AAMC Biological and
Biochemical Foundations of
Living Systems with correct
answers 2025/2026
A certain bacterium was cultured for several generations in medium containing 15N,
transferred to medium containing 14N, and allowed to complete two rounds of cell
division. Given that the bacterium's genome mass is 5.4 fg when grown in 14N media
and 5.5 fg when grown in 15N medium, individual bacteria with which of the following
genome masses would most likely be isolated from this culture?
A.5.4 fg only
B.5.4 fg and 5.45 fg
C.5.4 fg and 5.5 fg
D.5.45 fg only - correct answerThe answer to this question is B because DNA
replication is semi-conservative. Therefore, after the first round of cell division the
genome mass in each bacterium will be 5.45 fg (one DNA strand will contain 15N and
the other strand 14N). Following the second round of cell division, half of the bacteria
will have a genome mass of 5.4 fg (14N exclusively) and the other half a mass genome
of 5.45 fg (14N in one DNA strand and 15N in the other).
A fatty acid is comprised of a long hydrocarbon tail and a head consisting of:
a hydroxyl group.
,B.a carboxyl group.
C.a phosphate group.
D.an amino group. - correct answerThe answer to this question is B because fatty acids
contain a carboxylic acid head group and a hydrocarbon tail.
A homodimeric protein was found to migrate through SDS polyacrylamide gel
electrophoresis (SDS-PAGE) with a mobility that matched that of a 45-kDa standard.
What change in the experiment would increase the chances of observing the mobility
expected for the 22.5-kDa monomer?
A.Increasing the gel running time
B.Adding a reducing agent
C.Using a higher voltage
D.Removing the SDS - correct answerThe answer to this question is B because adding
a reducing agent would eliminate any disulfide bridges and allow the monomers to run
separately-thus leading to a migration expected for the 22.5-kDa protein.
A lower-than-normal blood pressure will cause which of the following effects on the rate
of plasma clearance of Substance A?
A. An increase, because the concentration of Substance A in the urine will increase
B. An increase, because the ADH levels will be very low
C. A decrease, because the decreased rate of urine output will allow more reabsorption
by the kidney
D. A decrease, because ADH levels will be very high - correct answerLow blood
pressure could have an effect on ADH levels (as suggested in answer choices B and
D), which could, in turn, affect the amount of substance A in the urine, but there is not
enough information in the passage to decide if such an effect exists and, if it does,
whether its effect would overcome the certain affect of lowering the blood pressure. The
best answer is answer choice C: that low blood pressure decreases the glomerular
,filtration rate, allowing more time for reabsorption and decreasing the amount of
substance A in the urine.
Blood pressure is the source of the energy that forces fluid into the capsular space. If
the heart stopped and the blood in the glomerular capillaries had no hydrostatic
pressure, fluid in the space around the glomerulus would flow back into the capillary
bloodstream.
A novel compound was developed which occupies the site on STx where GPP130 binds
the toxin. A drug with which value of Kd for binding to STx is most effective?
A.0.25 mM
B.2.5 mM
C.25 mM
D.250 mM - correct answerThe answer to this question is A because in order to be a
feasible option, the Kd for the compound and STx must be below the Kd of STx and
GPP130. The lower the Kd of the drug, the more effective it will be at inhibiting the
interaction between STx and GPP130 because it will bind to STx instead of STx binding
to GPP130.
A prion is best described as an infectious:
A.prokaryote.
B.transposon.
C.protein.
D.virus. - correct answerThe answer to this question is C because a prion is an
abnormally folded protein that induces a normally folded version of the protein to also
adopt the abnormal structure, which is often deleterious.
, A scientist claimed that hemophilia is caused by a functional deficiency in Factor VIII.
The evidence in the passage that would best support this claim is that Factor VIII is:
A.a soluble blood protein.
B.produced by a gene on the X chromosome.
C.able to relieve hemophilia symptoms.
D.encoded by a gene that contains introns. - correct answerhe answer to this question
is C because the passage states that the symptoms of hemophilia can be at least
partially alleviated by administration of functional Factor VIII, which would help counter
functional deficiencies in Factor VIII in the affected individual. All of the other options
can be characteristics of both functional and nonfunctional proteins and, thus, do not
provide the best support for the claim.
A separate group of scientists repeated the amino acid transport experiments described
in the passage. All protocols were performed as outlined in the initial study with one
major exception: D-alanine was used as the primary amino acid substrate. What effect
will this change have on the synthesis of new proteins in the animals studied? Protein
synthesis will:
A.increase two-fold.
B.not change.
C.decrease by one-half.
D.be inhibited. - correct answerThe answer to this question is D because only L isomers
are used to form proteins during ribosomal protein synthesis.
ADP-ribosylation factor I (Arf1) plays an essential role in vesicle formation and is
responsible for the recruitment of cytosolic coat protein complexes (COPs) and
subsequent retrograde transport from the Golgi apparatus.
Proteins that are encapsulated in Arf1-COP derived vesicles are bound for the:
Biochemical Foundations of
Living Systems with correct
answers 2025/2026
A certain bacterium was cultured for several generations in medium containing 15N,
transferred to medium containing 14N, and allowed to complete two rounds of cell
division. Given that the bacterium's genome mass is 5.4 fg when grown in 14N media
and 5.5 fg when grown in 15N medium, individual bacteria with which of the following
genome masses would most likely be isolated from this culture?
A.5.4 fg only
B.5.4 fg and 5.45 fg
C.5.4 fg and 5.5 fg
D.5.45 fg only - correct answerThe answer to this question is B because DNA
replication is semi-conservative. Therefore, after the first round of cell division the
genome mass in each bacterium will be 5.45 fg (one DNA strand will contain 15N and
the other strand 14N). Following the second round of cell division, half of the bacteria
will have a genome mass of 5.4 fg (14N exclusively) and the other half a mass genome
of 5.45 fg (14N in one DNA strand and 15N in the other).
A fatty acid is comprised of a long hydrocarbon tail and a head consisting of:
a hydroxyl group.
,B.a carboxyl group.
C.a phosphate group.
D.an amino group. - correct answerThe answer to this question is B because fatty acids
contain a carboxylic acid head group and a hydrocarbon tail.
A homodimeric protein was found to migrate through SDS polyacrylamide gel
electrophoresis (SDS-PAGE) with a mobility that matched that of a 45-kDa standard.
What change in the experiment would increase the chances of observing the mobility
expected for the 22.5-kDa monomer?
A.Increasing the gel running time
B.Adding a reducing agent
C.Using a higher voltage
D.Removing the SDS - correct answerThe answer to this question is B because adding
a reducing agent would eliminate any disulfide bridges and allow the monomers to run
separately-thus leading to a migration expected for the 22.5-kDa protein.
A lower-than-normal blood pressure will cause which of the following effects on the rate
of plasma clearance of Substance A?
A. An increase, because the concentration of Substance A in the urine will increase
B. An increase, because the ADH levels will be very low
C. A decrease, because the decreased rate of urine output will allow more reabsorption
by the kidney
D. A decrease, because ADH levels will be very high - correct answerLow blood
pressure could have an effect on ADH levels (as suggested in answer choices B and
D), which could, in turn, affect the amount of substance A in the urine, but there is not
enough information in the passage to decide if such an effect exists and, if it does,
whether its effect would overcome the certain affect of lowering the blood pressure. The
best answer is answer choice C: that low blood pressure decreases the glomerular
,filtration rate, allowing more time for reabsorption and decreasing the amount of
substance A in the urine.
Blood pressure is the source of the energy that forces fluid into the capsular space. If
the heart stopped and the blood in the glomerular capillaries had no hydrostatic
pressure, fluid in the space around the glomerulus would flow back into the capillary
bloodstream.
A novel compound was developed which occupies the site on STx where GPP130 binds
the toxin. A drug with which value of Kd for binding to STx is most effective?
A.0.25 mM
B.2.5 mM
C.25 mM
D.250 mM - correct answerThe answer to this question is A because in order to be a
feasible option, the Kd for the compound and STx must be below the Kd of STx and
GPP130. The lower the Kd of the drug, the more effective it will be at inhibiting the
interaction between STx and GPP130 because it will bind to STx instead of STx binding
to GPP130.
A prion is best described as an infectious:
A.prokaryote.
B.transposon.
C.protein.
D.virus. - correct answerThe answer to this question is C because a prion is an
abnormally folded protein that induces a normally folded version of the protein to also
adopt the abnormal structure, which is often deleterious.
, A scientist claimed that hemophilia is caused by a functional deficiency in Factor VIII.
The evidence in the passage that would best support this claim is that Factor VIII is:
A.a soluble blood protein.
B.produced by a gene on the X chromosome.
C.able to relieve hemophilia symptoms.
D.encoded by a gene that contains introns. - correct answerhe answer to this question
is C because the passage states that the symptoms of hemophilia can be at least
partially alleviated by administration of functional Factor VIII, which would help counter
functional deficiencies in Factor VIII in the affected individual. All of the other options
can be characteristics of both functional and nonfunctional proteins and, thus, do not
provide the best support for the claim.
A separate group of scientists repeated the amino acid transport experiments described
in the passage. All protocols were performed as outlined in the initial study with one
major exception: D-alanine was used as the primary amino acid substrate. What effect
will this change have on the synthesis of new proteins in the animals studied? Protein
synthesis will:
A.increase two-fold.
B.not change.
C.decrease by one-half.
D.be inhibited. - correct answerThe answer to this question is D because only L isomers
are used to form proteins during ribosomal protein synthesis.
ADP-ribosylation factor I (Arf1) plays an essential role in vesicle formation and is
responsible for the recruitment of cytosolic coat protein complexes (COPs) and
subsequent retrograde transport from the Golgi apparatus.
Proteins that are encapsulated in Arf1-COP derived vesicles are bound for the:
