Princeton MCAT Exam #2 with
Accurate Solutions
What single change to the experimental system would reduce the electric field strength
necessary to maintain the oil drop in static equilibrium? - correct Answer-Decreasing the
mass of the drop
-When the oil drop (with charge -q) is in static eqbm, the electric force it feels, qE
upward, is balanced by the gravitational force, mg downward. Thus, qE = mg, so E =
mg / q. Don't be confused by the electric field strength in a capacitor, E = V / d.
Which of the following equations gives the voltage V necessary to maintain an oil
droplet of mass m and charge -q suspended in the region between Plates A and B,
which are separated by a distance d? - correct Answer-V = mgd / q
-The voltage V & the electric field strength E, between Plates A and B are related by the
equation V = Ed, where d is the distance between the plates. The oil drop is suspended
in the region between the plates when qE = mg or in terms of V, when q(V / d) = mg.
Solving this last equation for V gives V = mgd / q.
Which one of the following graphs best illustrates the relationship between a, an oil
drop's acceleration perpendicular to the plates, and E, the strength of the electric field
between the plates? - correct Answer-The net force on an oil drop (charge -q) between
Plates A and B is the difference between the electric force and the gravitational force:
Fnet = qE - mg. Since Fnet = ma, the acceleration of the oil drop is given by the
equation a = (q/m)E - g. This is an equation of the form "y = mx + b," whose graph is a
straight linear line with positive slope rising upwards
What best explains the variation among the values of the floating voltage for the
different droplets? - correct Answer-The charge of the droplets differs because the
amount of ionization due to the x-rays is random
-there is no way to control the exact number of excess electrons in the ionized air that
will cling to a falling oil droplet, but the net charge must be a whole number multiple of
the elementary charge.
What impact do the results shown in Figure 1 have on the hypothesis that leptin
resistance secondary to obesity reduces all effects of leptin? - correct Answer-Weakens
the hypothesis due to the increase in neural activity with injection of leptin in obese mice
,-given the dramatic increase in nerve activity with increasing leptin dosage, leptin does
have an impact on RSNA. Thus leptin resistance secondary to obesity does NOT
reduce ALL effects of leptin weakening q-stem hypothesis
A researcher proposed to block the leptin receptor in order to treat hypertension in
obese patients. Which of the following detection methods would work best to identify the
receptor in the different tissues affected by leptin? - correct Answer-western blot
-The leptin receptor is a protein and located in the cell membrane of different tissue
types. Detection of a protein can be done using a Western blot
Ghrelin, the "hunger hormone," is released when the stomach is empty. It increases
hunger and promotes secretion and motility in the digestive tract. The receptor for
ghrelin is found on the same cells in the brain as the receptor for leptin. Which of the
following is a true statement? - correct Answer-There is no interaction between leptin
and ghrelin because they operate on separate receptors
-they bind to the SAME cells in the brain, the fact that leptin and ghrelin bind to separate
receptors means that there cannot be any kind of inhibition or interaction between them.
They have seperate receptors, prevents any competitive inhibition.
Brown fat will increase energy expenditure in the form of heat better than any other
adipose tissue in the body. In brown fat, leptin indirectly activates uncoupling protein 1
(UCP-1) located in the inner mitochondrial membrane. UCP-1 activation will dissipate
the proton gradient across the inner mitochondrial membrane and STOP which of the
following reactions in mitochondria? - correct Answer-Oxidative phosphorylation
-absence of the proton gradient across the inner mitochondrial membrane no
electrochemical gradient has been built and the formation of ATP by ATP synthase, will
not proceed. The ETC will continue and pass electrons along the transport chain, but
the pumped protons will return to the matrix of the mitochondria with the help of UCP-1
activation
The structure of (+)-fructose is shown below:
How many chiral centers does (+)-fructose contain? - correct Answer-3 chiral centers
-Numbering from the TOP carbon down, C-3, C-4, and C-5 are chiral centers because
they each have four different substituents
Creatine phosphate is a high-energy buffer that helps maintain the level of available
high-energy phosphates such as ATP. During intense muscular exertion, creatine
phosphate replenishes the muscle's ATP by releasing a relatively larger amount of
energy in transferring its phosphate group to ADP. ATP is able to accept this phosphate
group from creatinine phosphate and serve as a convenient carrier of energy because: -
correct Answer-it has phosphate groups with an intermediate transfer potential
,-ATP is good energy carrier bc it has an intermediate transfer potential. This allows
higher energy phosphate carriers (creatine phosphate) to drive the synthesis of ATP by
transferring their P-groups to ADP
ATP - correct Answer-a particularly good energy carrier bc it has an intermediate
transfer potential which allows higher energy phosphate carriers (like creatine
phosphate) to drive the synthesis of ATP by transferring their phosphate groups to ADP
has a varied role in the body, as an energy carrier and also as a nucleotide for RNA and
DNA
is present in every cell in the body
Rank the following bonds in order of increasing polarity:
C—Cl
Cl—Cl
Si—Cl
P—Cl - correct Answer-Cl-Cl < C-Cl < P-Cl < Si-Cl
-polarity of a bond depends on the difference in EN between the 2 bonding atoms: The
larger the difference, the more unequal the sharing of electrons, the more polar. the Cl
—Cl bond is completely nonpolar. Carbon is more EN than Si, therefore Cl, which is the
most EN element depicted, will show the greatest EN difference with Si. Therefore the
Si—Cl bond is most polar
The sound level of a sound wave that is striking an eardrum is increased from 35 dB to
55 dB. By what factor has the intensity of the sound increased? - correct Answer-100
-each increase by 10 in the decibel level, the intensity of the sound increases by a factor
of 10. the decibel level has increased by 2 units of 10 (since 55 - 35 = 20 = 10 + 10), so
the intensity increases by two factors of 10, 10^2 = 100.
The ratio of products to reactants at equilibrium for Reaction 1 will change with a
change in the: - correct Answer-temperature
-only way to change a reaction's equilibrium constant is to change the temperature.
in the forward direction, Reaction 1 may be considered:
ATP + glutamate + NH3 => ADP + phosphate + glutamine - correct Answer-favorable,
because the negative ΔG° for Reaction 2 more than compensates for the positive ΔG°
for Reaction 3.
-ΔG°2 + ΔG°3 < 0, so the overall reaction would be favorable and still be negative when
added together
G2= -3I
G3= 14
, Which of the following is true for Reaction 2, once it is allowed sufficient time to achieve
equilibrium?
ATP + H2O => ADP + phosphate ΔG° = -30.5 kJ/mol - correct Answer-ΔG > ΔG°
-At equilibrium ΔG = 0. Since reaction 2 has a negative value of ΔG°, then ΔG > ΔG°
In Reaction 1, the compound glutamine synthetase serves to:
ATP + glutamate + NH3 => ADP + phosphate + glutamine - correct Answer-decrease
the activation energy
-catalyzed by the enzyme glutamine synthetase which catalyst increases the rate of a
rxn by decreasing the Ea.
Hypothetically, if Reaction I was found to be spontaneous at standard state and higher
temperatures, but nonspontaneous at low temperatures, the reaction must result in: -
correct Answer-increasing entropy and increasing enthalpy
-From the equation ΔG = ΔH - TΔS, ΔH > 0 and ΔS < 0 would always give ΔG > 0
(nonspontaneous) no matter what the temperature. a ΔH < 0 and ΔS > 0 would give ΔG
< 0 (spontaneous) regardless of temperature.
-increasing both H & increasing S but at low temps would give +G
Which one of the following expressions is equal to the pressure difference between
Point c and Point d? - correct Answer-(ρliquid)gy
-difference in pressure between two points in a static fluid is given by the expression
where y is the vertical distance between the two points
A healthy woman has a respiratory minute volume (the amount of air inhaled and
exhaled in one minute) of about 6 L. Suppose the breathing tube she uses has a cross-
sectional area of 1 cm2. What is the average flow speed through the tube? - correct
Answer-1 m/s
-volume flow rate (volume of air flowing per second) is f = Av. The flow rate in this case
is f = 6 L/min × (1 m L) × (1 min / 60 s) = 1 × 10-4 m3/s. The cross-sectional
area is 1 cm2 × (1 m / 100 cm)2 = 10-4 m2. Thus v = f / A = (1 × 10-4 m3/s) / (10-4 m2)
= 1 m/s
-solve for v in FAv eqn
volume flow rate - correct Answer-volume of air flowing per second
f= Av
If the alcohol in the Pitot tube were replaced with water, then the height difference of the
liquid in the U-tube for a given air speed would be: - correct Answer-smaller
Accurate Solutions
What single change to the experimental system would reduce the electric field strength
necessary to maintain the oil drop in static equilibrium? - correct Answer-Decreasing the
mass of the drop
-When the oil drop (with charge -q) is in static eqbm, the electric force it feels, qE
upward, is balanced by the gravitational force, mg downward. Thus, qE = mg, so E =
mg / q. Don't be confused by the electric field strength in a capacitor, E = V / d.
Which of the following equations gives the voltage V necessary to maintain an oil
droplet of mass m and charge -q suspended in the region between Plates A and B,
which are separated by a distance d? - correct Answer-V = mgd / q
-The voltage V & the electric field strength E, between Plates A and B are related by the
equation V = Ed, where d is the distance between the plates. The oil drop is suspended
in the region between the plates when qE = mg or in terms of V, when q(V / d) = mg.
Solving this last equation for V gives V = mgd / q.
Which one of the following graphs best illustrates the relationship between a, an oil
drop's acceleration perpendicular to the plates, and E, the strength of the electric field
between the plates? - correct Answer-The net force on an oil drop (charge -q) between
Plates A and B is the difference between the electric force and the gravitational force:
Fnet = qE - mg. Since Fnet = ma, the acceleration of the oil drop is given by the
equation a = (q/m)E - g. This is an equation of the form "y = mx + b," whose graph is a
straight linear line with positive slope rising upwards
What best explains the variation among the values of the floating voltage for the
different droplets? - correct Answer-The charge of the droplets differs because the
amount of ionization due to the x-rays is random
-there is no way to control the exact number of excess electrons in the ionized air that
will cling to a falling oil droplet, but the net charge must be a whole number multiple of
the elementary charge.
What impact do the results shown in Figure 1 have on the hypothesis that leptin
resistance secondary to obesity reduces all effects of leptin? - correct Answer-Weakens
the hypothesis due to the increase in neural activity with injection of leptin in obese mice
,-given the dramatic increase in nerve activity with increasing leptin dosage, leptin does
have an impact on RSNA. Thus leptin resistance secondary to obesity does NOT
reduce ALL effects of leptin weakening q-stem hypothesis
A researcher proposed to block the leptin receptor in order to treat hypertension in
obese patients. Which of the following detection methods would work best to identify the
receptor in the different tissues affected by leptin? - correct Answer-western blot
-The leptin receptor is a protein and located in the cell membrane of different tissue
types. Detection of a protein can be done using a Western blot
Ghrelin, the "hunger hormone," is released when the stomach is empty. It increases
hunger and promotes secretion and motility in the digestive tract. The receptor for
ghrelin is found on the same cells in the brain as the receptor for leptin. Which of the
following is a true statement? - correct Answer-There is no interaction between leptin
and ghrelin because they operate on separate receptors
-they bind to the SAME cells in the brain, the fact that leptin and ghrelin bind to separate
receptors means that there cannot be any kind of inhibition or interaction between them.
They have seperate receptors, prevents any competitive inhibition.
Brown fat will increase energy expenditure in the form of heat better than any other
adipose tissue in the body. In brown fat, leptin indirectly activates uncoupling protein 1
(UCP-1) located in the inner mitochondrial membrane. UCP-1 activation will dissipate
the proton gradient across the inner mitochondrial membrane and STOP which of the
following reactions in mitochondria? - correct Answer-Oxidative phosphorylation
-absence of the proton gradient across the inner mitochondrial membrane no
electrochemical gradient has been built and the formation of ATP by ATP synthase, will
not proceed. The ETC will continue and pass electrons along the transport chain, but
the pumped protons will return to the matrix of the mitochondria with the help of UCP-1
activation
The structure of (+)-fructose is shown below:
How many chiral centers does (+)-fructose contain? - correct Answer-3 chiral centers
-Numbering from the TOP carbon down, C-3, C-4, and C-5 are chiral centers because
they each have four different substituents
Creatine phosphate is a high-energy buffer that helps maintain the level of available
high-energy phosphates such as ATP. During intense muscular exertion, creatine
phosphate replenishes the muscle's ATP by releasing a relatively larger amount of
energy in transferring its phosphate group to ADP. ATP is able to accept this phosphate
group from creatinine phosphate and serve as a convenient carrier of energy because: -
correct Answer-it has phosphate groups with an intermediate transfer potential
,-ATP is good energy carrier bc it has an intermediate transfer potential. This allows
higher energy phosphate carriers (creatine phosphate) to drive the synthesis of ATP by
transferring their P-groups to ADP
ATP - correct Answer-a particularly good energy carrier bc it has an intermediate
transfer potential which allows higher energy phosphate carriers (like creatine
phosphate) to drive the synthesis of ATP by transferring their phosphate groups to ADP
has a varied role in the body, as an energy carrier and also as a nucleotide for RNA and
DNA
is present in every cell in the body
Rank the following bonds in order of increasing polarity:
C—Cl
Cl—Cl
Si—Cl
P—Cl - correct Answer-Cl-Cl < C-Cl < P-Cl < Si-Cl
-polarity of a bond depends on the difference in EN between the 2 bonding atoms: The
larger the difference, the more unequal the sharing of electrons, the more polar. the Cl
—Cl bond is completely nonpolar. Carbon is more EN than Si, therefore Cl, which is the
most EN element depicted, will show the greatest EN difference with Si. Therefore the
Si—Cl bond is most polar
The sound level of a sound wave that is striking an eardrum is increased from 35 dB to
55 dB. By what factor has the intensity of the sound increased? - correct Answer-100
-each increase by 10 in the decibel level, the intensity of the sound increases by a factor
of 10. the decibel level has increased by 2 units of 10 (since 55 - 35 = 20 = 10 + 10), so
the intensity increases by two factors of 10, 10^2 = 100.
The ratio of products to reactants at equilibrium for Reaction 1 will change with a
change in the: - correct Answer-temperature
-only way to change a reaction's equilibrium constant is to change the temperature.
in the forward direction, Reaction 1 may be considered:
ATP + glutamate + NH3 => ADP + phosphate + glutamine - correct Answer-favorable,
because the negative ΔG° for Reaction 2 more than compensates for the positive ΔG°
for Reaction 3.
-ΔG°2 + ΔG°3 < 0, so the overall reaction would be favorable and still be negative when
added together
G2= -3I
G3= 14
, Which of the following is true for Reaction 2, once it is allowed sufficient time to achieve
equilibrium?
ATP + H2O => ADP + phosphate ΔG° = -30.5 kJ/mol - correct Answer-ΔG > ΔG°
-At equilibrium ΔG = 0. Since reaction 2 has a negative value of ΔG°, then ΔG > ΔG°
In Reaction 1, the compound glutamine synthetase serves to:
ATP + glutamate + NH3 => ADP + phosphate + glutamine - correct Answer-decrease
the activation energy
-catalyzed by the enzyme glutamine synthetase which catalyst increases the rate of a
rxn by decreasing the Ea.
Hypothetically, if Reaction I was found to be spontaneous at standard state and higher
temperatures, but nonspontaneous at low temperatures, the reaction must result in: -
correct Answer-increasing entropy and increasing enthalpy
-From the equation ΔG = ΔH - TΔS, ΔH > 0 and ΔS < 0 would always give ΔG > 0
(nonspontaneous) no matter what the temperature. a ΔH < 0 and ΔS > 0 would give ΔG
< 0 (spontaneous) regardless of temperature.
-increasing both H & increasing S but at low temps would give +G
Which one of the following expressions is equal to the pressure difference between
Point c and Point d? - correct Answer-(ρliquid)gy
-difference in pressure between two points in a static fluid is given by the expression
where y is the vertical distance between the two points
A healthy woman has a respiratory minute volume (the amount of air inhaled and
exhaled in one minute) of about 6 L. Suppose the breathing tube she uses has a cross-
sectional area of 1 cm2. What is the average flow speed through the tube? - correct
Answer-1 m/s
-volume flow rate (volume of air flowing per second) is f = Av. The flow rate in this case
is f = 6 L/min × (1 m L) × (1 min / 60 s) = 1 × 10-4 m3/s. The cross-sectional
area is 1 cm2 × (1 m / 100 cm)2 = 10-4 m2. Thus v = f / A = (1 × 10-4 m3/s) / (10-4 m2)
= 1 m/s
-solve for v in FAv eqn
volume flow rate - correct Answer-volume of air flowing per second
f= Av
If the alcohol in the Pitot tube were replaced with water, then the height difference of the
liquid in the U-tube for a given air speed would be: - correct Answer-smaller
