AAMC Chemical and Physical Foundations Biological
Systems || A Verified A+ Pass.
What is the mechanical work done by the cantilever when the extension increases from 10 nm to
15 nm?
2.00 × 10-22 J
4.70 × 10-20 J
2.50 × 10-19 J
5.00 × 10-18 J correct answers This question requires you to apply the graphical method of
calculating the work done by a variable force, namely the elastic force, W = ksx2/2. Mechanical
work by an elastic force is W = ksx2/2 = Fx/2. Graphically, it is the area under the force-
extension graph between the corresponding data points. From Figure 2, the correct response is
{[(100 - 0) × 10-12]N ×[(15 - 10) × 10-9]m}/2 = 2.50 × 10-19 J.
What are the units for the rate constant ku discussed in the passage?
M-1•s-1
M•s
M•s-1
s-1 correct answers The protein unfolds by a unimolecular mechanism. The rate of unfolding has
units of M/s and is given by the expression Δ[unfolded protein length]/Δt = ku[folded protein
length]. The units of ku are therefore s-1.
What modification of Compound 1 will favor transport of Na+ relative to K+?
Replace X with CH3.
Replace Y with CH3.
Increase the ring size by adding one -CH2CH2O-.
Decrease the ring size by removing one -CH2CH2O-. correct answers From the passage, it was
stated that K+ is transported within the central portion of Compound 1. Since Na+ is chemically
similar to K+ it is reasonable to assume that there might be a way to favor its transport over K+
by changing the size of the ring. The change necessary would be to decrease the ring size since
Na+ is smaller than K+.
A compound has 5 chiral centers. How many possible stereoisomers does it have? correct
answers 32. 2^n
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 correct answers B. Precipitates occur when concentrations exceed Ksp
(solubility product constant)
,In the membrane of an axon in respect to its extracellular environment, which direction would
electric field lines be drawn? correct answers Pointing from extracellular fluid to the inside of the
axon membrane. Electric field lines exit from positive and enter negative charges. The axon is
negatively charged. The extracellular solution has a zero net potential.
Channel X transmits only the smallest substances dissolved in the extracellular fluid through the
axon membrane. Which substance does Channel X transmit?
A.Proteins
B.Sodium ions
C.Potassium ions
D.Chloride ions correct answers The answer to this question is B because sodium cations are the
smallest of the species listed. You can use the periodic table to establish that sodium ions are
smaller than either potassium or chloride ions
A nerve impulse lasts about 1ms. If the signal is conducted at 100 m/s, 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 correct answers 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.
What information about an axon is required to calculate the current associated with an NCV
pulse?
A.Conductivity, resistivity, and length
B.Potential, conductivity, and radius
C.Potential, resistivity, and radius
D.Potential, resistance per unit length, and length correct answers The answer to this question is
D. This is a question about Ohm's Law, I = V/R. To determine R, the resistance per unit length,
the length, and the potential V are needed.
The hydrogen ion concentration of the unknown aqueous solution was 1 × 10-5 M.
What was the pH of the unknown aqueous solution?
A.4
B.5
C.9
, D.10 correct answers 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.
A researcher attempted to identify an unknown AOm(OH)n compound. The compound
completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration
of the unknown aqueous solution was 1 × 10-5 M.
The unknown compound was probably a:
A.weak base.
B.strong base.
C.weak acid.
D.strong acid. correct answers The answer to this question is C because the hydrogen ion
concentration for this solution is greater than 1 × 10-7 but much less than the concentration of
the unknown compound itself. This means that the compound only partially ionized to form
hydrogen ions. This is behavior that defines a weak acid.
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. correct answers D. 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.
A researcher attempted to identify an unknown AOm(OH)n compound. The compound
completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration
of the unknown aqueous solution was 1 × 10-5 M.
It can be theorized that if the central atom, A, is an alkali or alkaline earth metal, the compound
is basic. But if A is a nonmetal, the compound is acidic.
The central atom, A, of the unknown compound was most likely:
A.an alkali or alkaline earth metal.
B.a transition metal.
C.a nonmetal.
D.a noble gas. correct answers The answer to this question is C because the compound produces
an acidic solution when dissolved. Compounds with the general formula AOm(OH)n are acids if
A is a non-metal.
Systems || A Verified A+ Pass.
What is the mechanical work done by the cantilever when the extension increases from 10 nm to
15 nm?
2.00 × 10-22 J
4.70 × 10-20 J
2.50 × 10-19 J
5.00 × 10-18 J correct answers This question requires you to apply the graphical method of
calculating the work done by a variable force, namely the elastic force, W = ksx2/2. Mechanical
work by an elastic force is W = ksx2/2 = Fx/2. Graphically, it is the area under the force-
extension graph between the corresponding data points. From Figure 2, the correct response is
{[(100 - 0) × 10-12]N ×[(15 - 10) × 10-9]m}/2 = 2.50 × 10-19 J.
What are the units for the rate constant ku discussed in the passage?
M-1•s-1
M•s
M•s-1
s-1 correct answers The protein unfolds by a unimolecular mechanism. The rate of unfolding has
units of M/s and is given by the expression Δ[unfolded protein length]/Δt = ku[folded protein
length]. The units of ku are therefore s-1.
What modification of Compound 1 will favor transport of Na+ relative to K+?
Replace X with CH3.
Replace Y with CH3.
Increase the ring size by adding one -CH2CH2O-.
Decrease the ring size by removing one -CH2CH2O-. correct answers From the passage, it was
stated that K+ is transported within the central portion of Compound 1. Since Na+ is chemically
similar to K+ it is reasonable to assume that there might be a way to favor its transport over K+
by changing the size of the ring. The change necessary would be to decrease the ring size since
Na+ is smaller than K+.
A compound has 5 chiral centers. How many possible stereoisomers does it have? correct
answers 32. 2^n
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 correct answers B. Precipitates occur when concentrations exceed Ksp
(solubility product constant)
,In the membrane of an axon in respect to its extracellular environment, which direction would
electric field lines be drawn? correct answers Pointing from extracellular fluid to the inside of the
axon membrane. Electric field lines exit from positive and enter negative charges. The axon is
negatively charged. The extracellular solution has a zero net potential.
Channel X transmits only the smallest substances dissolved in the extracellular fluid through the
axon membrane. Which substance does Channel X transmit?
A.Proteins
B.Sodium ions
C.Potassium ions
D.Chloride ions correct answers The answer to this question is B because sodium cations are the
smallest of the species listed. You can use the periodic table to establish that sodium ions are
smaller than either potassium or chloride ions
A nerve impulse lasts about 1ms. If the signal is conducted at 100 m/s, 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 correct answers 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.
What information about an axon is required to calculate the current associated with an NCV
pulse?
A.Conductivity, resistivity, and length
B.Potential, conductivity, and radius
C.Potential, resistivity, and radius
D.Potential, resistance per unit length, and length correct answers The answer to this question is
D. This is a question about Ohm's Law, I = V/R. To determine R, the resistance per unit length,
the length, and the potential V are needed.
The hydrogen ion concentration of the unknown aqueous solution was 1 × 10-5 M.
What was the pH of the unknown aqueous solution?
A.4
B.5
C.9
, D.10 correct answers 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.
A researcher attempted to identify an unknown AOm(OH)n compound. The compound
completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration
of the unknown aqueous solution was 1 × 10-5 M.
The unknown compound was probably a:
A.weak base.
B.strong base.
C.weak acid.
D.strong acid. correct answers The answer to this question is C because the hydrogen ion
concentration for this solution is greater than 1 × 10-7 but much less than the concentration of
the unknown compound itself. This means that the compound only partially ionized to form
hydrogen ions. This is behavior that defines a weak acid.
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. correct answers D. 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.
A researcher attempted to identify an unknown AOm(OH)n compound. The compound
completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration
of the unknown aqueous solution was 1 × 10-5 M.
It can be theorized that if the central atom, A, is an alkali or alkaline earth metal, the compound
is basic. But if A is a nonmetal, the compound is acidic.
The central atom, A, of the unknown compound was most likely:
A.an alkali or alkaline earth metal.
B.a transition metal.
C.a nonmetal.
D.a noble gas. correct answers The answer to this question is C because the compound produces
an acidic solution when dissolved. Compounds with the general formula AOm(OH)n are acids if
A is a non-metal.
