MCAT - AAMC - Practice Exam 3 Study Guide Questions &
Answers 2024.
Compound 1 is used to treat HIV infection based on its ability to act as:
A. an agonist.
B. an antagonist.
C. a placebo.
D. a catalyst.
B.
This is a Biochemistry question that falls under content category “Principles of chemical
thermodynamics and kinetics.” The answer to this question is B because
Compound 1 binds to the transition state of HIV protease and serves to treat infection. It
is clearly inhibiting this enzyme through its binding and thus serves as an
antagonist. This question requires Knowledge of Scientific Concepts and Principles,
specifically the definition of an antagonist, to arrive at the answer.
"One such molecule is Compound 1, shown in Figure 2, which is a potent HIV protease
inhibitor."
How many stereoisomers of Compound 1 exist?
A. 8
B. 16
C. 32
D. 64
C.
This is an Organic Chemistry question that falls under the content category “Nature of
molecules and intermolecular interactions.” The answer to this question is C. There are
5 chirality centers in Compound 1. By application of the 2n rule, there are 32 possible
stereoisomers. This question requires Scientific Reasoning and Problem Solving to
arrive at the answer.
Why do kidney stones form in some individuals treated with Compound 1?
A. [Ca2+] + [C2O42–] > Ksp
B. [Ca2+][C2O42–] > Ksp
C. [Ca2+] + [C2O42–] < Ksp
D. [Ca2+][C2O42–] < Ksp
B.
This is a General Chemistry question that falls under the content category “Unique
nature of water and its solutions.” The answer to this question is B because calcium
oxalate precipitates when [Ca2+][C2O42–] exceeds the solubility product constant Ksp
by definition. This question requires Scientific Reasoning and Problem Solving to arrive
at the answer.
The peptide bond between which two amino acid residues is cleaved by HIV
protease?
A. Phe and Ala
,B. Pro and Val
C. Val and Ala
D. Phe and Pro
D.
This is a Biochemistry question that falls under the content category "Structure, function,
and reactivity of biologically relevant molecules." The answer to this question is D based
on the depiction shown in Figure 1. The peptide bond cleaved in Figure 1 is between
phenylalanine and proline (Phe and Pro). This question requires Knowledge of Scientific
Concepts and Principles, the knowledge of the structures of phenylalanine and proline,
to arrive at the answer.
Which image best illustrates the electric field lines between the inside of an axon
and the surrounding extracellular solution?
B.
This is a Physics question that falls under content category "Electrochemistry and
electrical circuits and their elements." The answer to this question is B because the
electric field lines exit from positive and enter negative charges. The axon is negatively
charged. The extracellular solution has a zero net potential. It is a Knowledge of
Scientific Concepts and Principles question because the examinee must identify the
relationship between the distribution of electric charges in the axon and the electric field
lines they produce.
What is the closest distance the electrodes used in an NCV test can be placed on
a nerve in order to measure the voltage change as a response to the stimulus?
A. 0.01 m
B. 0.1 m
C. 1.0 m
D. 10 m
B.
This is a Physics question that falls under content category "Translational motion,
forces, work, energy, and equilibrium in living systems." The answer to this question is B
because the shortest time duration that can be detected is not less than the action
potential time response of 1 msec, according to Figure 1. The distance travelled by the
impulse during this time is 1 msec × 100 m/s = 0.1 m, which is the closest distance the
electrodes must be placed on the nerve. This question requires Scientific Reasoning
and Problem-Solving, correct determination and use of a scientific formula, in order to
arrive at the answer.
What was the pH of the unknown aqueous solution?
A. 4
B. 5
C. 9
D. 10
B.
This is a General Chemistry question that falls under the content category “Unique
nature of water and its solutions.” The answer to this question is B because the pH of
the solution is, by definition, –log([H+]). Since the hydrogen ion concentration for the
unknown aqueous solution was given as 1 × 10–5, the pH of this solution is 5. This
question requires Scientific Reasoning and Problem Solving to arrive at the answer.
, "The hydrogen ion concentration of the unknown aqueous solution was 1 × 10–5 M."
Two additional compounds were studied: NO2(OH) dissolved in water and
produced an acidic solution, and Ni(OH)2 dissolved only in an acidic solution.
What type of compounds were these?
A. Both were oxyacids.
B. Both were bases.
C. NO2(OH) was a base and Ni(OH)2 was an oxyacid.
D. NO2(OH) was an oxyacid and Ni(OH)2 was a base.
D.
This is a General Chemistry question that falls under the content category "Unique
nature of water and its solutions." The answer to this question is D. The first substance
is nitric acid, HNO3. Since this substance dissolves to generate an acidic solution, the
bond between O and H in the structural formula NO2OH breaks when the substance
dissolves, making it an oxyacid. The latter substance, Ni(OH)2, is apparently insoluble
in neutral water, but will dissolve if the solution is acidic. This behavior is typical of
substances that feature basic anions. The bond between Ni and O is the one that
breaks when Ni(OH)2 dissolves. The hydroxide ion that is produced quickly reacts with
protons in solution and cannot react again with Ni2+ to form a precipitate. This question
requires Knowledge of Scientific Concepts and Principles to arrive at the answer.
What is the concentration of Cl- ions in a 0.1 M solution of calcium chloride?
A. 0.02 M
B. 0.05 M
C. 0.10 M
D. 0.20 M
D.
This is a General Chemistry question that falls under the content category "Unique
nature of water and its solutions." The answer to this question is D because the formula
for calcium chloride is CaCl2 and it produces twice as many Cl- ions as Ca2+ ions in
solution when it dissolves. This question requires Knowledge of Scientific Concepts and
Principles, the nature of ionic solutes when they dissolve in water, to arrive at the
answer.
What is the net charge of the peptide Arg-Ala-Phe-Leu at pH 8?
A. -1
B. 0
C. +1
D. +2
C.
This is a Biochemistry question that falls under the content category “Structure, function,
and reactivity of biologically-relevant molecules.” The answer is C because the net
charge is equal to the sum of all charged portions of the peptide. The N-terminus
contributes a +1 charge along with the Arg side chain. The C-terminus contributes a –1
charge, so the net charge is +1. This is a Scientific Reasoning and Problem Solving
question because you must identify the appropriate charge of each functional group at a
given pH and apply that knowledge to the calculation of net charge.
Answers 2024.
Compound 1 is used to treat HIV infection based on its ability to act as:
A. an agonist.
B. an antagonist.
C. a placebo.
D. a catalyst.
B.
This is a Biochemistry question that falls under content category “Principles of chemical
thermodynamics and kinetics.” The answer to this question is B because
Compound 1 binds to the transition state of HIV protease and serves to treat infection. It
is clearly inhibiting this enzyme through its binding and thus serves as an
antagonist. This question requires Knowledge of Scientific Concepts and Principles,
specifically the definition of an antagonist, to arrive at the answer.
"One such molecule is Compound 1, shown in Figure 2, which is a potent HIV protease
inhibitor."
How many stereoisomers of Compound 1 exist?
A. 8
B. 16
C. 32
D. 64
C.
This is an Organic Chemistry question that falls under the content category “Nature of
molecules and intermolecular interactions.” The answer to this question is C. There are
5 chirality centers in Compound 1. By application of the 2n rule, there are 32 possible
stereoisomers. This question requires Scientific Reasoning and Problem Solving to
arrive at the answer.
Why do kidney stones form in some individuals treated with Compound 1?
A. [Ca2+] + [C2O42–] > Ksp
B. [Ca2+][C2O42–] > Ksp
C. [Ca2+] + [C2O42–] < Ksp
D. [Ca2+][C2O42–] < Ksp
B.
This is a General Chemistry question that falls under the content category “Unique
nature of water and its solutions.” The answer to this question is B because calcium
oxalate precipitates when [Ca2+][C2O42–] exceeds the solubility product constant Ksp
by definition. This question requires Scientific Reasoning and Problem Solving to arrive
at the answer.
The peptide bond between which two amino acid residues is cleaved by HIV
protease?
A. Phe and Ala
,B. Pro and Val
C. Val and Ala
D. Phe and Pro
D.
This is a Biochemistry question that falls under the content category "Structure, function,
and reactivity of biologically relevant molecules." The answer to this question is D based
on the depiction shown in Figure 1. The peptide bond cleaved in Figure 1 is between
phenylalanine and proline (Phe and Pro). This question requires Knowledge of Scientific
Concepts and Principles, the knowledge of the structures of phenylalanine and proline,
to arrive at the answer.
Which image best illustrates the electric field lines between the inside of an axon
and the surrounding extracellular solution?
B.
This is a Physics question that falls under content category "Electrochemistry and
electrical circuits and their elements." The answer to this question is B because the
electric field lines exit from positive and enter negative charges. The axon is negatively
charged. The extracellular solution has a zero net potential. It is a Knowledge of
Scientific Concepts and Principles question because the examinee must identify the
relationship between the distribution of electric charges in the axon and the electric field
lines they produce.
What is the closest distance the electrodes used in an NCV test can be placed on
a nerve in order to measure the voltage change as a response to the stimulus?
A. 0.01 m
B. 0.1 m
C. 1.0 m
D. 10 m
B.
This is a Physics question that falls under content category "Translational motion,
forces, work, energy, and equilibrium in living systems." The answer to this question is B
because the shortest time duration that can be detected is not less than the action
potential time response of 1 msec, according to Figure 1. The distance travelled by the
impulse during this time is 1 msec × 100 m/s = 0.1 m, which is the closest distance the
electrodes must be placed on the nerve. This question requires Scientific Reasoning
and Problem-Solving, correct determination and use of a scientific formula, in order to
arrive at the answer.
What was the pH of the unknown aqueous solution?
A. 4
B. 5
C. 9
D. 10
B.
This is a General Chemistry question that falls under the content category “Unique
nature of water and its solutions.” The answer to this question is B because the pH of
the solution is, by definition, –log([H+]). Since the hydrogen ion concentration for the
unknown aqueous solution was given as 1 × 10–5, the pH of this solution is 5. This
question requires Scientific Reasoning and Problem Solving to arrive at the answer.
, "The hydrogen ion concentration of the unknown aqueous solution was 1 × 10–5 M."
Two additional compounds were studied: NO2(OH) dissolved in water and
produced an acidic solution, and Ni(OH)2 dissolved only in an acidic solution.
What type of compounds were these?
A. Both were oxyacids.
B. Both were bases.
C. NO2(OH) was a base and Ni(OH)2 was an oxyacid.
D. NO2(OH) was an oxyacid and Ni(OH)2 was a base.
D.
This is a General Chemistry question that falls under the content category "Unique
nature of water and its solutions." The answer to this question is D. The first substance
is nitric acid, HNO3. Since this substance dissolves to generate an acidic solution, the
bond between O and H in the structural formula NO2OH breaks when the substance
dissolves, making it an oxyacid. The latter substance, Ni(OH)2, is apparently insoluble
in neutral water, but will dissolve if the solution is acidic. This behavior is typical of
substances that feature basic anions. The bond between Ni and O is the one that
breaks when Ni(OH)2 dissolves. The hydroxide ion that is produced quickly reacts with
protons in solution and cannot react again with Ni2+ to form a precipitate. This question
requires Knowledge of Scientific Concepts and Principles to arrive at the answer.
What is the concentration of Cl- ions in a 0.1 M solution of calcium chloride?
A. 0.02 M
B. 0.05 M
C. 0.10 M
D. 0.20 M
D.
This is a General Chemistry question that falls under the content category "Unique
nature of water and its solutions." The answer to this question is D because the formula
for calcium chloride is CaCl2 and it produces twice as many Cl- ions as Ca2+ ions in
solution when it dissolves. This question requires Knowledge of Scientific Concepts and
Principles, the nature of ionic solutes when they dissolve in water, to arrive at the
answer.
What is the net charge of the peptide Arg-Ala-Phe-Leu at pH 8?
A. -1
B. 0
C. +1
D. +2
C.
This is a Biochemistry question that falls under the content category “Structure, function,
and reactivity of biologically-relevant molecules.” The answer is C because the net
charge is equal to the sum of all charged portions of the peptide. The N-terminus
contributes a +1 charge along with the Arg side chain. The C-terminus contributes a –1
charge, so the net charge is +1. This is a Scientific Reasoning and Problem Solving
question because you must identify the appropriate charge of each functional group at a
given pH and apply that knowledge to the calculation of net charge.
