PORTAGE LEARNING CHEM 210 MODULE 8 PROBLEM
SET QUESTIONS WITH ANSWERS AND EXPLANATIONS
Question 1.
A learner wants an example of N-acetylglutamate. Which choice is best?
A. CPS I activity falling when its required activator is absent.
B. Protons accumulating outside the mitochondrial matrix during electron transport.
C. NADH oxidation coupled to proton translocation at the first ETC entry complex.
D. Severe hyperammonemia producing neurologic dysfunction.
Correct Answer: A. CPS I activity falling when its required activator is absent.
Explanation: For this module, remember that CPS I activity falling when its required
activator is absent. is a representative example of N-acetylglutamate. N-acetylglutamate
is an essential allosteric activator of mitochondrial carbamoyl phosphate synthetase I. The
other options were drawn from related module concepts, but each illustrates a different
biochemical feature. Matching the defining feature to the example is the most reliable way
to solve this type of problem.
Question 2.
A student is reviewing key terms. Which statement correctly characterizes
argininosuccinate lyase?
A. Nitrogen disposal pathways safely remove excess amino nitrogen, largely by converting
toxic ammonia into urea for excretion.
B. Argininosuccinate lyase cleaves argininosuccinate to arginine and fumarate.
C. Complexes I, III, and IV use electron-transfer energy to move protons from the matrix to
the intermembrane space; Complex II does not.
D. Complex IV transfers electrons from cytochrome c to oxygen, forms water, and
contributes to proton translocation.
Correct Answer: B. Argininosuccinate lyase cleaves argininosuccinate to
arginine and fumarate.
Explanation: This choice is correct because Argininosuccinate lyase cleaves
argininosuccinate to arginine and fumarate. That definition directly matches the term
named in the stem. By contrast, Complex IV refers to a different idea: Complex IV transfers
electrons from cytochrome c to oxygen, forms water, and contributes to proton
translocation. Keeping these definitions separate helps prevent errors when the same
concepts appear in biochemical structures or pathways.
,Question 3.
Which example is most consistent with chemiosmosis?
A. Ubiquinone diffusing in the membrane between large respiratory complexes.
B. A reduced nicotinamide cofactor entering respiration at the first complex.
C. Protons returning to the matrix through ATP synthase and driving phosphorylation of
ADP.
D. A urea-cycle intermediate crossing from the mitochondrial matrix to the cytosol.
Correct Answer: C. Protons returning to the matrix through ATP synthase and
driving phosphorylation of ADP.
Explanation: The defining feature is that Protons returning to the matrix through ATP
synthase and driving phosphorylation of ADP. is a representative example of
chemiosmosis. Chemiosmosis is the coupling of a transmembrane proton gradient to ATP
synthesis through proton flow down the electrochemical gradient. The other options were
drawn from related module concepts, but each illustrates a different biochemical feature.
Matching the defining feature to the example is the most reliable way to solve this type of
problem.
Question 4.
A student is distinguishing urea-cycle compartmentation from glutamate as nitrogen
collector. Which statement correctly describes urea-cycle compartmentation?
A. Glutamate commonly collects amino groups from many amino acids and can release
nitrogen through oxidative deamination.
B. Fumarate produced in the urea cycle can enter reactions linked to the citric acid cycle
through fumarate and malate metabolism.
C. The electron transport chain and ATP synthase are located in the inner mitochondrial
membrane, which is highly restrictive to proton movement.
D. The first two urea-cycle reactions occur in mitochondria and the remaining cyclic
reactions occur in the cytosol.
Correct Answer: D. The first two urea-cycle reactions occur in mitochondria and
the remaining cyclic reactions occur in the cytosol.
Explanation: The key point is that urea-cycle compartmentation should be defined as
follows: The first two urea-cycle reactions occur in mitochondria and the remaining cyclic
reactions occur in the cytosol. This differs from glutamate as nitrogen collector, which is
described by a separate set of properties. The distinction matters because substituting
one term for the other can change the predicted structure, location, or biochemical
outcome. The correct option therefore preserves the specific meaning of urea-cycle
compartmentation.
,Question 5.
Which example is most consistent with uncoupling?
A. Alanine transferring its amino group to alpha-ketoglutarate.
B. Protons leaking across the inner membrane instead of returning through ATP synthase.
C. The carrier amino acid cycling back for another turn of urea formation.
D. Ubiquinone diffusing in the membrane between large respiratory complexes.
Correct Answer: B. Protons leaking across the inner membrane instead of
returning through ATP synthase.
Explanation: The defining feature is that Protons leaking across the inner membrane
instead of returning through ATP synthase. is a representative example of uncoupling. An
uncoupler dissipates the proton gradient without directly stopping electron transport,
decreasing ATP synthesis and often increasing heat production. The other options were
drawn from related module concepts, but each illustrates a different biochemical feature.
Matching the defining feature to the example is the most reliable way to solve this type of
problem.
Question 6.
A student is reviewing key terms. Which statement correctly characterizes mitochondrial
urea-cycle steps?
A. Carbamoyl phosphate synthesis and citrulline formation are the mitochondrial portion of
the urea cycle.
B. Electrons associated with succinate-linked FADH2 enter the chain through Complex II
and therefore bypass proton pumping at Complex I.
C. Complex I accepts electrons from NADH, transfers them toward coenzyme Q, and
pumps protons across the inner mitochondrial membrane.
D. Argininosuccinate lyase cleaves argininosuccinate to arginine and fumarate.
Correct Answer: A. Carbamoyl phosphate synthesis and citrulline formation are
the mitochondrial portion of the urea cycle.
Explanation: This choice is correct because Carbamoyl phosphate synthesis and citrulline
formation are the mitochondrial portion of the urea cycle. That definition directly matches
the term named in the stem. By contrast, FADH2 electron entry refers to a different idea:
Electrons associated with succinate-linked FADH2 enter the chain through Complex II and
therefore bypass proton pumping at Complex I. Keeping these definitions separate helps
prevent errors when the same concepts appear in biochemical structures or pathways.
, Question 7.
Which option provides the strongest example of proton gradient?
A. A high-energy mitochondrial intermediate reacting with ornithine.
B. A soluble heme protein shuttling one electron at a time between two respiratory
complexes.
C. A mitochondrial reaction generating citrulline from ornithine.
D. Protons accumulating outside the mitochondrial matrix during electron transport.
Correct Answer: D. Protons accumulating outside the mitochondrial matrix
during electron transport.
Explanation: For this module, remember that Protons accumulating outside the
mitochondrial matrix during electron transport. is a representative example of proton
gradient. Respiration creates a higher proton concentration and more positive charge in
the intermembrane space relative to the matrix. The other options were drawn from
related module concepts, but each illustrates a different biochemical feature. Matching the
defining feature to the example is the most reliable way to solve this type of problem.
Question 8.
A student is distinguishing ATP yield from FADH2 from cytosolic urea-cycle steps. Which
statement correctly describes ATP yield from FADH2?
A. Citrulline is converted through argininosuccinate and arginine to urea in the cytosol.
B. Mitochondrial NADH donates electrons to Complex I, allowing proton pumping at
Complex I as well as downstream complexes.
C. A commonly used modern estimate is about 1.5 ATP per FADH2 because its electrons
enter at Complex II and bypass Complex I proton pumping.
D. Arginine is the immediate precursor of urea in the final hydrolytic step of the urea cycle.
Correct Answer: C. A commonly used modern estimate is about 1.5 ATP per
FADH2 because its electrons enter at Complex II and bypass Complex I proton
pumping.
Explanation: The key point is that ATP yield from FADH2 should be defined as follows: A
commonly used modern estimate is about 1.5 ATP per FADH2 because its electrons enter
at Complex II and bypass Complex I proton pumping. This differs from cytosolic urea-cycle
steps, which is described by a separate set of properties. The distinction matters because
substituting one term for the other can change the predicted structure, location, or
biochemical outcome. The correct option therefore preserves the specific meaning of ATP
yield from FADH2.
SET QUESTIONS WITH ANSWERS AND EXPLANATIONS
Question 1.
A learner wants an example of N-acetylglutamate. Which choice is best?
A. CPS I activity falling when its required activator is absent.
B. Protons accumulating outside the mitochondrial matrix during electron transport.
C. NADH oxidation coupled to proton translocation at the first ETC entry complex.
D. Severe hyperammonemia producing neurologic dysfunction.
Correct Answer: A. CPS I activity falling when its required activator is absent.
Explanation: For this module, remember that CPS I activity falling when its required
activator is absent. is a representative example of N-acetylglutamate. N-acetylglutamate
is an essential allosteric activator of mitochondrial carbamoyl phosphate synthetase I. The
other options were drawn from related module concepts, but each illustrates a different
biochemical feature. Matching the defining feature to the example is the most reliable way
to solve this type of problem.
Question 2.
A student is reviewing key terms. Which statement correctly characterizes
argininosuccinate lyase?
A. Nitrogen disposal pathways safely remove excess amino nitrogen, largely by converting
toxic ammonia into urea for excretion.
B. Argininosuccinate lyase cleaves argininosuccinate to arginine and fumarate.
C. Complexes I, III, and IV use electron-transfer energy to move protons from the matrix to
the intermembrane space; Complex II does not.
D. Complex IV transfers electrons from cytochrome c to oxygen, forms water, and
contributes to proton translocation.
Correct Answer: B. Argininosuccinate lyase cleaves argininosuccinate to
arginine and fumarate.
Explanation: This choice is correct because Argininosuccinate lyase cleaves
argininosuccinate to arginine and fumarate. That definition directly matches the term
named in the stem. By contrast, Complex IV refers to a different idea: Complex IV transfers
electrons from cytochrome c to oxygen, forms water, and contributes to proton
translocation. Keeping these definitions separate helps prevent errors when the same
concepts appear in biochemical structures or pathways.
,Question 3.
Which example is most consistent with chemiosmosis?
A. Ubiquinone diffusing in the membrane between large respiratory complexes.
B. A reduced nicotinamide cofactor entering respiration at the first complex.
C. Protons returning to the matrix through ATP synthase and driving phosphorylation of
ADP.
D. A urea-cycle intermediate crossing from the mitochondrial matrix to the cytosol.
Correct Answer: C. Protons returning to the matrix through ATP synthase and
driving phosphorylation of ADP.
Explanation: The defining feature is that Protons returning to the matrix through ATP
synthase and driving phosphorylation of ADP. is a representative example of
chemiosmosis. Chemiosmosis is the coupling of a transmembrane proton gradient to ATP
synthesis through proton flow down the electrochemical gradient. The other options were
drawn from related module concepts, but each illustrates a different biochemical feature.
Matching the defining feature to the example is the most reliable way to solve this type of
problem.
Question 4.
A student is distinguishing urea-cycle compartmentation from glutamate as nitrogen
collector. Which statement correctly describes urea-cycle compartmentation?
A. Glutamate commonly collects amino groups from many amino acids and can release
nitrogen through oxidative deamination.
B. Fumarate produced in the urea cycle can enter reactions linked to the citric acid cycle
through fumarate and malate metabolism.
C. The electron transport chain and ATP synthase are located in the inner mitochondrial
membrane, which is highly restrictive to proton movement.
D. The first two urea-cycle reactions occur in mitochondria and the remaining cyclic
reactions occur in the cytosol.
Correct Answer: D. The first two urea-cycle reactions occur in mitochondria and
the remaining cyclic reactions occur in the cytosol.
Explanation: The key point is that urea-cycle compartmentation should be defined as
follows: The first two urea-cycle reactions occur in mitochondria and the remaining cyclic
reactions occur in the cytosol. This differs from glutamate as nitrogen collector, which is
described by a separate set of properties. The distinction matters because substituting
one term for the other can change the predicted structure, location, or biochemical
outcome. The correct option therefore preserves the specific meaning of urea-cycle
compartmentation.
,Question 5.
Which example is most consistent with uncoupling?
A. Alanine transferring its amino group to alpha-ketoglutarate.
B. Protons leaking across the inner membrane instead of returning through ATP synthase.
C. The carrier amino acid cycling back for another turn of urea formation.
D. Ubiquinone diffusing in the membrane between large respiratory complexes.
Correct Answer: B. Protons leaking across the inner membrane instead of
returning through ATP synthase.
Explanation: The defining feature is that Protons leaking across the inner membrane
instead of returning through ATP synthase. is a representative example of uncoupling. An
uncoupler dissipates the proton gradient without directly stopping electron transport,
decreasing ATP synthesis and often increasing heat production. The other options were
drawn from related module concepts, but each illustrates a different biochemical feature.
Matching the defining feature to the example is the most reliable way to solve this type of
problem.
Question 6.
A student is reviewing key terms. Which statement correctly characterizes mitochondrial
urea-cycle steps?
A. Carbamoyl phosphate synthesis and citrulline formation are the mitochondrial portion of
the urea cycle.
B. Electrons associated with succinate-linked FADH2 enter the chain through Complex II
and therefore bypass proton pumping at Complex I.
C. Complex I accepts electrons from NADH, transfers them toward coenzyme Q, and
pumps protons across the inner mitochondrial membrane.
D. Argininosuccinate lyase cleaves argininosuccinate to arginine and fumarate.
Correct Answer: A. Carbamoyl phosphate synthesis and citrulline formation are
the mitochondrial portion of the urea cycle.
Explanation: This choice is correct because Carbamoyl phosphate synthesis and citrulline
formation are the mitochondrial portion of the urea cycle. That definition directly matches
the term named in the stem. By contrast, FADH2 electron entry refers to a different idea:
Electrons associated with succinate-linked FADH2 enter the chain through Complex II and
therefore bypass proton pumping at Complex I. Keeping these definitions separate helps
prevent errors when the same concepts appear in biochemical structures or pathways.
, Question 7.
Which option provides the strongest example of proton gradient?
A. A high-energy mitochondrial intermediate reacting with ornithine.
B. A soluble heme protein shuttling one electron at a time between two respiratory
complexes.
C. A mitochondrial reaction generating citrulline from ornithine.
D. Protons accumulating outside the mitochondrial matrix during electron transport.
Correct Answer: D. Protons accumulating outside the mitochondrial matrix
during electron transport.
Explanation: For this module, remember that Protons accumulating outside the
mitochondrial matrix during electron transport. is a representative example of proton
gradient. Respiration creates a higher proton concentration and more positive charge in
the intermembrane space relative to the matrix. The other options were drawn from
related module concepts, but each illustrates a different biochemical feature. Matching the
defining feature to the example is the most reliable way to solve this type of problem.
Question 8.
A student is distinguishing ATP yield from FADH2 from cytosolic urea-cycle steps. Which
statement correctly describes ATP yield from FADH2?
A. Citrulline is converted through argininosuccinate and arginine to urea in the cytosol.
B. Mitochondrial NADH donates electrons to Complex I, allowing proton pumping at
Complex I as well as downstream complexes.
C. A commonly used modern estimate is about 1.5 ATP per FADH2 because its electrons
enter at Complex II and bypass Complex I proton pumping.
D. Arginine is the immediate precursor of urea in the final hydrolytic step of the urea cycle.
Correct Answer: C. A commonly used modern estimate is about 1.5 ATP per
FADH2 because its electrons enter at Complex II and bypass Complex I proton
pumping.
Explanation: The key point is that ATP yield from FADH2 should be defined as follows: A
commonly used modern estimate is about 1.5 ATP per FADH2 because its electrons enter
at Complex II and bypass Complex I proton pumping. This differs from cytosolic urea-cycle
steps, which is described by a separate set of properties. The distinction matters because
substituting one term for the other can change the predicted structure, location, or
biochemical outcome. The correct option therefore preserves the specific meaning of ATP
yield from FADH2.
