MCAT Practice Questions with Complete
Reliable Solutions
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. -
Answer 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.
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 - Answer 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.
B is incorrect because when a wire's cross-sectional area is increased, its resistivity is decreased.
C is incorrect because lowering temperature decreases resistivity. Think superconductors.
, D is incorrect because tungsten has higher resistivity than copper. Tungsten is used for lightbulb
filaments because of its higher resistivity.
Sexually reproducing species have a selective advantage over asexually reproducing species, because
sexual reproduction:
A) is more energy efficient.
B) creates novel genetic recombinations.
C) decreases the likelihood of mutations.
D) always decreases offspring survival rate. - Answer B
The reason those species that reproduce sexually have a selective advantage is because gene
recombination is a given with every fertilization—two genetically unique nuclei—the sperm nucleus and
the egg nucleus--fuse to form an equally genetically unique zygote. This is the main means of
introducing phenotypic variability into a population.
Pus is primarily composed of phagocytosed bacterial remnants. Which of the following would you
expect to find in a microscopic sample of pus?
A) Red blood cells, white blood cells, and platelets
B) Granulocytes, monocytes, and macrophages
C) Eosinophils, basophils, and neutrophils
D) Collagen, white blood cells, and calcium - Answer B
Phagocytosis plays an important role in both the nonspecific and humoral response to foreign
pathogens. At the level of the skin, macrophages dwell in the connective tissue surrounding the organs
of the body. Neutrophils are recruited to the site of entry and become part of the non-specific response
to invading bacteria, working in combination with monocytes and macrophages to completely
decompose bacteria. The cell-mediated branch of the immune system does not result in pus formation.
Which of the following is true about cholesterol?
A) Cholesterol always increases membrane fluidity in cells.
Reliable Solutions
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. -
Answer 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.
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 - Answer 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.
B is incorrect because when a wire's cross-sectional area is increased, its resistivity is decreased.
C is incorrect because lowering temperature decreases resistivity. Think superconductors.
, D is incorrect because tungsten has higher resistivity than copper. Tungsten is used for lightbulb
filaments because of its higher resistivity.
Sexually reproducing species have a selective advantage over asexually reproducing species, because
sexual reproduction:
A) is more energy efficient.
B) creates novel genetic recombinations.
C) decreases the likelihood of mutations.
D) always decreases offspring survival rate. - Answer B
The reason those species that reproduce sexually have a selective advantage is because gene
recombination is a given with every fertilization—two genetically unique nuclei—the sperm nucleus and
the egg nucleus--fuse to form an equally genetically unique zygote. This is the main means of
introducing phenotypic variability into a population.
Pus is primarily composed of phagocytosed bacterial remnants. Which of the following would you
expect to find in a microscopic sample of pus?
A) Red blood cells, white blood cells, and platelets
B) Granulocytes, monocytes, and macrophages
C) Eosinophils, basophils, and neutrophils
D) Collagen, white blood cells, and calcium - Answer B
Phagocytosis plays an important role in both the nonspecific and humoral response to foreign
pathogens. At the level of the skin, macrophages dwell in the connective tissue surrounding the organs
of the body. Neutrophils are recruited to the site of entry and become part of the non-specific response
to invading bacteria, working in combination with monocytes and macrophages to completely
decompose bacteria. The cell-mediated branch of the immune system does not result in pus formation.
Which of the following is true about cholesterol?
A) Cholesterol always increases membrane fluidity in cells.
