2024 MCAT PRACTICE EXAM
QUESTIONS WITH CORRECT
ANSWERS
Why are triacylglycerols used in the human body for energy storage?
A) They are highly hydrated, and therefore can store lots of energy.
B) They always have short fatty acid chains, for easy access by metabolic
enzymes.
C) The carbon atoms of the fatty acid chains are highly reduced, and
therefore yield more energy upon oxidation.
D) Polysaccharides, which would actually be a better energy storage form,
would dissolve in the body. - CORRECT ANSWERS-C
Triacylglycerols are highly hydrophobic and therefore not highly hydrated
(which would add extra weight from the water of hydration, taking away
from the energy density of these molecules), eliminating choice (A). The
fatty acid chains produce twice as much energy as polysaccharides during
oxidation because they are highly reduced. The fatty acid chains vary in
length and saturation.
Most of the CO2 in the blood travels as HCO3- and H+ ions in the plasma.
Which of the following would a physician most likely find upon examining a
person who has recently had Acute Mountain Sickness (Altitude Sickness)?
A) Increased levels of O2 in the plasma
B) A decreased rate of ventilation
C) An increased red blood cell count
D) An increased white blood cell count - CORRECT ANSWERS-C
Altitude sickness occurs when a person climbs faster than his body can
adjust. One of the ways that the body compensates for the lack of O2 at high
altitude is by releasing erythropoitin, a hormone that increases the RBC
mass after a period ranging from a few days to several weeks.
Chemical extraction is a simple, but powerful, means of isolating a desired
compound, and this technique is used to isolate many pharmacological
agents. A chemist requires that a mixture of two species be separated. In
order to do this, the chemist allows the mixture to separate and extracts the
top, non-polar layer. Based on this information, what is least likely to be true
of the original two species?
, A) The densities of the species are different.
B) The original species rotate plane-polarized light in opposite directions.
C) The bottom layer is hydrophobic.
D) The two species have the same molecular weight. - CORRECT ANSWERS-B
describes the species as enantiomers. If the two species can be separated
through ordinary means, without first changing them chemically, they cannot
be enantiomers! Enantiomers cannot be separated by physical properties
alone.
Ideal gasses are useful for calculations, but perfectly "ideal" gasses do not
exist in the real world. Under what conditions does a real gas differ in
behavior from an ideal gas?
A) increased pressure only
B) increased temperature only
C) increased pressure and decreased temperature
D) only when the molar volume is very large - CORRECT ANSWERS-C
Real gases deviate from the ideal gas law due to elevated pressures and
decreased temperatures. This is because as pressure increases, the
molecules are forced closer together, so intermolecular interactions become
important. When the molecules are far apart, the intermolecular forces are
minimal. As temperature decreases, gas particles move more slowly, so as
they pass each other, the period of time in which they are in close proximity
increases. This allows more opportunities for the molecules to affect one
another. Hence, deviations from ideal conditions result.
Action potentials travel down neural axons that resist the flow of current. In
considering a theoretical circuit, one normally assumes that the wire has no
resistivity. In the real world, however, wire resistivity is an important
consideration. Which of the following is a way to increase resistance?
A) Lengthen the wire
B) Widen the wire
C) Lower the temperature
D) Change from tungsten to copper wire - CORRECT ANSWERS-A
This question tests your knowledge of resistance in wires. An electrical wire's
resistance is directly proportional to its length and inversely proportional to
its cross-sectional area. Think of it as gravel in a pipe—the wider the pipe
and the shorter the pipe, the easier it is for water to go through it.
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