UNM SOM MCAT EXAM |QUESTIONS AND
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ANSWERS|LATEST 2025-2026
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The process by which the autonomic nervous system activates HCN channels is best
described by which of the following?
A. Sympathetic stimulation causes acetylcholine release, thereby activating cardiac tyrosine
kinase receptors, resulting in elevated cAMP levels.
B. Parasympathetic stimulation causes acetylcholine release, thereby activating tyrosine
kinase receptors, resulting in elevated cAMP levels.
C. Sympathetic stimulation causes epinephrine release, thereby activating G-protein coupled
receptors, resulting in elevated cAMP levels.
D. Parasympathetic stimulation causes epinephrine release, thereby activating G-protein
coupled receptors, resulting in elevated cAMP levels. - ANSWER C. The passage states
that cAMP binding opens and activates HCN channels, causing increased depolarization of
the heart, and therefore should increase heart rate. The sympathetic nervous system is
responsible for increasing heart rate, while the parasympathetic nervous system is
responsible for slowing it (choices B and D are wrong). Activation of the sympathetic nervous
system results in the release of norepinephrine from post-ganglionic neurons and
epinephrine from the adrenal medulla (choice A is wrong). Epinephrine acts on G-protein
coupled receptors, which activate adenylate cyclase to convert ATP to cAMP (choice C is
correct).
Modern civilization's insulation from natural phenomena has, of course, altered our
relationship to the weather substantially. The material successes of two centuries of applied
science have thoroughly dislodged the old deities as active presences in earthly affairs, and
our apparent control over nature has emptied it much of its metaphysical significance. Like
the wilds that once confronted a traveler just outside the city's gates, the weather has been
suburbanized and Disneyfied, its inclemencies signifying, for the most part, little more than
inconvenience. In the intensely humanized environment where much of the First World
lives—an environment so man-made as to often be called "dehumanizing"—we rarely pay
attention to the sky as a scene of drama and omen; it would seem that for many people the
TV weatherman has equal, if not more, phenomenal reality. And while we might find
vestiges of an earlier relationship in - ANSWER B. This is an Analogy question.
1
,A: No. In the last sentence of the passage, the author says, "The tragic irony of our
egocentric disenchantment of the world is this: we may one day come to 'own the weather'
only to find that the weather has turned as ugly and as rapacious as we." The right answer
for this question must therefore involve a scenario where someone assumes nature can be
dominated only to have it respond in a seemingly vengeful way. In this scenario, the
gardener exhibits neglect, thinking that nature will take care of itself; there is no attempt to
control or manipulate nature.
B: Yes. At the end of the passage, the author says, "The tragic irony of our egocentric
disenchantment of the world is this: we may one day come to 'own the weather' only to find
that the weather has turned as ugly and as rapacious as we." This extends the idea
introduced in the previous paragraph that by trying to control the weather, we may
unintentionally bring about catastrophic events. The right answer for this question must
therefore involve a scenario where someone assumes nature can be dominated only to have
it respond in a seemingly vengeful way. This answer choice involves the human attempt to
dominate nature; by introducing a foreign species of plant, the corporation is attempting to
manipulate nature for humans' (or at least the corporation's) benefit. Then, nature responds
back by negatively affecting humans' lives (or at least subverting the corporation's goals).
This is a good fit with the argument made in the passage.
C: No. While this answer contains the essential element of nature turning ugly in the end, it
lacks the element of attempted human dominance of nature. There is no information
provided in this choice about an attempt to subdue or control the dog.
D: No. This answer choice does not contain the "ugly" res
Which of the following is true of the differences between the forces exerted on a given
object by water and mercury? (ρ = 13500 kg/m3)
A. The maximum buoyant force is greater in mercury, and the maximum surface tension
force is greater in mercury.
B. The maximum buoyant force is greater in mercury, but the maximum surface tension
force is greater in water.
C. The maximum buoyant force is equal in both, but the maximum surface tension force is
greater in mercury.
D. The maximum buoyant force is equal in both, but the maximum surface tension force is
greater in water. - ANSWER A.
The coefficient of surface tension is greater in mercury, so eliminate choices B and D; the
maximum force of surface tension is greater in mercury. The force of buoyancy is given by Fb
= ρfVsubg, and g should not change. The maximum value of V should not either; the object
2
,can always be fully submerged, so the maximum value of V is just the total volume of the
object. (Note that the question does not ask about the value at any equilibrium, so whether
the object would float without any other external forces on it is irrelevant; the object can
always be pushed below the surface, and then the volume submerged is equal to the whole
volume of the object; for the maximum buoyant force, the object must be fully submerged
anyway.) Therefore, the only difference is ρf, which is greater for mercury, so eliminate C: the
maximum buoyant force is greater in mercury.
Pulmonary surfactant is a naturally occurring lipoprotein that greatly reduces the coefficient
of surface tension of the pulmonary fluid. Synthetic versions of pulmonary surfactants are
often given neonatally to treat respiratory distress syndrome. Which of the following best
explains this treatment?
A. Decreasing the surface tension coefficient decreases the amount of fluid in the lungs.
B. Decreasing the surface tension of pulmonary fluid allows the wet alveoli to expand more
easily during respiration. Correct Answer
C. Decreasing the surface tension of pulmonary fluid increases the force that holds the
alveoli open during respiration. Your Answer
D. Decreasing the surface tension of pulmonary fluid increases blood flow and decreases the
probability of blood clots. - ANSWER B.
The passage makes clear that surface tension is a binding force that resists increase in
surface area. Because the alveoli are small wet sacks (roughly spherical), a higher surface
tension would make these wet spheres of fluid more difficult to inflate, particularly when
they were deflated after exhalation (because a smaller sphere has a higher ratio of surface
area to volume). Choice B is therefore correct. Choice A can be eliminated because there is
nothing in the passage to support it: there is no implied relationship between surface
tension and total volume of fluid; though it is true that repiratory distress syndrome can lead
to increased fluid in the lungs, this is not a direct consequence of surface tension. Choice C is
a trap answer: surface tension is a force that tends to minimize surface area, not maximize it,
so it makes no sense that it would force the alveoli open rather than pulling them closed.
Choice D confuses blood flow with the pulmonary fluid.
Which of the following explains why a water droplet forms a roughly spherical shape if not
acted upon by external forces?
A. Gravitational force attracts all the mass to an equal distance from the center of mass,
forming a sphere.
3
, B. Surface tension pulls all the molecules apart as far as they can go, and the farthest apart
they can be is distributed in a spherical shape.
C. A sphere minimizes the surface area of the shape for a given volume, which yields the
lowest-energy state for the molecules.
D. The surface tension of the air, also a fluid, compresses the water into a spherical shape. -
ANSWER C.
The passage indicates at the end of the first paragraph that the lowest-energy state is one of
minimum surface area. Choice C is true, that a sphere encloses the greatest volume with the
lowest surface area of all three-dimensional shapes. Choice A is wrong because gravity is an
extremely small force here and has negligible effect, and furthermore, if the mass were all
an equal distance from the center, the shape would be a hollow sphere, not a solid one.
Choice B is wrong because surface tension comes from a force that pulls molecules together,
not apart; it's attractive, not repulsive. Choice D is wrong because air, as a gas, has
essentially zero surface tension (its intermolecular forces are very, very small).
What would happen if an aluminum coin (ρ = 2700 kg/m3, L = 1 cm, V = 1 × 10-8 m3) were
gently placed on the surface of water?
A. The buoyant force by itself would be sufficient to make the coin float.
B. The force of surface tension by itself would be sufficient to make the coin float.
C. Neither the buoyant force alone nor the force of surface tension alone would be sufficient
to make the coin float, but combined, they would make the coin float.
D. The coin would sink. - ANSWER B.
The maximum buoyant force for the coin is given by Fb = ρfVsubg, which for the given
situation is Fb = (1000)(10-8)(10) = 10-4 N. The weight of the coin is w = mg = ρcoinVg =
(2700)(10-8)(10) = 2.7 × 10-4 N. The weight is greater than the buoyant force, so eliminate
choice A: the buoyant force alone is not good enough. The maximum force of surface
tension is Fst,y = γL (twice, because the passage says that there are two of them). This comes
out to Ftotal surface tension = (2)(0.07)(0.01) = 1.4 × 10-3 N. That's greater than the weight,
so the surface tension alone can balance the weight and allow the coin to float.
Which of the following could also be units of the surface tension coefficient?
A. kg/m2
B. W/s2
4
100% CORRECT WELL DETAILED
ANSWERS|LATEST 2025-2026
UPDATE!!!|GRADED A+
The process by which the autonomic nervous system activates HCN channels is best
described by which of the following?
A. Sympathetic stimulation causes acetylcholine release, thereby activating cardiac tyrosine
kinase receptors, resulting in elevated cAMP levels.
B. Parasympathetic stimulation causes acetylcholine release, thereby activating tyrosine
kinase receptors, resulting in elevated cAMP levels.
C. Sympathetic stimulation causes epinephrine release, thereby activating G-protein coupled
receptors, resulting in elevated cAMP levels.
D. Parasympathetic stimulation causes epinephrine release, thereby activating G-protein
coupled receptors, resulting in elevated cAMP levels. - ANSWER C. The passage states
that cAMP binding opens and activates HCN channels, causing increased depolarization of
the heart, and therefore should increase heart rate. The sympathetic nervous system is
responsible for increasing heart rate, while the parasympathetic nervous system is
responsible for slowing it (choices B and D are wrong). Activation of the sympathetic nervous
system results in the release of norepinephrine from post-ganglionic neurons and
epinephrine from the adrenal medulla (choice A is wrong). Epinephrine acts on G-protein
coupled receptors, which activate adenylate cyclase to convert ATP to cAMP (choice C is
correct).
Modern civilization's insulation from natural phenomena has, of course, altered our
relationship to the weather substantially. The material successes of two centuries of applied
science have thoroughly dislodged the old deities as active presences in earthly affairs, and
our apparent control over nature has emptied it much of its metaphysical significance. Like
the wilds that once confronted a traveler just outside the city's gates, the weather has been
suburbanized and Disneyfied, its inclemencies signifying, for the most part, little more than
inconvenience. In the intensely humanized environment where much of the First World
lives—an environment so man-made as to often be called "dehumanizing"—we rarely pay
attention to the sky as a scene of drama and omen; it would seem that for many people the
TV weatherman has equal, if not more, phenomenal reality. And while we might find
vestiges of an earlier relationship in - ANSWER B. This is an Analogy question.
1
,A: No. In the last sentence of the passage, the author says, "The tragic irony of our
egocentric disenchantment of the world is this: we may one day come to 'own the weather'
only to find that the weather has turned as ugly and as rapacious as we." The right answer
for this question must therefore involve a scenario where someone assumes nature can be
dominated only to have it respond in a seemingly vengeful way. In this scenario, the
gardener exhibits neglect, thinking that nature will take care of itself; there is no attempt to
control or manipulate nature.
B: Yes. At the end of the passage, the author says, "The tragic irony of our egocentric
disenchantment of the world is this: we may one day come to 'own the weather' only to find
that the weather has turned as ugly and as rapacious as we." This extends the idea
introduced in the previous paragraph that by trying to control the weather, we may
unintentionally bring about catastrophic events. The right answer for this question must
therefore involve a scenario where someone assumes nature can be dominated only to have
it respond in a seemingly vengeful way. This answer choice involves the human attempt to
dominate nature; by introducing a foreign species of plant, the corporation is attempting to
manipulate nature for humans' (or at least the corporation's) benefit. Then, nature responds
back by negatively affecting humans' lives (or at least subverting the corporation's goals).
This is a good fit with the argument made in the passage.
C: No. While this answer contains the essential element of nature turning ugly in the end, it
lacks the element of attempted human dominance of nature. There is no information
provided in this choice about an attempt to subdue or control the dog.
D: No. This answer choice does not contain the "ugly" res
Which of the following is true of the differences between the forces exerted on a given
object by water and mercury? (ρ = 13500 kg/m3)
A. The maximum buoyant force is greater in mercury, and the maximum surface tension
force is greater in mercury.
B. The maximum buoyant force is greater in mercury, but the maximum surface tension
force is greater in water.
C. The maximum buoyant force is equal in both, but the maximum surface tension force is
greater in mercury.
D. The maximum buoyant force is equal in both, but the maximum surface tension force is
greater in water. - ANSWER A.
The coefficient of surface tension is greater in mercury, so eliminate choices B and D; the
maximum force of surface tension is greater in mercury. The force of buoyancy is given by Fb
= ρfVsubg, and g should not change. The maximum value of V should not either; the object
2
,can always be fully submerged, so the maximum value of V is just the total volume of the
object. (Note that the question does not ask about the value at any equilibrium, so whether
the object would float without any other external forces on it is irrelevant; the object can
always be pushed below the surface, and then the volume submerged is equal to the whole
volume of the object; for the maximum buoyant force, the object must be fully submerged
anyway.) Therefore, the only difference is ρf, which is greater for mercury, so eliminate C: the
maximum buoyant force is greater in mercury.
Pulmonary surfactant is a naturally occurring lipoprotein that greatly reduces the coefficient
of surface tension of the pulmonary fluid. Synthetic versions of pulmonary surfactants are
often given neonatally to treat respiratory distress syndrome. Which of the following best
explains this treatment?
A. Decreasing the surface tension coefficient decreases the amount of fluid in the lungs.
B. Decreasing the surface tension of pulmonary fluid allows the wet alveoli to expand more
easily during respiration. Correct Answer
C. Decreasing the surface tension of pulmonary fluid increases the force that holds the
alveoli open during respiration. Your Answer
D. Decreasing the surface tension of pulmonary fluid increases blood flow and decreases the
probability of blood clots. - ANSWER B.
The passage makes clear that surface tension is a binding force that resists increase in
surface area. Because the alveoli are small wet sacks (roughly spherical), a higher surface
tension would make these wet spheres of fluid more difficult to inflate, particularly when
they were deflated after exhalation (because a smaller sphere has a higher ratio of surface
area to volume). Choice B is therefore correct. Choice A can be eliminated because there is
nothing in the passage to support it: there is no implied relationship between surface
tension and total volume of fluid; though it is true that repiratory distress syndrome can lead
to increased fluid in the lungs, this is not a direct consequence of surface tension. Choice C is
a trap answer: surface tension is a force that tends to minimize surface area, not maximize it,
so it makes no sense that it would force the alveoli open rather than pulling them closed.
Choice D confuses blood flow with the pulmonary fluid.
Which of the following explains why a water droplet forms a roughly spherical shape if not
acted upon by external forces?
A. Gravitational force attracts all the mass to an equal distance from the center of mass,
forming a sphere.
3
, B. Surface tension pulls all the molecules apart as far as they can go, and the farthest apart
they can be is distributed in a spherical shape.
C. A sphere minimizes the surface area of the shape for a given volume, which yields the
lowest-energy state for the molecules.
D. The surface tension of the air, also a fluid, compresses the water into a spherical shape. -
ANSWER C.
The passage indicates at the end of the first paragraph that the lowest-energy state is one of
minimum surface area. Choice C is true, that a sphere encloses the greatest volume with the
lowest surface area of all three-dimensional shapes. Choice A is wrong because gravity is an
extremely small force here and has negligible effect, and furthermore, if the mass were all
an equal distance from the center, the shape would be a hollow sphere, not a solid one.
Choice B is wrong because surface tension comes from a force that pulls molecules together,
not apart; it's attractive, not repulsive. Choice D is wrong because air, as a gas, has
essentially zero surface tension (its intermolecular forces are very, very small).
What would happen if an aluminum coin (ρ = 2700 kg/m3, L = 1 cm, V = 1 × 10-8 m3) were
gently placed on the surface of water?
A. The buoyant force by itself would be sufficient to make the coin float.
B. The force of surface tension by itself would be sufficient to make the coin float.
C. Neither the buoyant force alone nor the force of surface tension alone would be sufficient
to make the coin float, but combined, they would make the coin float.
D. The coin would sink. - ANSWER B.
The maximum buoyant force for the coin is given by Fb = ρfVsubg, which for the given
situation is Fb = (1000)(10-8)(10) = 10-4 N. The weight of the coin is w = mg = ρcoinVg =
(2700)(10-8)(10) = 2.7 × 10-4 N. The weight is greater than the buoyant force, so eliminate
choice A: the buoyant force alone is not good enough. The maximum force of surface
tension is Fst,y = γL (twice, because the passage says that there are two of them). This comes
out to Ftotal surface tension = (2)(0.07)(0.01) = 1.4 × 10-3 N. That's greater than the weight,
so the surface tension alone can balance the weight and allow the coin to float.
Which of the following could also be units of the surface tension coefficient?
A. kg/m2
B. W/s2
4
