MCAT Demo Test Biology Section
The stability of the collagen triple helix depends partly on the repetitive sequence of
✅✅
amino acids which comprise the individual alpha helices. Which of the following amino
acids most likely faces the center of the collagen triple helix? - -Glycine
The most stable structure for the collagen triple helix will likely feature the amino acid
with the least sterically-hindered functional group facing the center of the helix; as such,
glycine, whose functional group is a mere hydrogen atom, will be most likely to face the
center of a stable triple helix
It has been shown that hydroxylation of proline in the presence of ascorbic acid
dramatically increases the stability of the procollagen superstructure that comprises
✅✅
collagen. Which of the following likely contributes most to the added stability that results
from hydroxylation? - -Stereoelectronic effects
✅✅
Based on information in the passage and data presented in Figures 2 and 3, the
absence of ascorbic acid causes which of the following outcomes? - -Decrease in
the rate of pro-collagen secretion.
Once radiolabeled for detection, which of the following amino acids would be LEAST
✅✅
likely to accurately measure the amount of non-procollagen secreted? -
-Hydroxyproline
Hydroxyproline is considered a non-proteinogenic - or, "unnatural" - amino acid in the
sense that it is not typically found in the proteins that comprise the body. In addition to
its absence in the list of twenty-one proteinogenic amino acids (the usual 20 plus
selenocysteine), it may be inferred from the passage that hydroxyproline is created
specifically for the increased stability of collagen.
Which of the following is an example of horizontal gene transfer? - ✅✅-Conjugation
between an Hfr and an F- bacterium.
According to the passage, horizontal gene transfer is a process in which an organism
incorporates genetic material from another organism without being the offspring of that
organism. Conjugation, the passing of genetic material from bacteria to bacteria via a
conjugation bridge, is an example of this.
✅✅
The fact that the Sputnik genome contains both mimivirus and mamavirus genes
supports the conclusion that it participates in a process similar to: - -Transduction
The Sputnik genome containing genes from its mamavirus host is similar to a
bacteriophage viral genome that contains bacterial host genes, as happens in
transduction
✅✅
Which of the following is a viral agent that could be used in the development of phage
therapy? - -T4-like coliphages
Phage therapy is the use of bacteriophage to treat bacterial infections. As described in
the passage, the theory is that the virus will attack the disease-causing bacteria and not
the human host.
, ✅✅
Phage therapy would be a more effective treatment option than antibiotics in each of the
following EXCEPT: - -Meningitis caused by Staphylococcus aureus that are
sensitive to the drug oxacillin.
Phage Therapy would be effective for the following:
Steomyelitis, a bone infection where circulation at the infection site is poor.
Chronic urinary tract infection caused by a biofilm, a complex mixture of microbes that
resist the effects of antibiotics.
Pneumonia caused by penicillin-resistant Streptococcus pneumoniae.
✅✅
Which of the following is true regarding action potentials in cardiac cells? -
-Repolarization in both the pacemaker cells and myocytes is due to the efflux of
potassium.
One analytical tool for determining the amount of iron in blood is to treat the blood with
cyanide ion, which complexes with the Fe2+ in hemoglobin and displaces the porphyrin
to form the hexacyanoferrate(II) complex ion, [Fe(CN)6]4-. Which of the following
✅✅
statements supports the use of this method as a quantitative way of determining the iron
concentration? - -The formation constant (Kf) of the [Fe(CN)6]4- ion is much larger
than that of the Fe2+-hemoglobin complex.
A scientist has a vial of cells that can be grown on plates in the lab. She does a
✅✅
transformation experiment on these cells and isolates the RNA a few days later. Which
of the following is true about the cells under study? - -To extract the RNA, the
researcher would have to break down the cell wall and the plasma membrane.
✅✅
Which of the following is true regarding the function of the right and left ventricles? -
-The right ventricle and left ventricle produce unequal systolic pressures, but have
equal ejection fractions.
The right ventricle only supplies the pulmonary circulation and would not require, nor
have the ability, to produce the pressure needed to supply the systemic circulation, as
the left ventricle does.
A researcher studying the visual cortex attempts to record visually evoked responses
from a single neuron but is not observing any change in the firing rate of action
✅✅
potentials when the stimulus is presented, regardless of how bright it is. What is the
most likely reason for this observation? - -The orientation of the stimulus is not
ideal.
The passage explains that sensory neurons display differing responses depending upon
the stimulus. If the cell being recorded from responds to a light stimulus in one
orientation, but not the other, this could explain the lack of a response
An individual action potential in a model neuron results in 100 sodium ions crossing the
cell membrane. Given that the sodium-potassium pump requires a single molecule of
✅✅
ATP per cycle, how many acetyl-CoA would be required to generate enough energy to
extrude the new sodium in the cell via the pump? - -4
Each acetyl-CoA generates 10 ATP equivalents (3 NADH = 7.5 ATP, 1 FADH2 = 1.5
ATP, and 1 GTP = 1 ATP) and the sodium-potassium pump removes three sodium from
, the cell per cycle at the expense of one ATP. A total of 34 cycles of the pump would be
required to remove the 100 sodium from the cell and this would require 34 ATP. To
ensure we have sufficient ATP, four acetyl-CoA are needed.
✅✅
Compared to a stimulus presented at 45 degrees, which of the following is LEAST likely
to have changed in duration in response to a stimulus at 0 degrees? - -Absolute
Refractory Period
As the firing rate of a neuron increases, the absolute refractory period is least likely to
change as it is a function of the inactivation of the voltage-gated sodium channels.
As the rate of action potentials increases, the time between repolarizations,
depolarizations, and the relative refractory period will decrease.
✅✅
Which of the following conditions would cause a sensory neuron designed to detect
wind to convey the greatest amount of information at its peak firing rate? - -A
windy day generating greater neuronal variability
According to the passage, the peak firing rate for a neuron conveys the greatest amount
of information when there is more neuronal variability. In a neuron designed to detect
wind, a windy day would generate greater variability with an inconsistent background
firing rate.
According to the passage and Figure 1, the enzyme glucose-6-phosphate
✅✅
dehydrogenase (G6PDH) produces NADPH by the oxidation of glucose-6-phosphate.
Which of the following would be true about the regulation of G6PDH? - -It is
allosterically stimulated by NADP+
✅✅
Which of the following describes a potential method of how G6PDH deficiency causes
red blood cell lysis and anemia? - -NADP+ and glutathione can no longer be
reduced, allowing the buildup of free radicals in the RBCs.
The passage explains that G6PDH deficiency leads to decreased production of NADPH
and reduced glutathione. Reduced glutathione is required to remove free radicals and
oxidative agents from causing cell damage and lysis. Decreased levels will lead to
destruction of RBCs and hemolytic anemia
Glycogen is stored by the body via polymerization to form both α-1,6 and α-1,4
✅✅
glycosidic bonds. Which one of the following statements would best provide evidence to
support this structural feature? - -Glucose reacts with Benedict's reagent to form a
red precipitate, whereas glycogen does not react.
✅✅
Which of the following are correctly paired as oxidizing and reducing agents in a
reaction of the PPP or glutathione production (Figure 2)? - -Oxidizing agent:
NADP+; reducing agent: G6P
One can determine a compound is reduced in a reaction by the gain of electrons or
bonds to hydrogen. G6P reduced NADP+ into NADPH and conversely, NADP+ oxidizes
G6P into 6GP.
✅✅
Which of the following statements is true regarding the pentose phosphate pathway? -
-The PPP does not directly utilize or produce any molecules of ATP.
The stability of the collagen triple helix depends partly on the repetitive sequence of
✅✅
amino acids which comprise the individual alpha helices. Which of the following amino
acids most likely faces the center of the collagen triple helix? - -Glycine
The most stable structure for the collagen triple helix will likely feature the amino acid
with the least sterically-hindered functional group facing the center of the helix; as such,
glycine, whose functional group is a mere hydrogen atom, will be most likely to face the
center of a stable triple helix
It has been shown that hydroxylation of proline in the presence of ascorbic acid
dramatically increases the stability of the procollagen superstructure that comprises
✅✅
collagen. Which of the following likely contributes most to the added stability that results
from hydroxylation? - -Stereoelectronic effects
✅✅
Based on information in the passage and data presented in Figures 2 and 3, the
absence of ascorbic acid causes which of the following outcomes? - -Decrease in
the rate of pro-collagen secretion.
Once radiolabeled for detection, which of the following amino acids would be LEAST
✅✅
likely to accurately measure the amount of non-procollagen secreted? -
-Hydroxyproline
Hydroxyproline is considered a non-proteinogenic - or, "unnatural" - amino acid in the
sense that it is not typically found in the proteins that comprise the body. In addition to
its absence in the list of twenty-one proteinogenic amino acids (the usual 20 plus
selenocysteine), it may be inferred from the passage that hydroxyproline is created
specifically for the increased stability of collagen.
Which of the following is an example of horizontal gene transfer? - ✅✅-Conjugation
between an Hfr and an F- bacterium.
According to the passage, horizontal gene transfer is a process in which an organism
incorporates genetic material from another organism without being the offspring of that
organism. Conjugation, the passing of genetic material from bacteria to bacteria via a
conjugation bridge, is an example of this.
✅✅
The fact that the Sputnik genome contains both mimivirus and mamavirus genes
supports the conclusion that it participates in a process similar to: - -Transduction
The Sputnik genome containing genes from its mamavirus host is similar to a
bacteriophage viral genome that contains bacterial host genes, as happens in
transduction
✅✅
Which of the following is a viral agent that could be used in the development of phage
therapy? - -T4-like coliphages
Phage therapy is the use of bacteriophage to treat bacterial infections. As described in
the passage, the theory is that the virus will attack the disease-causing bacteria and not
the human host.
, ✅✅
Phage therapy would be a more effective treatment option than antibiotics in each of the
following EXCEPT: - -Meningitis caused by Staphylococcus aureus that are
sensitive to the drug oxacillin.
Phage Therapy would be effective for the following:
Steomyelitis, a bone infection where circulation at the infection site is poor.
Chronic urinary tract infection caused by a biofilm, a complex mixture of microbes that
resist the effects of antibiotics.
Pneumonia caused by penicillin-resistant Streptococcus pneumoniae.
✅✅
Which of the following is true regarding action potentials in cardiac cells? -
-Repolarization in both the pacemaker cells and myocytes is due to the efflux of
potassium.
One analytical tool for determining the amount of iron in blood is to treat the blood with
cyanide ion, which complexes with the Fe2+ in hemoglobin and displaces the porphyrin
to form the hexacyanoferrate(II) complex ion, [Fe(CN)6]4-. Which of the following
✅✅
statements supports the use of this method as a quantitative way of determining the iron
concentration? - -The formation constant (Kf) of the [Fe(CN)6]4- ion is much larger
than that of the Fe2+-hemoglobin complex.
A scientist has a vial of cells that can be grown on plates in the lab. She does a
✅✅
transformation experiment on these cells and isolates the RNA a few days later. Which
of the following is true about the cells under study? - -To extract the RNA, the
researcher would have to break down the cell wall and the plasma membrane.
✅✅
Which of the following is true regarding the function of the right and left ventricles? -
-The right ventricle and left ventricle produce unequal systolic pressures, but have
equal ejection fractions.
The right ventricle only supplies the pulmonary circulation and would not require, nor
have the ability, to produce the pressure needed to supply the systemic circulation, as
the left ventricle does.
A researcher studying the visual cortex attempts to record visually evoked responses
from a single neuron but is not observing any change in the firing rate of action
✅✅
potentials when the stimulus is presented, regardless of how bright it is. What is the
most likely reason for this observation? - -The orientation of the stimulus is not
ideal.
The passage explains that sensory neurons display differing responses depending upon
the stimulus. If the cell being recorded from responds to a light stimulus in one
orientation, but not the other, this could explain the lack of a response
An individual action potential in a model neuron results in 100 sodium ions crossing the
cell membrane. Given that the sodium-potassium pump requires a single molecule of
✅✅
ATP per cycle, how many acetyl-CoA would be required to generate enough energy to
extrude the new sodium in the cell via the pump? - -4
Each acetyl-CoA generates 10 ATP equivalents (3 NADH = 7.5 ATP, 1 FADH2 = 1.5
ATP, and 1 GTP = 1 ATP) and the sodium-potassium pump removes three sodium from
, the cell per cycle at the expense of one ATP. A total of 34 cycles of the pump would be
required to remove the 100 sodium from the cell and this would require 34 ATP. To
ensure we have sufficient ATP, four acetyl-CoA are needed.
✅✅
Compared to a stimulus presented at 45 degrees, which of the following is LEAST likely
to have changed in duration in response to a stimulus at 0 degrees? - -Absolute
Refractory Period
As the firing rate of a neuron increases, the absolute refractory period is least likely to
change as it is a function of the inactivation of the voltage-gated sodium channels.
As the rate of action potentials increases, the time between repolarizations,
depolarizations, and the relative refractory period will decrease.
✅✅
Which of the following conditions would cause a sensory neuron designed to detect
wind to convey the greatest amount of information at its peak firing rate? - -A
windy day generating greater neuronal variability
According to the passage, the peak firing rate for a neuron conveys the greatest amount
of information when there is more neuronal variability. In a neuron designed to detect
wind, a windy day would generate greater variability with an inconsistent background
firing rate.
According to the passage and Figure 1, the enzyme glucose-6-phosphate
✅✅
dehydrogenase (G6PDH) produces NADPH by the oxidation of glucose-6-phosphate.
Which of the following would be true about the regulation of G6PDH? - -It is
allosterically stimulated by NADP+
✅✅
Which of the following describes a potential method of how G6PDH deficiency causes
red blood cell lysis and anemia? - -NADP+ and glutathione can no longer be
reduced, allowing the buildup of free radicals in the RBCs.
The passage explains that G6PDH deficiency leads to decreased production of NADPH
and reduced glutathione. Reduced glutathione is required to remove free radicals and
oxidative agents from causing cell damage and lysis. Decreased levels will lead to
destruction of RBCs and hemolytic anemia
Glycogen is stored by the body via polymerization to form both α-1,6 and α-1,4
✅✅
glycosidic bonds. Which one of the following statements would best provide evidence to
support this structural feature? - -Glucose reacts with Benedict's reagent to form a
red precipitate, whereas glycogen does not react.
✅✅
Which of the following are correctly paired as oxidizing and reducing agents in a
reaction of the PPP or glutathione production (Figure 2)? - -Oxidizing agent:
NADP+; reducing agent: G6P
One can determine a compound is reduced in a reaction by the gain of electrons or
bonds to hydrogen. G6P reduced NADP+ into NADPH and conversely, NADP+ oxidizes
G6P into 6GP.
✅✅
Which of the following statements is true regarding the pentose phosphate pathway? -
-The PPP does not directly utilize or produce any molecules of ATP.
