MCAT Question of the Day questions and
answers
Which layer of the epidermis is characterized by a low rate of mitosis and a high
concentration of keratin?
A. Stratum basale
B. Stratum spinosum
C. Stratum corneum
D. Stratum lucidum - Correct Answer: C. Stratum corneum
If a layer of epidermis has a low rate of mitosis, this indicates that the cells in this
layer are not dividing very frequently. Likewise the presence of keratin, signals
that the layer of epidermis must have a waterproofing function. The stratum
basale is the most mitotic layer and is the bottom layer of the epidermis. As the
cells are produced in the stratum basale, older cells are pushed up to the stratum
spinosum, which is also high in mitotic activity. Keratin dominates in the stratum
corneum, which is the most superficial layer of the epidermis, characterized by
dead skin cells that are no longer undergoing mitosis. Therefore, the correct
answer is [C].
Pulmonary alveolus (plural form:alveoli) is an integral component of the
mammalian respiratory system, which of the following characteristics describes
this component?
,MCAT Question of the Day questions and
answers
a) Actively transports O2 into the bloodstream
b) Allows for gas diffusion to occur and the exchange of CO2 for O2 in the
bloodstream
c) Hollow cavities at the end of the respiratory tree
d) B and C - The correct answer is D.
Alveoli are found in the parenchyma of the lungs at the terminal end of the
respiratory tree. Alveoli in the lungs of mammals are the key structure in
facilitating the exchange of CO2 and O2 across the alveolar membrane by
pumping CO2 rich blood from the body into the oxygen rich alveoli and allowing
the exchange to occur through diffusion, not active transport.
A blood cell is placed into a salt-water mixture (70% salt). What is likely to result if
the red blood cell's membrane is permeable to water?
A. The cell will burst
B. The cell will shrivel
C. The cell will degrade
D. The cell will shrivel, then expand - Correct Answer: B.
,MCAT Question of the Day questions and
answers
The cell will shrivel. For cells with a selectively permeable membrane, water will
move from higher water concentrations to lower water concentrations. In this
problem, the salt is too large to cross the membrane, so the salt concentration will
remain the same. Since red blood cells have more water than the salt-water
mixture, the water in the cell would leave to try to make the two environments
isotonic. If water leaves the cell, the cell will eventually shrink.
Which reagent would you choose to convert hexan-1-ol to hexanal?
A. PCC/CH2Cl2
B. DIBAL/diethyl ether
C. KMnO4/aqueous H2SO4/acetone.
D. K2Cr2O7/aqueous H2SO4/acetone. - Correct Answer: A. PCC/CH2Cl2.
Pyridinium chlorochromate (PCC) is a mild oxidant, which converts primary and
secondary alcohols to aldehydes and ketones respectively. KMnO4 and K2Cr2O7
are harsher oxidants, and would further oxidize primary alcohols to the
corresponding carboxylic acids. Di-isobutylaluminum hydride (DIBAL) is a reducing
agents.
, MCAT Question of the Day questions and
answers
A construction worker uses a crane to vertically lift an object weighing 2000 N to
the top of a platform at a constant rate. If it takes 30 seconds to lift the object 150
meters, what is the rate of energy consumed by the motor in the crane?
A. 5.0 kW
B. 8.0 kW
C. 10.0 kW
D. 12.0 kW - Correct Answer: C. 10 kW.
We can use the equation Power = Force*velocity to solve this problem. The object
moves 150 meters in 30 seconds, so the velocity must be (150m/30s) = 5 m/s.
Plugging this back into the original equation of P = Fv, then P = (2000 N)(5 m/s) =
10 kW.
During the fusion stage in human fertilization, which of the following would you
NOT expect to occur?
A. A fusion of chromosomes from the sperm and oocyte.
B. Oocyte transfers itself into a mature ovum.
answers
Which layer of the epidermis is characterized by a low rate of mitosis and a high
concentration of keratin?
A. Stratum basale
B. Stratum spinosum
C. Stratum corneum
D. Stratum lucidum - Correct Answer: C. Stratum corneum
If a layer of epidermis has a low rate of mitosis, this indicates that the cells in this
layer are not dividing very frequently. Likewise the presence of keratin, signals
that the layer of epidermis must have a waterproofing function. The stratum
basale is the most mitotic layer and is the bottom layer of the epidermis. As the
cells are produced in the stratum basale, older cells are pushed up to the stratum
spinosum, which is also high in mitotic activity. Keratin dominates in the stratum
corneum, which is the most superficial layer of the epidermis, characterized by
dead skin cells that are no longer undergoing mitosis. Therefore, the correct
answer is [C].
Pulmonary alveolus (plural form:alveoli) is an integral component of the
mammalian respiratory system, which of the following characteristics describes
this component?
,MCAT Question of the Day questions and
answers
a) Actively transports O2 into the bloodstream
b) Allows for gas diffusion to occur and the exchange of CO2 for O2 in the
bloodstream
c) Hollow cavities at the end of the respiratory tree
d) B and C - The correct answer is D.
Alveoli are found in the parenchyma of the lungs at the terminal end of the
respiratory tree. Alveoli in the lungs of mammals are the key structure in
facilitating the exchange of CO2 and O2 across the alveolar membrane by
pumping CO2 rich blood from the body into the oxygen rich alveoli and allowing
the exchange to occur through diffusion, not active transport.
A blood cell is placed into a salt-water mixture (70% salt). What is likely to result if
the red blood cell's membrane is permeable to water?
A. The cell will burst
B. The cell will shrivel
C. The cell will degrade
D. The cell will shrivel, then expand - Correct Answer: B.
,MCAT Question of the Day questions and
answers
The cell will shrivel. For cells with a selectively permeable membrane, water will
move from higher water concentrations to lower water concentrations. In this
problem, the salt is too large to cross the membrane, so the salt concentration will
remain the same. Since red blood cells have more water than the salt-water
mixture, the water in the cell would leave to try to make the two environments
isotonic. If water leaves the cell, the cell will eventually shrink.
Which reagent would you choose to convert hexan-1-ol to hexanal?
A. PCC/CH2Cl2
B. DIBAL/diethyl ether
C. KMnO4/aqueous H2SO4/acetone.
D. K2Cr2O7/aqueous H2SO4/acetone. - Correct Answer: A. PCC/CH2Cl2.
Pyridinium chlorochromate (PCC) is a mild oxidant, which converts primary and
secondary alcohols to aldehydes and ketones respectively. KMnO4 and K2Cr2O7
are harsher oxidants, and would further oxidize primary alcohols to the
corresponding carboxylic acids. Di-isobutylaluminum hydride (DIBAL) is a reducing
agents.
, MCAT Question of the Day questions and
answers
A construction worker uses a crane to vertically lift an object weighing 2000 N to
the top of a platform at a constant rate. If it takes 30 seconds to lift the object 150
meters, what is the rate of energy consumed by the motor in the crane?
A. 5.0 kW
B. 8.0 kW
C. 10.0 kW
D. 12.0 kW - Correct Answer: C. 10 kW.
We can use the equation Power = Force*velocity to solve this problem. The object
moves 150 meters in 30 seconds, so the velocity must be (150m/30s) = 5 m/s.
Plugging this back into the original equation of P = Fv, then P = (2000 N)(5 m/s) =
10 kW.
During the fusion stage in human fertilization, which of the following would you
NOT expect to occur?
A. A fusion of chromosomes from the sperm and oocyte.
B. Oocyte transfers itself into a mature ovum.
