MCAT BIOLOGY PRACTICE QUESTIONS | HIGH-
YIELD REVIEW
1. Compared to untreated WT mice, antibiotic treatment of WT mice is likely to
result in:
A increased plasma butyrate levels.
B decreased body mass.
C increased volume of adipocytes.
D decreased insulin sensitivity in adipocytes.
Passage: "The catabolism of dietary fiber by gut microbiota results in the
production of short chain fatty acids (SCFAs), such as butyrate and acetate,
which are important energy sources for the host. SCFAs also act as signaling
molecules, with the ability to bind and activate G protein-coupled receptors
(GPCRs).": C. Antibiotic treatment means less gut microbiota, thus less SCFA and less activation of GPCRs. This
is similar to the GPCR43-/- condition, which have increased body weight, as indicated in the graph. Increased body
weight, which could mean increased fat and thus increased volume of adipocytes
2. Which event is directly mediated by a ligand-gated ion channel?
A Release of Ca2+ from the sarcoplasmic reticulum of a muscle fiber to initiate
muscle contraction
B Influx of Na+ across the axon membrane of a somatic neuron during action
potential propagation
C Influx of Na+ across the motor end plate resulting in the depolarization of the
muscle fiber membrane
D Re-entry of Ca2+ back into the sarcoplasmic reticulum of a muscle fiber to
end muscle contraction: C because the influx of Na+ across the motor end plate occurs when Na+ ion
channels bind the ligand acetylcholine
3. An inactive tetramer of IN is expected to have approximately what molecular
weight?
A 16 kDa
B 32 kDa
C 64 kDa
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, MCAT BIOLOGY PRACTICE QUESTIONS | HIGH-
YIELD REVIEW
D 128 kDa
Passage: "IN is a 288-residue protein composed of three domains: the N-ter-
minal domain, the catalytic core domain (CCD), and the C-terminal domain.": D
because the passage indicates that an integrase monomer is composed of 288 amino acids, which will have an
approximate molecular weight of 32 kDa (the average molecular weight of an amino acid is 110 Da)
4. The organ in which the holo-RBP complex forms also functions to:
A store bile.
B secrete glucagon.
C produce hydrochloric acid.
D detoxify drugs.
Passage: "In the liver, retinol forms a complex with RBP known as holo-RBP.": D
because according to the passage the holo-RBP complex forms in the liver and one of the function of the liver is drug
detoxification
5. In a species of beetle, red body color is dominant to brown. Two red beetles
are crossed and produce 31 red and 9 brown offspring (F1 generation). If two
red F1 beetles are crossed, what is the probability that both red and brown
beetles will appear in the F2 generation? (Note: Assume Mendelian inheritance
patterns.)
A 4/9
B 1/2
C 2/3
D 3/4: A because given Mendelian inheritance patterns, a 3:1 ratio of F1ottspring means that the original crossed
beetles are both heterozygotes, and the F1ottspring are 25% red (homozygous dominant), 50% red (heterozygous),
and 25% brown (homozygous recessive). If two red F1 beetles are crossed and both red and brown beetles appear in
the F2 generation, the F1 red beetles that were crossed must both be heterozygotes. The probability that, of the red
F1 beetles, both were heterozygous is 2/3 × 2/3, or 4/9 (only red beetles were selected from and 2/3 of the red F1
beetles were heterozygous).
2/6
YIELD REVIEW
1. Compared to untreated WT mice, antibiotic treatment of WT mice is likely to
result in:
A increased plasma butyrate levels.
B decreased body mass.
C increased volume of adipocytes.
D decreased insulin sensitivity in adipocytes.
Passage: "The catabolism of dietary fiber by gut microbiota results in the
production of short chain fatty acids (SCFAs), such as butyrate and acetate,
which are important energy sources for the host. SCFAs also act as signaling
molecules, with the ability to bind and activate G protein-coupled receptors
(GPCRs).": C. Antibiotic treatment means less gut microbiota, thus less SCFA and less activation of GPCRs. This
is similar to the GPCR43-/- condition, which have increased body weight, as indicated in the graph. Increased body
weight, which could mean increased fat and thus increased volume of adipocytes
2. Which event is directly mediated by a ligand-gated ion channel?
A Release of Ca2+ from the sarcoplasmic reticulum of a muscle fiber to initiate
muscle contraction
B Influx of Na+ across the axon membrane of a somatic neuron during action
potential propagation
C Influx of Na+ across the motor end plate resulting in the depolarization of the
muscle fiber membrane
D Re-entry of Ca2+ back into the sarcoplasmic reticulum of a muscle fiber to
end muscle contraction: C because the influx of Na+ across the motor end plate occurs when Na+ ion
channels bind the ligand acetylcholine
3. An inactive tetramer of IN is expected to have approximately what molecular
weight?
A 16 kDa
B 32 kDa
C 64 kDa
1/6
, MCAT BIOLOGY PRACTICE QUESTIONS | HIGH-
YIELD REVIEW
D 128 kDa
Passage: "IN is a 288-residue protein composed of three domains: the N-ter-
minal domain, the catalytic core domain (CCD), and the C-terminal domain.": D
because the passage indicates that an integrase monomer is composed of 288 amino acids, which will have an
approximate molecular weight of 32 kDa (the average molecular weight of an amino acid is 110 Da)
4. The organ in which the holo-RBP complex forms also functions to:
A store bile.
B secrete glucagon.
C produce hydrochloric acid.
D detoxify drugs.
Passage: "In the liver, retinol forms a complex with RBP known as holo-RBP.": D
because according to the passage the holo-RBP complex forms in the liver and one of the function of the liver is drug
detoxification
5. In a species of beetle, red body color is dominant to brown. Two red beetles
are crossed and produce 31 red and 9 brown offspring (F1 generation). If two
red F1 beetles are crossed, what is the probability that both red and brown
beetles will appear in the F2 generation? (Note: Assume Mendelian inheritance
patterns.)
A 4/9
B 1/2
C 2/3
D 3/4: A because given Mendelian inheritance patterns, a 3:1 ratio of F1ottspring means that the original crossed
beetles are both heterozygotes, and the F1ottspring are 25% red (homozygous dominant), 50% red (heterozygous),
and 25% brown (homozygous recessive). If two red F1 beetles are crossed and both red and brown beetles appear in
the F2 generation, the F1 red beetles that were crossed must both be heterozygotes. The probability that, of the red
F1 beetles, both were heterozygous is 2/3 × 2/3, or 4/9 (only red beetles were selected from and 2/3 of the red F1
beetles were heterozygous).
2/6
