MCAT Practice Test 13 with Complete
Solutions
How do you know the dehydration of maleic acid to fumaric acid is stereospecific? -
ANS--The fact that both fumaric and maleic acid are produced means that the
dehydration of malic acid is not stereospecific
-In addition, the reaction occurs most readily with tertiary alcohols
-It involves the loss of a water molecule
-The reaction has a carbocation intermediate
In an sn2 reaction that involves 1-pentanol, why would happen if you replaced it with 2-
pentanol - ANS--The rate of substitution would be less
-There is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of
1-pentanol
-The rate of substitution of protonated alcohols is subject to steric hindrance. This
inhibits the ability of nucleophiles to collide with reacting electrophilic center and slows
the rate of reaction
In a solution containing 2-methyl-2-butanol, 2-methyl-2-butene, 2-chloro-2-methylbutane
and 2-bromo-methylbutane, it is injected into a gas-liquid chromatograph, the first peak
observed in the gc trace is attributable to which compound? - ANS--2-methyl-2-butene
-This exhibits the lowest molecular weight and also the weakest intermolecular forces of
attraction. This substance will therefore migrate fastest and be the first peak in the gas
chromatograph (gc) trace
What is the easiest way to decrease the percentage ionization of 1.0 M acetic acid,
CH3CO2H? - ANS--Adding concentrated HCl
-HCl is a strong acid that will increase the amount of H+ in solution and thus decrease
the percentage of CH3CO2H that ionizes
The intensity of radiation emitted by the oxygen sensor is directly proportional to what? -
ANS--The number of photons emitted
-The energy of electromagnetic radiation is directly proportional to the number of
photons, and the intensity of electromagnetic radiation is defined as energy emitted per
unit time
-Intensity is directly proportional to the number of photons emitted
What is the energy of the photons emitted by the LED at a frequency of 610 THz (h= 6.6
x 10^-34 J*s) - ANS--4.0 x 10^-19
-The energy of a photon frequency is E=hf
E= (6.6 E -34) x (610 x 10^12)=
,4 E -19
The maximum and minimum blood pressures of a healthy adult (the systolic Ps and
diastolic Pd pressures, respectively) are about Ps= 120 mmHg and Pd= 75 mmHg
The pulse pressure Pp is defined as:
Pp= Ps- Pd
What percentage of standard atmospheric pressure is the pulse pressure of a healthy
adult? - ANS--The pulse pressure in a healthy adult is 120mmHg -75mmHg = 45 mmHg
45mmHg/750mmHg= 6%
How to find work from power generated? - ANS--(Power) x (time in seconds)= joules of
energy
-If you find that the movement of 9L of blood through a brachial artery occurs in 10
minutes, and that correlates to 200 W of power, you multiply 200W x 600 seconds= 120
kJ
Iodine reaction with thiol group - ANS--Leads to the formation of a disulfide and when a
thiol is part of a large molecule, it forms a disulfide linkage
-This is a form of intermolecular covalent bonding
On what amino acid does phosphorylation occur? - ANS-Serine
Why is the velocity of blood flow slower in capillaries than in arteries? - ANS--The total
cross sectional area of capillaries exceeds that of arteries
-The high number of capillaries in the body means that the total cross-sectional area of
these vessels is larger than any other type in the circulatory system. This causes the
blood velocity to decrease
Human rhodopsin is a g protein-coupled receptor found in rod cells in the retina.
Rhodopsin is composed of opsin, a family of seven helix transmembrane proteins and a
covalently attached coenzyme, retinal
The production of a variety of opsins function to do what? - ANS--Enable the detection
of different colors
-The wavelength of light absorbed by a molecule depends on its structure, and so the
production of a variety of structurally related opsins functions to enable the detection of
different colors
Which reaction is catalyzed from protein lysosomal lipase (LipA)? - ANS--Hydrolysis of
triacylglycerides
-The LipA is a lipase, which means it must hydrolyze fatty acids.
What type of bond is formed by glycogen synthase upon release of UDP? - ANS-alpha-
1,4- glycosidic bond
Beta - decay - ANS-radioactive decay of an atomic nucleus that is accompanied by the
emission of a beta particle
, What is a homogenous catalyst - ANS--A catalyst in the same phase as the reactants
-If it cannot separate from the products at the end of a reaction, the products will be
contaminated.
What is a heterogenous catalyst - ANS-A catalyst that is in a different phase from the
reactants
How will the rate of a catalyzed reaction be affected if the solid catalyst is finely ground
before it is added to the reaction mixture? - ANS--The rate will be faster because a
greater surface area of catalyst will be exposed
-Grinding a hetergeneous catalyst increases the amount of catalyst available to the
reaction and therefore increases its rate
How can you determine from the electric potential if a reaction will be spontaneous? -
ANS--If a reaction is spontaneous, than the electric potential (E) will be greater than
zero (positive)
BaCrO4 (s) -> Ba^2+(aq) + CrO4^2-(aq)
This exists in a saturated aqueous solution of BaCrO4. The addition of Na2CrO4 in a
saturated BaCrO4 solution would do what? - ANS--This will cause the equilibrium to
shift to the left
-The dissolution of Na2CrO4 would introduce the common ion, CrO4^2-, which would
reduce the solubility of BaCrO4 due to the common ion effect
Epilepsy may result in motor seizures due to massive synchronous firing of neurons in a
small area of the cerebral cortex (the epileptic focus). The excitation spreads from the
focus, involving an increasingly larger area of the cortex. A drug for the treatment of
epilepsy would be most effective if it caused what changes in epileptic focus? - ANS--An
increase in neuron firing threshold
-A drug that would best treat epilepsy, should reduce the activity of the neurons in the
epileptic focus, which are excitatory neurons based on their effect throughout the cortex
-Increasing the threshold required to generate an action potential would decrease the
chance that individual neurons would fire, thus reducing the overall amount of excitation
that spreads from the epileptic focus throughout the cortex
What are three ways to measure the activity of the Na+ K+ ATPase? - ANS--Measuring
the rate of ATP hydrolysis
-Measuring the rate of ADP production
-Measuring the change in ion concentration within the liposome
Why does measuring the free energy change of the ion transport not determine activity
of Na+ K+ ATPase? - ANS--Free energy is a thermodynamic quantity and is not a
kinetic property. Activity is a kinetic property
Solutions
How do you know the dehydration of maleic acid to fumaric acid is stereospecific? -
ANS--The fact that both fumaric and maleic acid are produced means that the
dehydration of malic acid is not stereospecific
-In addition, the reaction occurs most readily with tertiary alcohols
-It involves the loss of a water molecule
-The reaction has a carbocation intermediate
In an sn2 reaction that involves 1-pentanol, why would happen if you replaced it with 2-
pentanol - ANS--The rate of substitution would be less
-There is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of
1-pentanol
-The rate of substitution of protonated alcohols is subject to steric hindrance. This
inhibits the ability of nucleophiles to collide with reacting electrophilic center and slows
the rate of reaction
In a solution containing 2-methyl-2-butanol, 2-methyl-2-butene, 2-chloro-2-methylbutane
and 2-bromo-methylbutane, it is injected into a gas-liquid chromatograph, the first peak
observed in the gc trace is attributable to which compound? - ANS--2-methyl-2-butene
-This exhibits the lowest molecular weight and also the weakest intermolecular forces of
attraction. This substance will therefore migrate fastest and be the first peak in the gas
chromatograph (gc) trace
What is the easiest way to decrease the percentage ionization of 1.0 M acetic acid,
CH3CO2H? - ANS--Adding concentrated HCl
-HCl is a strong acid that will increase the amount of H+ in solution and thus decrease
the percentage of CH3CO2H that ionizes
The intensity of radiation emitted by the oxygen sensor is directly proportional to what? -
ANS--The number of photons emitted
-The energy of electromagnetic radiation is directly proportional to the number of
photons, and the intensity of electromagnetic radiation is defined as energy emitted per
unit time
-Intensity is directly proportional to the number of photons emitted
What is the energy of the photons emitted by the LED at a frequency of 610 THz (h= 6.6
x 10^-34 J*s) - ANS--4.0 x 10^-19
-The energy of a photon frequency is E=hf
E= (6.6 E -34) x (610 x 10^12)=
,4 E -19
The maximum and minimum blood pressures of a healthy adult (the systolic Ps and
diastolic Pd pressures, respectively) are about Ps= 120 mmHg and Pd= 75 mmHg
The pulse pressure Pp is defined as:
Pp= Ps- Pd
What percentage of standard atmospheric pressure is the pulse pressure of a healthy
adult? - ANS--The pulse pressure in a healthy adult is 120mmHg -75mmHg = 45 mmHg
45mmHg/750mmHg= 6%
How to find work from power generated? - ANS--(Power) x (time in seconds)= joules of
energy
-If you find that the movement of 9L of blood through a brachial artery occurs in 10
minutes, and that correlates to 200 W of power, you multiply 200W x 600 seconds= 120
kJ
Iodine reaction with thiol group - ANS--Leads to the formation of a disulfide and when a
thiol is part of a large molecule, it forms a disulfide linkage
-This is a form of intermolecular covalent bonding
On what amino acid does phosphorylation occur? - ANS-Serine
Why is the velocity of blood flow slower in capillaries than in arteries? - ANS--The total
cross sectional area of capillaries exceeds that of arteries
-The high number of capillaries in the body means that the total cross-sectional area of
these vessels is larger than any other type in the circulatory system. This causes the
blood velocity to decrease
Human rhodopsin is a g protein-coupled receptor found in rod cells in the retina.
Rhodopsin is composed of opsin, a family of seven helix transmembrane proteins and a
covalently attached coenzyme, retinal
The production of a variety of opsins function to do what? - ANS--Enable the detection
of different colors
-The wavelength of light absorbed by a molecule depends on its structure, and so the
production of a variety of structurally related opsins functions to enable the detection of
different colors
Which reaction is catalyzed from protein lysosomal lipase (LipA)? - ANS--Hydrolysis of
triacylglycerides
-The LipA is a lipase, which means it must hydrolyze fatty acids.
What type of bond is formed by glycogen synthase upon release of UDP? - ANS-alpha-
1,4- glycosidic bond
Beta - decay - ANS-radioactive decay of an atomic nucleus that is accompanied by the
emission of a beta particle
, What is a homogenous catalyst - ANS--A catalyst in the same phase as the reactants
-If it cannot separate from the products at the end of a reaction, the products will be
contaminated.
What is a heterogenous catalyst - ANS-A catalyst that is in a different phase from the
reactants
How will the rate of a catalyzed reaction be affected if the solid catalyst is finely ground
before it is added to the reaction mixture? - ANS--The rate will be faster because a
greater surface area of catalyst will be exposed
-Grinding a hetergeneous catalyst increases the amount of catalyst available to the
reaction and therefore increases its rate
How can you determine from the electric potential if a reaction will be spontaneous? -
ANS--If a reaction is spontaneous, than the electric potential (E) will be greater than
zero (positive)
BaCrO4 (s) -> Ba^2+(aq) + CrO4^2-(aq)
This exists in a saturated aqueous solution of BaCrO4. The addition of Na2CrO4 in a
saturated BaCrO4 solution would do what? - ANS--This will cause the equilibrium to
shift to the left
-The dissolution of Na2CrO4 would introduce the common ion, CrO4^2-, which would
reduce the solubility of BaCrO4 due to the common ion effect
Epilepsy may result in motor seizures due to massive synchronous firing of neurons in a
small area of the cerebral cortex (the epileptic focus). The excitation spreads from the
focus, involving an increasingly larger area of the cortex. A drug for the treatment of
epilepsy would be most effective if it caused what changes in epileptic focus? - ANS--An
increase in neuron firing threshold
-A drug that would best treat epilepsy, should reduce the activity of the neurons in the
epileptic focus, which are excitatory neurons based on their effect throughout the cortex
-Increasing the threshold required to generate an action potential would decrease the
chance that individual neurons would fire, thus reducing the overall amount of excitation
that spreads from the epileptic focus throughout the cortex
What are three ways to measure the activity of the Na+ K+ ATPase? - ANS--Measuring
the rate of ATP hydrolysis
-Measuring the rate of ADP production
-Measuring the change in ion concentration within the liposome
Why does measuring the free energy change of the ion transport not determine activity
of Na+ K+ ATPase? - ANS--Free energy is a thermodynamic quantity and is not a
kinetic property. Activity is a kinetic property
