MCAT Section Bank: Biology & Biochemistry, AAMC Bi
MCAT Section Bank: Biology & Biochemistry, AAMC Bi
Exam (elaborations)
MCAT Section Bank: Biology & Biochemistry, AAMC Biological and Biochemical Foundations of Living Systems || A Verified A+ Pass.
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MCAT Section Bank: Biology & Biochemistry, AAMC Bi
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MCAT Section Bank: Biology & Biochemistry, AAMC Bi
phosphatase correct answers enzyme that removes a phosphate group from its substrate
According to the information in the passage, which statement best describes the function of the MR in response to stimulation of the sympathetic nervous system? The MR:
"Blood flow to the brain is regulated b...
MCAT Section Bank: Biology & Biochemistry, AAMC
Biological and Biochemical Foundations of Living Systems ||
A Verified A+ Pass.
phosphatase correct answers enzyme that removes a phosphate group from its substrate
According to the information in the passage, which statement best describes the function of the
MR in response to stimulation of the sympathetic nervous system? The MR:
"Blood flow to the brain is regulated by changes in arterial vessel diameter in response to
intravascular pressure, a process called the myogenic response (MR). The MR allows cerebral
resistance vessels to achieve a state of partial constriction, from which they can dilate or further
constrict to alter blood flow."
A) equalizes blood pressure in cerebral resistance arteries and the aorta.
B) moderates blood flow to the brain under high pressure.
C) enables cerebral resistance arteries to locally vasodilate.
D) redirects blood circulating in the brain to organs in the abdominal cavity. correct answers B)
moderates blood flow to the brain under high pressure.
The answer to this question is B because the MR is a local response in resistance vessels that
would slow blood flow to the brain to reduce the chance of tissue damage from high blood
pressure resulting from activation of the sympathetic nervous system.
The polymerization of which structural component was analyzed in the experiment described in
the passage? (Actin polymerization)
A) Microtubules
B) Microfilaments
C) Intermediate filaments
D) Thick filaments correct answers B) Microfilaments
The answer to this question is B because microfilaments are composed of actin.
Which amino acid is LEAST likely found in one of the transmembrane domains of GPCR43?
A) Asp
B) Gly
C) Trp
D) Phe correct answers A) Asp
The answer to this question is A because aspartate (Asp) has a negatively charged R group and is
very hydrophilic.
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. correct answers C) increased volume of
adipocytes
The answer to this question is C because if SCFA producing microbes were removed by
antibiotic treatment, then GPCR43 would not be activated to reduce glucose uptake into
adipocytes.
Which amino acid contains an unbranched alkyl side chain?
A) Ala
B) Ile
C) Leu
D) Val correct answers A) Ala
The answer to this item is A since alanine contains a methyl side chain, which is not considered a
branched alkane.
The stereochemical designators α and β distinguish between:
A) enantiomers at an epimeric carbon atom.
B) enantiomers at an anomeric carbon atom.
C) epimers at an anomeric carbon atom.
D) epimers at a non-anomeric carbon atom. correct answers C) epimers at an anomeric carbon
atom.
The answer to this item is C since the D versus L designation distinguishes between molecules
with multiple chiral centers, but differ only in the configuration of the site known as the
anomeric carbon atom.
Which ideal solution exhibits the greatest osmotic pressure?
A) 0.1 M MgCl2
B) 0.2 M NaCl
C) 0.2 M CaCl2
D) 0.5 M Glucose correct answers C) 0.2 M CaCl2
The answer to this question is C because the solution listed has the greatest concentration of
solute particles. CaCl2 dissociates into three ions, making the solution listed 0.6 M in solute
particles.
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 correct answers C) Influx of Na+ across the motor end plate resulting in the
depolarization of the muscle fiber membrane
The answer to this question is C because the influx of Na+ across the motor end plate occurs
when Na+ ion channels bind the ligand acetylcholine.
Southern blot correct answers A Southern blot uses a restriction digest to differentiate between
mutant and wild-type alleles. In order for a Southern blot to be useful, the mutation should either
create or eliminate a restriction site, most of which are palindromes and 4 to 6 base pairs long.
The mutation shown in this option is the only one that disrupts a palindromic sequence,
AAGCTT. This sequence is the recognition sequence for HindIII.
What bond is cleaved by IN during the first reaction of integration?
"Upon binding, IN catalyzes cleavage of a GT dinucleotide from each 3 PRIME vDNA
terminus"
A) P-C
B) P-P
C) P-H
D) P-O correct answers D) P-O
The answer to this question is D because in the first reaction of integration, integrase cleaves a
dinucleotide from the 3' end of a strand of viral DNA.
A vDNA sequence encoding a protein is inserted into a host genome by IN. The protein is
translated from the hypothetical mRNA sequence shown.
5'-GGCAACUGACUA-3'
Based on the passage, the segment of the original viral genome that encoded this protein had
what nucleotide sequence? correct answers 5'-GGCAACUGACUA-3'
The answer to this question is A because according to the passage, viral DNA integrated into a
host cell genome by integrase would originate from a retrovirus. mRNA transcribed from
retroviral DNA is either used to synthesize viral proteins, or used as the RNA genome for
progeny viruses. Thus, the sequence of the nucleotide in the original viral genome will be the
same as that of the transcribed mRNA.
Which experiment would best provide data to support the mechanism by which an ODN inhibits
IN activity?
, "ODNs are competitive inhibitors of vDNA for binding to IN."
A) Keep IN concentration constant and measure the initial velocity of the reaction at increasing
vDNA concentrations in the presence and absence of the ODN.
B) Keep vDNA concentration constant and measure the initial velocity of the reaction at
increasing concentrations of IN in the presence and absence of the ODN.
C) Keep ODN and IN concentration constant and measure initial velocity of the reaction at
increasing concentrations of vDNA.
D) Keep IN and vDNA concentrations constant and measure initial velocity of the reaction at
increasing concentrations the ODN. correct answers A) Keep IN concentration constant and
measure the initial velocity of the reaction at increasing vDNA concentrations in the presence
and absence of the ODN.
Competitive inhibition can be determined through rate experiments by applying the principles of
the Michaelis-Menten equation. By keeping enzyme concentration constant, varying substrate
concentration, and either including or excluding the inhibitor, the effect of the inhibitor on the
Vmax and apparent Km of the reaction can be determined. A competitive inhibitor will increase
the apparent Km and not affect the Vmax.
Which amino acid substitution for the conserved residue at position 64 is LEAST likely to affect
the enzymatic function of IN?
Highly conserved residue = D64
A) Asparagine
B) Glutamate
C) Lysine
D) Valine correct answers B) Glutamate
The answer to this question is B because the conserved residue at position 64 in integrase is
aspartate, which has a negatively charged side chain. Substitution with glutamate, which also has
a negatively charged side chain, is least likely to affect integrase function.
An inactive tetramer of IN is expected to have approximately what molecular weight?
"IN is a 288-residue protein composed of three domains"
A) 16 kDa
B) 32 kDa
C) 64 kDa
D) 128 kDa correct answers D) 128 kDa
The answer to this question is 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). Thus, a tetramer will have an
approximate molecular weight of 128 kDa.
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