. c)
named after J. Willard Gibbs
4. d)
the energy available to do work and the total energy content of a system
5. e) All
of these are correct.
Answer: b
Difficulty: Easy
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
4) Given the equation DG = DH – TDS, which set of conditions
would result in a reaction that is unambiguously nonspontaneous?
1. a)
entropy decreases and the reaction is endothermic
2. b)
entropy increases and the reaction is exothermic
3. c)
entropy stays the same and there is no change in enthalpy
4. d)
entropy decreases and the reaction is exothermic
5. e)
entropy increases and the reaction is endothermic
Answer: a
Difficulty: Hard
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
5) Which reaction below might be a suitable coupled reaction for
the reaction A + B <—> C + D (DG = -8.7 kcal/mole)?
5. a) E
+ F <—> G + H (DG = -5.4 kcal/mole)
6. b) B
+ F <—> G + H (DG = -5.4 kcal/mole)
7. c) C
+ F <—> G + H (DG = +8.3 kcal/mole)
8. d) C
+ F <—> G + H (DG = +9.7 kcal/mole)
9. e) A
+ F <—> G + H (DG = +10.2 kcal/mole)
Answer: c
Difficulty: Hard
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
6) What kind of organism reaches equilibrium?
1. a)
one that is actively metabolizing
2. b)
one with a low metabolic rate
3. c) a
dead organism
4. d) a
eukaryote
5. e) a
prokaryote
Answer: c
Difficulty: Easy
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
7) Which property below is not a characteristic of enzymes?
1. a)
They are required only in large amounts.
2. b)
They can be altered reversibly during a reaction.
3. c)
They do not alter the DG of
a reaction.
4. d)
They are used over and over again.
5. e)
They do not determine whether a reaction is exergonic or endergonic.
Answer: a
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
8) Enzymes work by ___________.
1. a)
raising the activation energy of a reaction and thus speeding up the reaction.
2. b)
lowering the activation energy of a reaction and thus speeding up the reaction.
3. c)
raising the DG of a reaction and thus speeding up the reaction.
4. d)
lowering the DG of a reaction and thus speeding up the reaction.
5. e)
changing the free energy of the products and speeding up the reaction.
Answer: b
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
9) What kind of interaction is not involved in the binding of a
substrate to a normally functioning enzyme?
1. a) H
bonds
2. b) a
transient covalent bond
3. c)
ionic bonds
4. d) a
permanent covalent bond
5. e)
hydrophobic interactions
Answer: d
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
10) The presently accepted model of enzyme action was proposed
by Daniel Koshland in the 1960s and suggested that the enzyme was a flexible
structure with an active site roughly complementary to the substrate that binds
it. After its initial interaction with the substrate, the enzyme alters
its shape and thus improves the fit of the substrate in the active site)
What is the name of this model?
1. a)
The Induced Fit model
2. b)
The Flexible Sponge model
3. c)
The Lock and Key model
4. d)
The Koshland model
5. e)
The Flexible Fit model
Answer: a
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
11) Doubling the concentration of enzyme will ______ the Vmax and
_____ the KM.
1. a)
double, not alter
2. b)
not alter, double
3. c)
double, double
4. d)
not change, not alter
5. e)
halve, halve
Answer: a
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
12) What kind of inhibitor binds very tightly to an enzyme often
forming a covalent bond with an amino acid in the active site?
1. a)
irreversible
2. b)
reversible
3. c)
uncompetitive
4. d)
reversible and uncompetitive
5. e)
None of these are correct.
Answer: a
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
13) The effect of a competitive inhibitor can be reversed by
_______.
1. a)
increasing inhibitor concentration
2. b)
increasing substrate concentration
3. c)
heating the reaction mixture
4. d)
changing the pH
5. e) massaging
the enzyme
Answer: b
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
14) What is the effect of a competitive inhibitor on an
enzyme-mediated reaction?
1. a) Vmax stays
the same, KM decreases
2. b) Vmax decreases,
KM is unchanged
3. c) Vmax increases,
KM is unchanged
4. d) Vmax stays
the same, KM is unchanged
5. e) Vmax stays
the same, KM increases
Answer: e
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
15) Proteins are dynamic molecules that are capable of ________
motion that can have important functional relevance. The existence of
this type of motion has suggested that enzymes are capable – even in the
absence of substrate – of many of the same movements that can be detected
during their catalytic cycle.
1. a)
extrinsic
2. b)
intrinsic
3. c)
instant
4. d)
built-in
5. e)
intrinsic and built-in
Answer: e
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
16) Metabolic pathways that make available raw materials from
which other molecules can be synthesized and that provide chemical energy
required for many cell activities are known as ______.
1. a)
anabolism
2. b)
catabolism
3. c)
manabolism
4. d)
allosterism
5. e)
anabolism and catabolism
Answer: b
Difficulty: Easy
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical
reactions.
Section Reference: Section 3.3 Metabolism
17) A reaction involving the gain of one or more electrons is
a(n) _________ reaction.
1. a)
oxidation
2. b)
reduction
3. c)
inclusion
4. d)
elimination
5. e)
None of these are correct.
Answer: b
Difficulty: Easy
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical
reactions.
Section Reference: Section 3.3 Metabolism
18) Glycolysis occurs in the ________; the Krebs (TCA) cycle
occurs in the ______ of eukaryotes and the ______ of prokaryotes.
1. a)
cytoplasm, cytoplasm, cytoplasm
2. b)
mitochondria, cytoplasm, mitochondria
3. c)
cytoplasm, mitochondria, cytoplasm
4. d)
cytoplasm, photosynthesis, cytoplasm
5. e)
cytoplasm, mitochondria, mitochondria
Answer: c
Difficulty: Medium
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical
reactions.
Section Reference: Section 3.3 Metabolism
19) What kind of enzyme adds phosphate groups to enzymes for the
purpose of activating or deactivating them?
1. a)
phosphatases
2. b) protein
kinases
3. c)
flippases
4. d)
glycosyltransferases
5. e)
carboxypeptidase
Answer: b
Difficulty: Easy
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical
reactions.
Section Reference: Section 3.3 Metabolism
Question Type: Essay
20) You are observing a reaction and discover that the reaction
vessel is warm to the touch. The reaction also results in an increase in
entropy. Is the reaction spontaneous? How do you know?
Answer:
Difficulty: Medium
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
Solution: The reaction is exothermic (-DH) as demonstrated by
the warm reaction vessel and entropy is increased (DS). When these values
are plugged into the equation DG = DH – TDS, the only possible result is that
DG is negative. The reaction has a negative DG and is, therefore,
spontaneous.
21) If a reaction vessel is cold to the touch and the reaction
results in an increase in order in the reaction vessel, is the reaction
spontaneous or nonspontaneous? Explain your answer.
Answer:
Difficulty: Medium
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
Solution: The reaction is nonspontaneous. The DH is
positive and the DS negative. When these values are plugged into the
equation, DG = DH – TDS, the result is a positive DG and, therefore, a
nonspontaneous reaction.
22) Do the equations below represent coupled reactions? If
not, why not?
A + B <-> C + D (DG = -5.4 kcal/mole)
E + F <-> G + H (DG = +4.4 kcal/mole)
Answer: The equations above do not represent coupled reactions
because there is no common intermediate.
Difficulty: Hard
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
23) Do the equations below represent coupled reactions? If
not, why not?
A + B <-> C + D (DG = +5.4 kcal/mole)
D + F <-> G + H (DG = -4.4 kcal/mole)
Answer:
Difficulty: Hard
Learning Objective: LO 3.1 Elaborate on the laws of thermodynamics
and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
Solution: The equations above do not represent coupled reactions
because the overall DG is not negative.
24) In the reaction A + B <—> C + D, how might the
reaction take place in the cell if the DG is very positive? How might the
reaction occur if the DG is slightly positive?
Answer:
Difficulty: Hard
Learning Objective: LO 3.1 Elaborate on the laws of
thermodynamics and their importance to biological systems.
Section Reference: Section 3.1 Bioenergetics
Solution: If DG is very positive, the reaction would probably
take place by coupling it to a reaction with a larger -DG so that when the DG
values are added up the sum is negative. If the reaction is slightly
positive, it may be coupled as well, although it may also be driven forward by
increasing the amounts of the reactants and/or decreasing the amounts of
products. The Law of Mass Action would be likely to allow the reaction to
run under these conditions.
25) You are observing an enzyme driven reaction. To the
reaction mixture you add a chemical X which inhibits the reaction. If you
add more substrate, the reaction rate approaches the Vmax of
the uninhibited reaction. Furthermore, the structure of X is similar to
the natural substrate. What kind of inhibitor is X?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: X is a competitive inhibitor. First, competitive
inhibitors resemble the substrates of the reactions they inhibit. Second,
their effects can be reversed by increasing substrate concentration, since both
the substrate and the competitive inhibitor are capable of binding to the
enzyme active site. As the amount of substrate increases relative to the
competitive inhibitor, the active site is more likely to pick up substrate and
thus reaction rate increases and the inhibition is reversed.
26) If ATP is present in relatively high amounts, what is likely
to happen to the rate of glycolytic activity in that cell?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The glycolytic pathway will probably slow down.
ATP will act like a noncompetitive inhibitor and will inhibit one of the early
reactions in the glycolytic pathway.
27) An enzyme has a KM of
20 µM and a Vmax of 50 mmoles of product/minute/µg of enzyme. After
exposure to an inhibitor and analysis on a Lineweaver – Burk plot the following
values are obtained: -1/ KM =
– 0.05 liters/µmole and 1/ Vmax =
0.04 (mmoles of product/minute/µg of enzyme)-1. What kind of inhibitor
was used in the experiment?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Since the KM has
remained the same and the Vmax has decreased,
the inhibitor was noncompetitive.
28) Why are alcoholic beverages often made in airtight
containers?
Answer:
Difficulty: Easy
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical
reactions.
Section Reference: Section 3.3 Metabolism
Solution: The alcohol in these beverages is produced by
fermentation, which only occurs in the absence of oxygen.
29) Below is a segment of a cell’s collection of biochemical
pathways. M is a product of one series of these reactions. It is
also a regulatory molecule. Look at the pathway below and indicate the
position(s) at which M is most likely to act as a feedback inhibitor when its
concentration gets too high.
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: M will be most likely to act as a feedback inhibitor
at position 1, 2 or maybe 3. Usually, a feedback inhibitor will work on
an enzyme near the beginning of the pathway that leads to its production.
Therefore, positions 1 and 2 are the most likely with 1 being slightly favored.
30) You are studying metabolic pathways and discover that two
pathways intersect so that the enzyme basinase participates in both of the
intersecting pathways, in one case using substrate K and in the other using
substrate M. When presented with substrate K in amounts significantly
larger than M, basinase converts K to L which leads eventually to the
production of the end product R. The activity of the second pathway is
depressed simultaneously. In the presence of large amounts of substrate M
and lower amounts of substrate K, the second pathway is activated and
culminates in the production of that pathway’s end product Y. The
activity of the first pathway is depressed simultaneously. What are the
alternative substrates K and M acting like?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: K and M are acting like competitive inhibitors.
If one is present in excess, the pathway involving the other is inhibited.
31) 4 ATPs per glucose molecule are made during
glycolysis. Why then is there a net production of only 2 ATPs for each
glucose molecule in the pathway?
Answer:
Difficulty: Easy
Learning Objective: LO 3.3 Discuss the main differences between
catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions.
Section Reference: Section 3.3 Metabolism
Solution: Two ATPs are used up early in glycolysis before the 4
ATPs are produced. Consequently, there is a net gain of only 2 ATPs per
glucose.
32) Why has the pharmaceutical industry drastically cut
resources devoted to the development of new antibiotics?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The decrease in the pharmaceutical industry’s
resources devoted to the development of new antibiotics is generally attributed
to three factors. First, there is a lack of financial incentives since
antibiotics are taken for only a short period of time, as opposed to drugs
prescribed for chronic conditions (diabetes, depression). Second, new
antibiotics run the risk of having a relatively short lifetime in the
marketplace as bacteria become resistant to each successive product.
Last, the most effective antibiotics are being held back from widespread use
and being kept instead as weapons of last resort when other drugs have failed.
33) A number of antibiotics attack prokaryotic protein synthesis,
but not eukaryotic protein synthesis. Name two common antibiotics that
work this way. What is their site of action and why don’t they
affect eukaryotic protein synthesis?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The antibiotics are streptomycin and the
tetracyclines. They act by binding to prokaryotic ribosomes.
Eukaryotic ribosomes are sufficiently different from those in prokaryotes to
prevent binding of these substances. Thus, eukaryotic protein synthesis
is unaffected.
34) Penicillin is an irreversible inhibitor of the transpeptidases,
enzymes that cross-link components of the bacterial cell wall. The cell
wall is thus fragile and the bacteria die. Penicillin and its derivatives
are structural analogs of the natural substrates of these enzymes. Why doesn’t
penicillin normally kill humans, unless a severe allergic reaction
(anaphylaxis) develops? How does penicillin inhibit transpeptidase?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Humans don’t have cell walls and
transpeptidases. Thus, penicillin cannot inhibit an enzyme that humans do
not possess and it will not normally harm humans. Since penicillin
occupies the transpeptidase active site, it acts somewhat like a competitive
inhibitor, but since it binds irreversibly, it is not truly competitive.
35) If an antibiotic were found to bind to a site on an essential
bacterial enzyme other than the active site, what would its most likely mode of
action be?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: It would probably be a noncompetitive inhibitor of the
affected enzyme.
36) You isolate the enzyme that synthesizes folic acid in
bacteria and conduct some enzyme kinetics experiments. You find, not
surprisingly, that sulfa drugs inhibit the enzyme’s activity. What
happens to the Vmax and KM of this enzyme when it is treated with sulfa
drugs? Why do sulfa drugs have no effect on human metabolism?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Since the sulfa drugs are competitive inhibitors, the
Vmax should stay the same and the KM should
increase. Sulfa drugs work by acting as a competitive inhibitor of an
enzyme that converts p-aminobenzoic acid (PABA) to the essential coenzyme folic
acid. Since humans lack a folic-acid synthesizing enzyme, they must
obtain this essential coenzyme in their diet and, consequently, sulfa drugs
have no effect on human metabolism.
37) What is unusual about the mechanism by which vancomycin
inhibits transpeptidation of the bacterial cell wall? Why is
it more difficult for bacteria to develop resistance to vancomycin than to
other antibiotics?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Vancomycin binds to the peptide substrate of the
transpeptidase, rather than to the enzyme itself. Normally, the
transpeptidase substrate terminates in a D-alanine—D-alanine dipeptide.
To become resistant to vancomycin, a bacterial cell must synthesize an
alternate terminus that does not bind the drug. This is a roundabout
process that requires the acquisition of several new enzymatic
activities. Consequently, vancomycin is the antibiotic to which bacteria
have been least able to develop resistance and thus is usually given as a last
resort when other antibiotics have failed.
38) Where is S. aureus usually found in humans? What
kind of hospitalized patients develop life-threatening S. aureus
infections? Distressingly, instead of just showing up in hospitals,
methicillin-resistant S. aureus (MRSA) is showing up in other places.
What are some examples?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The skin and nasal passages. Those patients who have
open wounds or invasive tubes. It has appeared in community
settings, like high school gyms and children’s daycare centers.
39) What is the reason for treating a patient simultaneously
with two antibiotics against the same bacterium?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The hope is that while a bacterium may have the gene
for resistance to one antibiotic, it will not have a gene conferring resistance
to the second antibiotic) Also, in the case of penicillin, treatment with
penicillin and an agent that inhibits b-lactamase may protect penicillin
against b-lactamase and allow it to work.
40) The development of bacterial resistance to antibiotics is an
example of what engine of evolution?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Natural selection.
41) Which antibiotic inhibits the enzyme DNA gyrase, which is
required for bacterial DNA replication?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Quinolones
42) Penicillin fits into the active site of transpeptidases and
thus acts as what kind of inhibitor? How is the effect of such an inhibitor
usually able to be reversed? Why would this approach not work
with penicillin?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Penicillin acts as a competitive inhibitor since it
occupies the active site. Such inhibition is usually reversible by
increasing substrate concentration, which would tend to displace the inhibitor
from the active site. An increase in substrate concentration does not
reverse penicillin’s effect because penicillin forges a covalent bond between
itself and the enzyme active site, thus occupying the active site permanently
and irreversibly inactivating the enzyme.
43) What are some ways that antibiotic resistance genes can be
passed from bacterium to bacterium?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: DNA can pass from bacterium to bacterium through
conjugation in which bacteria pass DNA through tubelike connections joining two
of them together. Bacteria may also exchange genes by the process of
transduction in which a virus carries bacterial DNA from one bacterium to
another. DNA may also be passed by transformation in which a bacterium
can pick up naked DNA from its surrounding medium.
44) How does the AIDS virus manage to avoid the effects of drugs
that attack its enzymes so effectively?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The replicating enzyme of HIV is reverse
transcriptase. This enzyme has a much higher error rate than DNA
polymerase (~1 mistake for every 10,000 bases duplicated) and makes a large
number of mistakes leading to a higher mutation rate. When combined with
the high rate of virus production (>108 virus particles produced in a person
per day), the likelihood of producing drug-resistant variants in a single
infected individual is relatively high.
45) Many bacteria have acquired resistance to penicillin by
picking up the gene for b-lactamase.
However, some have developed resistance without acquiring this gene. How
do these bacteria escape the fatal effects of penicillin?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Some are resistant because they possess modifications
in their cell walls that block the entry of the antibiotic. Others are
resistant because they are able to selectively export the antibiotic once it
has entered the cell. Still others are resistant because they possess
modified transpeptidases that fail to bind the antibiotic as a result of
mutations in the gene that encodes the enzyme.
46) What strategies are employed to combat the ability of the
AIDS (HIV) virus to develop drug-resistant variants?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: One strategy employed is having patients take several
drugs at once (cocktails), each of which is targeted at different viral
enzymes. This strategy greatly reduces the likelihood that a variant will
emerge that is resistant to all of the drugs. Second, drugs have been
designed that interact with the most highly conserved portions of each targeted
enzyme, those portions within which mutations are most likely to produce a defective
enzyme.
47) There have been two new classes of antibiotics developed and
approved since 1963. One of these antibiotics acts specifically on
bacterial ribosomes. What is it? Another new group of antibiotics
is the cyclic lipopeptides. What is a representative of this group and
how does this group of antibiotics work?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: The antibiotic linezolid (brand name Zyvox) acts
specifically on bacterial ribosomes and interferes with protein synthesis; it
was introduced in 2000. A representative cyclic lipopeptide is
daptomycin (brand name Cubicin). They disrupt bacterial membrane
function.
48) Certain bacteria have an adaptation that allows them to
render penicillin harmless; they have adapted due to their possession of an
enzyme called penicillinase. How does it render them immune to the
effects of penicillin?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Another name for penicillinase is b-lactamase.
This enzyme can open the b-lactam ring. Penicillin is a b-lactam because
it contains the four-membered b-lactam ring. Thus, penicillinase breaks
the ring and renders penicillin harmless to the bacterium.
49) Why was methicillin developed?
Answer:
Difficulty: Medium
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: Methicillin is a penicillin derivative that is more
resistant to hydrolysis by penicillinase) Unfortunately, natural
selection leads rapidly to the evolution of bacteria whose b-lactamase can
split the new forms of the antibiotic.
50) How are new compounds typically screened for their
effectiveness as antibiotics?
Answer:
Difficulty: Easy
Learning Objective: LO 3.2 Explain how enzymes can be specific
towards the substrate they bind and why this may lower the activation energy of
a reaction.
Section Reference: Section 3.2 Enzymes as Biological Catalysts
Solution: A compound is tested for its ability to kill bacterial
cells that are growing in a culture dish or a laboratory animal.
Alternatively, it is tested for its ability to bind and inhibit a particular
target protein that has been purified from bacterial cells.
Package Title: Test Bank
Course Title: Karp7e
Chapter Number: 4
Question Type: Multiple Choice
1) Which of the following is a function of membranes?
1. a)
compartmentalization
2. b)
selectively permeable barrier
3. c)
mediates intercellular interactions
4. d)
helps cells respond to external stimuli
5. e)
All of these are correct.
Answer: e
Difficulty: Easy
Learning Objective: LO 4.1 Discuss the functions of biological
membranes.
Section Reference: Section 4.1 An Overview of Membrane Functions
2) Which of the following is not a function of membranes?
1. a) transporting
solutes
2. b)
scaffold for biochemical activities
3. c)
energy transduction
4. d)
signal transition
5. e)
signal transduction
Answer: d
Difficulty: Easy
Learning Objective: LO 4.1 Discuss the functions of biological
membranes.
Section Reference: Section 4.1 An Overview of Membrane Functions
3) What evidence convinced Overton that membranes were composed
of lipids?
1. a) He
could see the lipids in the microscope.
2. b)
Membranes were destroyed by enzymes that degraded lipids.
3. c) He
found that more lipid-soluble solutes enter root hair cells faster than polar
solutes.
4. d)
Membranes dissolved in gasoline.
5. e)
Membranes did not dissolve in water.
Answer: c
Difficulty: Medium
Learning Objective: LO 4.2 Describe the important roles of the
membrane during the life cycle of a eukaryotic cell.
Section Reference: Section 4.2 A Brief History of Studies on
Plasma Membrane Structure
4) Gorter and Grendel extracted lipids from human red blood
cells. They calculated the total surface area for these red blood cells and
found it to be 36 µ2. How much surface area would these lipids cover once they
were spread across the surface of water?
1. a) 72
µ2
2. b) 36
µ2
3. c) 18
µ2
4. d)
144 µ2
5. e) 30
µ2
Answer: a
Difficulty: Medium
Learning Objective: LO 4.2 Describe the important roles of the
membrane during the life cycle of a eukaryotic cell.
Section Reference: Section 4.2 A Brief History of Studies on
Plasma Membrane Structure
5) What did Davson and Danielli add to their model of enzyme
structure to explain the passage of polar solutes and ions through the membrane
and to account for their selective permeability?
1. a)
They proposed protein-lined pores.
2. b)
They proposed lipid-lined pores.
3. c)
They proposed carbohydrate-lined pores.
4. d)
They proposed a protein coating on the cytoplasmic surface of the membrane.
5. e)
They proposed a carbohydrate coating on the external surface of the membrane.
Answer: a
Difficulty: Easy
Learning Objective: LO 4.2 Describe the important roles of the
membrane during the life cycle of a eukaryotic cell.
Section Reference: Section 4.2 A Brief History of Studies on
Plasma Membrane Structure
6) What are the building blocks of a phosphoglyceride,
specifically phosphatidic acid?
1. a)
glycerol + 2 phosphate groups + 1 fatty acid
2. b) glycerol
+ 1 phosphate group + 2 fatty acids
3. c)
glycerol + 1 phosphate group
4. d)
glycerol + 3 fatty acids
5. e)
glycerol + 1 phosphate group + 3 fatty acids
Answer: b
Difficulty: Easy
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
7) What word describes a molecule that contains both hydrophilic
and hydrophobic portions?
1. a)
amphoteric
2. b)
ambidextrous
3. c)
amphipathic
4. d) rings
5. e)
straight
Answer: c
Difficulty: Easy
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
8) Glycolipids have been shown to play roles in certain disease
states in humans and other mammals. Which of the situations below illustrate
the ways in which this can happen?
1. a)
failure to add a sugar to the glycolipid.
2. b)
inhibition of glycolipid synthesis.
3. c)
they are the site at which bacterial toxins like those that cause botulism and
cholera first bind cells.
4. d)
they are the site at which the influenza virus first binds a cell.
5. e)
All of these are correct.
Answer: e
Difficulty: Medium
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
9) Why did liposomes not work against diseases as hoped when
they were first tried?
1. a)
They were degraded in the bloodstream.
2. b)
Immune system phagocytes removed them from the bloodstream before they could
exert an effect.
3. c)
They leaked before getting to their target.
4. d)
They were targeted incorrectly.
5. e)
They expanded osmotically and lysed before reaching their target.
Answer: b
Difficulty: Medium
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
10) How are the new “stealth liposomes” protected from immune
system phagocytes?
1. a)
They are kept cold before use.
2. b)
They are coated with carbohydrates.
3. c)
They are given a synthetic polymer coating that protects them from immune
destruction.
4. d)
They are loaded with radioactive isotopes.
5. e)
They are colored red.
Answer: c
Difficulty: Easy
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
11) People who have the AB blood type possess ________.
1) an enzyme that adds an N-acetylgalactosamine to the end of
the oligosaccharide chain on RBC membrane glycolipids
2) an enzyme that adds a galactose to the end of the
oligosaccharide chain on RBC membrane glycolipids
3) an enzyme that adds phospholipids to the end of the
oligosaccharide chain on RBC membrane glycolipids
4) no enzymes capable of attaching galactose or
N-acetylgalactosamine to the end of the oligosaccharide chain on RBC membrane
glycolipids
1. a) 1
2. b) 2
3. c) 3
4. d) 4
5. e) 1
and 2
Answer: e
Difficulty: Medium
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
12) People who have the A blood type possess ________.
1) an enzyme that adds an N-acetylgalactosamine to the end of
the oligosaccharide chain on RBC membrane glycolipids
2) an enzyme that adds a galactose to the end of the
oligosaccharide chain on RBC membrane glycolipids
3) an enzyme that adds phospholipids to the end of the
oligosaccharide chain on RBC membrane glycolipids
4) no enzymes capable of attaching galactose or
N-acetylgalactosamine to the end of the oligosaccharide chain on RBC membrane
glycolipids
1. a) 1
2. b) 2
3. c) 3
4. d) 4
5. e) 1
and 2
Answer: a
Difficulty: Medium
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
13) People who have the O blood type possess ________.
1) an enzyme that adds an N-acetylgalactosamine to the end of
the oligosaccharide chain on RBC membrane glycolipids
2) an enzyme that adds a galactose to the end of the
oligosaccharide chain on RBC membrane glycolipids
3) an enzyme that adds phospholipids to the end of the
oligosaccharide chain on RBC membrane glycolipids
4) no enzymes capable of attaching galactose or N-acetylgalactosamine
to the end of the oligosaccharide chain on RBC membrane glycolipids
1. a) 1
2. b) 2
3. c) 3
4. d) 4
5. e) 1
and 2
Answer: d
Difficulty: Medium
Learning Objective: LO 4.3 Describe the basic structure of the
major types of lipids found in cellular membranes.
Section Reference: Section 4.3 The Chemical Composition of
Membranes
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