MCAT Sample Questions: Chemical and Physical Foundations
Below are examples of MCAT chemistry questions to help you get an understanding of the exam.
Chemical and Physical Foundations of Biological Systems Question #1
Choose the option that best describes what the basal layer of the epidermis and the innermost lining of the small intestine have in common.
A) The two are non-dividing tissues.
B) They are both derived from ectoderm.
C) The two are made up of squamous cells.
D) The cells of each option are connected by tight junctions.
Answer and Explanation
The correct answer is D. Both the basal layer of the epidermis and the innermost lining of the small intestine are epithelial tissues, and epithelial cells are held together by tight junctions that control what passes between them.
A is incorrect because both of these tissues are actually among the most rapidly dividing in the body. The basal layer constantly produces new keratinocytes that migrate upward, and the intestinal lining replaces itself roughly every 3-5 days.
B is incorrect because only the epidermis derives from ectoderm. The intestinal lining comes from endoderm, a classic embryology distinction worth memorizing.
C is incorrect because the basal layer contains cuboidal to columnar cells, not squamous cells. Squamous cells appear in the upper layers of the epidermis after they flatten during differentiation. The small intestine's lining is simple columnar epithelium, not squamous.
Chemical and Physical Foundations of Biological Systems Question #2
The heme enzyme indoleamine 2,3 dioxygenase (IDO) catalyzes Reaction 1, the first and rate-determining step of L-tryptophan (Compound 1) metabolism, and is an important enzyme of the human immune system.
Reaction 1
The IDO-catalyzed oxidation of Compound 1 by H₂O₂ does not occur. However, researchers have recently discovered that IDO-catalyzed oxidation of indole (Compound 3) by H₂O₂ (Reaction 2) does occur.
Reaction 2
Under the conditions employed, the number of catalytic turnovers appeared to stop at roughly 100, on average. A plot of the concentration of Compound 3 that was oxidized versus the concentration of H₂O₂ employed, at two different initial concentrations of IDO, gave the results shown in Figure 1.
Aerobic oxidation of Compound 3 in the presence of 18O-labeled H₂¹⁸O₂ resulted in the formation of 18O-labeled oxidation products (Table 1).
The formation of Compound 6 does not appear to be the result of a sequential oxidation process. Isotopically labeled Compound 4 does not exchange 18O for 16O in water over 3 hours, but Compound 6 completely loses its 18O label in unlabeled water over the same time period.
What change to the IR spectrum of the product mixture can be observed to monitor the progress of Reaction 2?
A) Appearance of a broad peak at 3400 cm–1
B) Disappearance of a broad peak at 3400 cm–1
C) Appearance of a sharp peak at 1700–1750 cm–1
D) Disappearance of a sharp peak at 1700–1750 cm–1
Answer and Explanation
The correct answer is C. As Reaction 2 progresses, a sharp peak appears in the 1700–1750 cm⁻¹ range, which corresponds to a carbonyl (C=O) stretch. Tracking the growth of this peak gives you a direct way to monitor product formation.
You need a working knowledge of IR spectroscopy, the functional group ranges, and the ability to identify the structural changes that occur between the reactants and products in Reaction 2. The product introduces a carbonyl group that the starting material lacks, making the appearance of that sharp C=O absorption the clearest spectral marker of reaction progress.
A is incorrect because a broad peak at 3400 cm⁻¹ signals an O–H or N–H stretch. If the reaction consumes an alcohol or amine to form the carbonyl-containing product, you'd expect this peak to shrink, not appear.
B is incorrect — while the disappearance of an O–H stretch at 3400 cm⁻¹ could, in principle, indicate reactant consumption, monitoring product formation is a more reliable and direct way to track reaction progress. The question asks what you can observe, and the carbonyl peak is the stronger diagnostic signal here.
D is incorrect because the 1700–1750 cm⁻¹ peak belongs to the product, not the reactant. You'd see this peak appear as the reaction moves forward, not disappear.
Chemical and Physical Foundations of Biological Systems Question #3
These kinetic parameters have been obtained for IDO-catalyzed oxidation of Compound 3 by H2O2 in the presence of L-Trp.
Considering the above data, what is the effect of L-Trp on the reaction?
A) L-Trp oxidizes Compound 3 directly
B) L-Trp is oxidized instead of Compound 3
C) L-Trp does not interact with the enzyme
D) L-Trp inhibits the enzyme
Answer and Explanation
The correct answer is D. The kinetic data show that as L-Trp concentration increases, the kcat value decreases. Since kcat represents the enzyme's turnover number, a declining kcat indicates that IDO produces less product when L-Trp is present.
A is incorrect because L-Trp is an amino acid, not an oxidizing agent. Nothing in the data suggests a direct chemical reaction between L-Trp and Compound 3 independent of the enzyme.
B is incorrect because the question specifically describes IDO-catalyzed oxidation of Compound 3. If L-Trp were simply acting as a competing substrate, you'd expect to see changes in Km rather than a clear drop in kcat. The data points to inhibition, not substrate competition.
C is incorrect because the data directly contradicts it. If L-Trp had no interaction with IDO, the kinetic parameters would remain unchanged regardless of L-Trp concentration. The decreasing kcat value indicates that L-Trp is affecting the enzyme.
Chemical and Physical Foundations of Biological Systems Question #4
Of the experiments, which can be utilized to demonstrate that Compound 6 isn’t formed from either Compound 4 or Compound 5 sequentially?
A) Conduct the reaction of Compound 4 with Compound 5, and identify the products.
B) Oxidize Compound 4 and Compound 5 with IDO/H2O2, and identify the products.
C) Reduce pure Compound 6 without added catalyst, and identify the products.
D) Conduct the reaction of Compound 2 with H2O2 without added catalyst, and identify the products.
Answer and Explanation
The correct answer is B. To prove that Compound 6 doesn't form sequentially from Compound 4 or Compound 5, you need to test whether IDO can convert either of those compounds into Compound 6 on its own.
Oxidizing Compound 4 and Compound 5 individually with IDO/H₂O₂ and checking the products gives you that answer directly. If neither produces Compound 6, you've ruled out the sequential pathway.
A is incorrect because reacting Compound 4 directly with Compound 5 without the enzyme tells you nothing about the IDO-catalyzed pathway. You're testing a non-enzymatic reaction that doesn't address whether IDO sequentially converts these intermediates.
C is incorrect because reducing Compound 6 without a catalyst proceeds in the reverse direction from the product and doesn't use IDO at all. Even if Compound 6 broke down into Compounds 4 or 5 under reduction, that wouldn't prove or disprove a forward sequential formation mechanism. Reverse reactivity doesn't confirm the directionality of the forward pathway.
D is incorrect because running the reaction of Compound 2 with H₂O₂ in the absence of IDO removes the enzyme entirely. You'd only observe non-catalyzed chemistry, which doesn't address whether IDO mediates a sequential conversion through Compound 4 or 5 on the way to Compound 6.
Chemical and Physical Foundations of Biological Systems Question #5
A researcher dissolves a weak acid (HA) with a pKa of 4.8 in a buffer solution at pH 7.4. Which of the following best describes the predominant form of the acid in solution and the ratio of conjugate base to acid?
A) HA predominates; the ratio of A⁻ to HA is approximately 1:400
B) A⁻ predominates; the ratio of A⁻ to HA is approximately 400:1
C) HA and A⁻ are present in roughly equal amounts
D) A⁻ predominates; the ratio of A⁻ to HA is approximately 40:1
Answer and Explanation
The correct answer is B. Use the Henderson-Hasselbalch equation and plug in the values. The conjugate base dominates by a ratio of roughly 400:1.
A is incorrect because it reverses the relationship entirely. HA would predominate only if the pH were below the pKa, meaning the environment was acidic enough to keep the proton attached.
C is incorrect because equal concentrations of HA and A⁻ occur only when pH equals pKa exactly. At pH 4.8, you'd see a 1:1 ratio. The 2.6-unit gap between the solution pH and the pKa makes equal distribution impossible, so the equilibrium has shifted dramatically toward A⁻.
D is incorrect because it underestimates the ratio by a full order of magnitude. A ratio of 40:1 corresponds to log(40) ≈ 1.6, which would place the pH at 4.8 + 1.6 = 6.4. At pH 7.4, the actual ratio is 10 times larger. On the MCAT, pay close attention to whether you're computing the log value correctly.
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Read Passage 4 from the CARS section of our MCAT Practice Test
Some years ago the Director of the Leipsic Conservatorium gave the writer a complete record of the number of graduates of the conservatory from the founding to the late nineties. Of the thousands of students who had passed through the institution only a few had gained wide prominence. Hardly one student in one hundred had won his way into the most voluminous of the musical biographical dictionaries. The proportion of distinguished graduates to those who fail to gain renown is very high at Leipsic compared with many other institutions. What becomes of the thousands of students all working frantically with the hope of becoming famous pianists? Surely, so much earnest effort can not be wasted even though all can not win the race? Those who often convince themselves that they have failed go on to perform a more useful service to society than the laurelcrowned virtuoso. Unheralded and unapplauded, they become the teachers, the true missionaries of Frau Musik to the people.
What is it then, which promotes a few “fortunate” ones from the armies of students all over America and Europe and makes of them great virtuosos? What must one do to become a virtuoso? How long must one study before one may make a début? What does a great virtuoso receive for his performances? How long does the virtuoso practice each day? What exercises does he use? All these and many more similar questions crop up regularly in the offices of music critics and in the studios of teachers. Unfortunately, a definite answer can be given to none, although a great deal may be learned by reviewing some of the experiences of one who became great.
Some virtuosos actually seem to be born with the heavenly gift. Many indeed are sons and daughters of parents who see their own demolished dreams realized in the triumphs of their children. When little Nathan creeps to the piano and quite without the help of his elders picks out the song he has heard his mother sing,— all the neighbors in Odessa know it the next day. “A wonder child perhaps!” Oh happy augury of fame and fortune! Little Nathan shall have the best of instruction. His mother will teach him at first, of course. She will shape his little fingers to the keyboard. She will sing sweet folk melodies in his ear,—songs of labor, struggle, exile. She will count laboriously day after day until he “plays in time.” All the while the little mother sees far beyond the Ghetto,—out into the great world,—grand auditoriums, breathless crowds, countless lights, nobles granting trinkets, bravos from a thousand throats, Nathan surrounded by endless wreaths of laurel,—Oh, it is all too much,—”Nathan! Nathan! you are playing far too fast. One, two, three, four,—one, two, three, four,—there, that is the tempo Clementi would have had it. Fine! Some day, Nathan, you will be a great pianist and—” etc., etc.
Nathan next goes to the great teacher. He is already eight years old and fairly leaping out of his mother’s arms. Two years with the teacher and Nathan is probably ready for a début as a wonder child. The critics are kind. If his parents are very poor Nathan may go from town to town for awhile being exhibited like a trained poodle or a tiny acrobat. The further he gets from home the more severe his critics become, and Nathan and his mother hurry back to the old teachers, who tell them that Nathan must still practice long and hard as well as do something to build up his general education. The world in these days looks askance at the musician who aside from his keyboard accomplishments is a numskull. More sacrifice for Nathan’s mother and father,—but what are poverty and deprivation with such a goal in sight? Nathan studies for some years in the schools and in the high schools as well as at the conservatory. In the music school he will doubtless spend six years in all,—two years in the post-graduate or master classes, following the regular four-year course. When sufficiently capable he will take a few pupils at a kopeck or so per lesson to help out with the family expenses…
Unfortunately, the number of virtuosos who have been taught exclusively in America is really very small. It is not a question of ability upon the part of the teacher or talent upon the part of the pupil. It is entirely a matter of the attitudes of the teacher, the pupil and the pupil’s home advisers. Success demands strong-willed discipline and the most lofty standards imaginable. Teachers who have taught for years in America have returned to Europe, doubled and quadrupled their fees, and, under old-world surroundings and with more rigid standards of artistic work, have produced results they declare would have been impossible in America. The author contends that these results would have been readily forthcoming if we in America assumed the same earnest, persistent attitude toward the work itself. If these words do no more than reach the eyes of some of those who are advising students wrongly in this matter they will not have been written in vain. The European concert triumphs of Mrs. H. H. A. Beach, whose training was received wholly in the United States, is an indication of what may be achieved in America if the right course is pursued. Conditions are changing rapidly in our country, particularly in the wonderful West and Middle-West. It seems likely that many pianists without foreign instruction of any kind will have as great success in our concert field as have many of our best opera singers who have never had a lesson ‘on the other side.’
Which of the following statements are true, according to the opinions expressed in the passage?
A) National — or international — acclaim is the highest reward a pianist can receive
B) It is easier to win acclaim when a pianist travels from his or her home country
C) Americans face insurmountable difficulties on the road to becoming a virtuoso pianist
D) A pianist's success primarily depends on internal, rather than external, factors
Correct Answer: D
Answer and Explanation
Answer D is correct because the author repeatedly emphasizes that attitude, discipline, and motivation drive a virtuoso's success more than birthplace or training location. The passage states that the gap between American and European results "is not a question of ability upon the part of the teacher or talent upon the part of the pupil" but rather "entirely a matter of the attitudes of the teacher, the pupil and the pupil's home advisers." The author reinforces this by pointing to Mrs. H.H.A. Beach, an American-trained pianist who achieved European-level concert success, proof that internal drive can overcome external disadvantage.
Answer A is incorrect because the author doesn't treat international fame as the ultimate reward. In the opening paragraph, the author describes graduates who never achieve fame as performing "a more useful service to society than the laurel-crowned virtuoso" by becoming "the true missionaries of Frau Musik to the people." If the author believed acclaim was the highest possible reward, calling teaching a more useful service would contradict that belief.
Answer B is incorrect because the passage says the opposite. Nathan's experience shows that traveling away from home made success harder, not easier: "the further he gets from home the more severe his critics become." Audiences and critics closer to home are presented as more favorable and forgiving.
Answer C is incorrect because "insurmountable" is too strong. The author acknowledges Americans face real disadvantages compared to Europeans but explicitly argues those disadvantages can be overcome. Mrs. Beach's European concert success while trained entirely in the United States directly disproves the idea that the obstacles are impossible to clear.
Critical Analysis and Reasoning Question #2
The author's attitude towards Leipsic graduates who do not become virtuosos can be best described as…
A) Remorseful and conservative
B) Patronizing and objective
C) Disinterested and careless
D) Hopeful and sincere
Correct Answer: D
WAnswer and Explanation
Answer D is correct because the author treats non-famous graduates with genuine warmth and optimism. The hopeful element appears when the author reframes their outcome as valuable rather than failed. They become "the teachers, the true missionaries of Frau Musik to the people," performing "a more useful service to society than the laurel-crowned virtuoso." The sincere element appears in the author's rhetorical question: "Surely, so much earnest effort can not be wasted even though all can not win the race?" The author is personally invested in these pianists' worth, not just reporting on it dispassionately.
Answer A is incorrect because remorseful implies sadness or regret, and the author expresses neither. The author doesn't lament the non-famous graduates' outcome or describe their conservatory years as wasted. The tone is uplifting, not mournful. "Conservative" also misses because the author speaks openly and positively about their contributions rather than holding back.
Answer B is incorrect because patronizing implies a sense of superiority or condescension, and the author shows none. The passage doesn't belittle these pianists or talk down to them. "Objective" also fails because the author's language is clearly opinion-driven, calling them "true missionaries" and describing their work as "a more useful service" are personal judgments, not neutral observations.
Answer C is incorrect because the author is clearly invested in these pianists' futures. The rhetorical question about whether "so much earnest effort" can be wasted shows active concern, not indifference. An author who was disinterested would skip the first paragraph entirely instead of spending it reframing non-fame as a meaningful contribution.
Critical Analysis and Reasoning Question #3
Which of the following best describes the author's purpose in writing this text?
A) To provide aspiring virtuosos with a step-by-step guide to achieving success
B) To console aspiring virtuosos who have failed to attain their initial goals
C) To evaluate the assumptions of aspiring virtuosos and their teachers
D) To critique those who push young people into the desire for virtuoso-level fame
Correct Answer: C
Answer and Explanation
Answer C is correct because the passage spends its entirety examining what people believe about how virtuosos are made. The author questions the assumption that talent alone determines success, challenges the belief that European training is mandatory, and pushes back on the idea that American students can't compete. The passage evaluates each of these assumptions by presenting evidence and drawing conclusions that challenge conventional thinking about what it takes to become a virtuoso.
Answer A is incorrect because the author explicitly acknowledges that no step-by-step formula exists. After posing questions about practice time, study length, and exercises, the author states that "unfortunately, a definite answer can be given to none." A step-by-step guide requires definite answers, and the author makes clear those answers don't exist. The passage analyzes the factors behind success. It doesn't prescribe a process.
Answer B is incorrect because consolation occupies only a few sentences in the first paragraph. The author briefly acknowledges non-famous graduates and reframes their contribution, but then moves on to spend the majority of the passage examining how virtuosos are produced and whether Americans can compete with Europeans. Consolation is a minor aside, not the driving purpose.
Answer D is incorrect because the author doesn't criticize the families or teachers who push young people toward fame. Nathan's mother’s dreams for her son are presented as earnest and loving, not harmful or misguided. The author also speaks positively about the role of parents and teachers in shaping a virtuoso's success, calling their attitudes the primary determinant. The tone is supportive of the pursuit, not critical of it.
Critical Analysis and Reasoning Question #4
Which of the following details, if true, would most undermine the author's overall argument?
A) The report provided by the Conservatorium Director was incorrect, and many more graduates achieved fame than the author initially reported
B) Data suggesting that the greatest factor predicting success is one's country of origin or training
C) Knowledge that no successful, world-renowned virtuoso has ever had a son or daughter achieve equivalent fame
D) Personal testimony from successful virtuosos about the incredible pressures they faced during childhood
Correct Answer: B
Answer and Explanation
Answer B is correct because the author's central argument is that internal factors matter more than external circumstances like where you were born or trained. The author states directly that the gap between American and European results is "entirely a matter of the attitudes" involved, and offers Mrs. Beach as evidence that American training can produce European-level success. If data proved that country of origin was actually the greatest predictor of success, that foundational claim collapses.
Answer A is incorrect because the Conservatorium data is a scene-setting detail, not the structural foundation of the argument. Even if more graduates achieved fame than reported, the author's core claims about what drives success would remain intact. The passage doesn't depend on the exact failure rate at Leipsic — it uses that data to introduce the question of what separates successful virtuosos from everyone else. Correcting the numbers changes the introduction, not the argument.
Answer C is incorrect because the author never argues that virtuoso parents produce virtuoso children through genetics. The author acknowledges that many virtuosos come from musical families, but attributes this to parental motivation and sacrifice. If no virtuoso's child ever matched their parent's fame, the author would likely point to attitude and discipline as the reason rather than view it as a contradiction.
Answer D is incorrect because it would actually strengthen the argument. The author already describes the hardships Nathan's family endures. Personal testimony from real virtuosos about childhood pressures would reinforce the passage's portrayal of the difficult path to success, not undermine it.
Critical Analysis and Reasoning Question #5
In the last paragraph, what does the author mean when saying "It is entirely a matter of the attitudes of the teacher, the pupil, and the pupil's home advisers?"
A) If both teachers and students went to Europe, success would be guaranteed
B) If students performed in Europe, success would be likely
C) If America held art to the same standard as Europe and teachers tried to push this standard on students, success would likely ensue
D) If America hosted the same concerts in Europe and if more students performed in these concerts, then success would likely be ensured
Correct Answer: C
Answer and Explanation
Answer C is correct because the author spends the final paragraph arguing that the gap between American and European results comes down to standards and attitudes, not geography. Teachers who moved to Europe "doubled and quadrupled their fees, and, under old-world surroundings and with more rigid standards of artistic work, have produced results they declare would have been impossible in America."
Answer A is incorrect because "guaranteed" is far too strong, and the author's point isn't about physically relocating to Europe. The passage argues that European success comes from higher standards and more disciplined attitudes. Moving to Europe without changing one's attitude wouldn't help, according to the author's logic.
Answer B is incorrect because performing in Europe isn't the author's point. The passage distinguishes between where you perform and how you train. The author argues that training with the right attitudes and standards is what produces results. Nathan's experience shows that performing abroad without sufficient preparation actually leads to harsher criticism, not success.
Answer D is incorrect because it misreads the author's argument as being about concert venues and performance opportunities. The author never discusses hosting European concerts in America or increasing the number of performances. More concerts don't fix the underlying attitude problem the author identifies.
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Practice Biological and Biochemical Foundations of Living Systems MCAT Questions
Below are sample MCAT biochemistry and biology questions to help you master the section.
Biological and Biochemical Foundations of Living Systems Question #1
A new test involving precipitation has been developed to find proteins in urine. However, complications have arisen due to precipitation of calcium phosphate. Which of the following procedures could prevent the precipitation of the salt?
A) Adding a buffer in order to maintain a high pH
B) Adding a buffer so a neutral pH can be maintained
C) Adding calcium hydroxide to the test
D) Adding sodium phosphate to the test
Answer and Explanation
The correct answer is B. Calcium phosphate precipitates more readily in alkaline conditions because higher pH increases the concentration of phosphate ions (PO₄³⁻) available to bind with calcium.
A is incorrect because a high pH does the exact opposite of what you want. Alkaline conditions favor the formation of PO₄³⁻, which binds calcium more readily and increases precipitation. Buffering at high pH would lock in the very conditions that cause the complication.
C is incorrect because adding calcium hydroxide increases the concentration of calcium ions in the solution. More Ca²⁺ means a greater ion product relative to the solubility constant (Ksp), which pushes the system further toward precipitation. You'd be adding fuel to the fire.
D is incorrect for the same reason in reverse. Sodium phosphate adds more phosphate ions to the solution, again increasing the ion product and driving more calcium phosphate out of solution. Whenever you're trying to prevent a precipitate from forming, adding either of its component ions is the wrong move.
Biological and Biochemical Foundations of Living Systems Question #2
The researchers chose a concentration of 0.3 mM IAA as the working concentration for any additional studies instead of 1 mM or 2 mM. What is the likely reason for this?
A) The lower concentration of IAA gave the largest Na+ response.
B) Higher concentrations induced significant cytotoxicity.
C) The solubility of IAA was not high enough.
D) The researchers were trying to mimic control conditions as closely as possible.
Answer and Explanation
The correct answer is B. When a researcher deliberately chooses a lower drug concentration rather than a higher one, the most common reason in experimental biology is cytotoxicity. At 1 mM and 2 mM, IAA (iodoacetamide/iodoacetic acid) likely killed too many cells, destroying their membrane integrity and causing lysis.
A is incorrect because choosing a working concentration is about maintaining experimental validity. Even if 0.3 mM produced a large Na⁺ response, that alone wouldn't explain why the higher concentrations were abandoned. The more fundamental issue is whether the cells survived long enough to generate reliable data.
C is incorrect because IAA is a small organic molecule that dissolves readily at low-millimolar concentrations. Solubility issues typically arise at much higher concentrations, and 1-2 mM is well within the soluble range for compounds like IAA. Nothing in the experimental design suggests solubility was a limiting factor.
D is incorrect because the entire point of adding IAA is to inhibit glycolysis and observe the downstream effects. Mimicking control conditions would defeat the purpose of the experiment. Researchers want a concentration that produces a clear metabolic disruption without killing the cells.
Biological and Biochemical Foundations of Living Systems Question #3
The myocellular transmembrane Na+ gradient is important for proper cellular function. During septic shock, disruption of Na+ homeostasis often occurs and leads to decreased membrane potential and increased intracellular Na+.
It has been found that failure of cellular energy metabolism is a common symptom in septic patients who do not respond to therapeutics. Because normal intracellular levels of Na+ are maintained by the Na+K+ ATPase, it is important to understand how metabolic energy production is linked to cation transport.
Researchers are interested in whether the energy used for ion transport is derived from glycolysis or oxidative phosphorylation. This information would provide a better understanding of myocellular damage that occurs during critical illness. Experiments were conducted to evaluate the effects of glycolytic inhibition on cellular Na+ and K+ concentrations and lactate production in rat skeletal myocytes.
Rat skeletal muscle fibers were extracted and incubated in normal media (control), glucose-free media (G(–)), and glucose-free media with various concentrations of the glycolytic inhibitor iodoacetate (IAA). IAA directly prevents the formation of 1,3-bisphosphoglycerate.
After one hour in the media, the muscle tissues were assayed for intracellular Na+ and K+ content and lactate production. Cellular viability was determined by measuring the amount of lactate dehydrogenase (LDH) released, as LDH release is an indicator of cell death. The results are displayed in Figure 1.
Figure 1 Effects of glycolytic inhibition on intracellular Na+ and K+ content and lactate production with cellular viability measured by LDH release. (Note: The * indicates p < 0.05 versus control.)
The researchers also examined the effect disruption of oxidative phosphorylation had on Na+ and K+ content. Inhibition of oxidative phosphorylation was caused by carbonyl-cyanide m-chlorophenylhydrazone (CCCP), an ionophore that allows protons to move freely through membranes. No correlation between Na+ and K+ content and oxidative phosphorylation was found.
The information in the passage suggests that glycolysis:
A) is important for maintaining normal Na+ and K+ levels in skeletal muscle.
B) facilitates membrane permeability in skeletal muscle.
C) impedes the function of the Na+ and K+ ATPase in skeletal muscle.
D) is regulated by the Na+ and K+ ATPase in skeletal muscle.
Answer and Explanation
The correct answer is A. The passage uses IAA to show what happens when you shut down glycolysis in skeletal muscle cells.
B is incorrect because the passage shows that glycolysis maintains ion gradients through active transport, not by altering membrane permeability. A change in permeability would mean the membrane itself became leakier, but the pump that moves ions against their gradients loses its energy supply. The membrane isn't the problem; the energy deficit is.
C is incorrect because it reverses the relationship entirely. Glycolysis supports the Na⁺/K⁺ ATPase by providing ATP. When glycolysis is inhibited by IAA, pump function declines. Glycolysis enables the pump. The passage data make this relationship clear: Less glycolysis is associated with worse pump performance, not better.
D is incorrect because it flips the directionality of the cause-and-effect relationship. The passage demonstrates that glycolysis affects Na⁺/K⁺ ATPase function, not the other way around. IAA inhibits glycolysis first, and ion imbalance follows as a downstream consequence. The data do not suggest that the ATPase regulates glycolytic activity.
Biological and Biochemical Foundations of Living Systems Question #4
If the effects of IAA treatment in nerve cells are the same as those observed in myocytes, which feature of an action potential would be most affected by IAA treatment?
A) Initiation of depolarization
B) Rising phase of depolarization
C) Falling phase to undershoot
D) Return to resting potential
Answer and Explanation
The correct answer is D. From the passage, you know that IAA inhibits glycolysis, which reduces ATP production, which in turn cripples the Na⁺/K⁺ ATPase. Now apply that same effect to nerve cells.
A is incorrect because depolarization initiates when a stimulus opens voltage-gated Na⁺ channels, allowing sodium to rush in passively along its electrochemical gradient. No ATP is required to open those channels or to drive the initial inward current. IAA treatment wouldn't prevent a neuron from reaching threshold, at least not directly or immediately.
B is incorrect because the rising phase is driven entirely by the passive influx of Na⁺ through voltage-gated sodium channels. Once the threshold is reached, rapid depolarization to +30 mV occurs without energy expenditure. The speed and magnitude of the rising phase depend on channel density and sodium gradient, not on ATP availability in the short term.
C is incorrect because the falling phase and undershoot result from voltage-gated K⁺ channels opening and allowing potassium to flow out of the cell passively. Delayed rectifier K⁺ channels drive repolarization, and their slow closing causes the undershoot below resting potential. None of these events requires ATP.
Biological and Biochemical Foundations of Living Systems Question #5
A mutation in the gene encoding hexokinase results in an enzyme with a significantly increased Km for glucose. Which of the following best predicts the physiological consequence of this mutation in cells that rely primarily on glycolysis for ATP production?
A) The rate of glycolysis will increase because the mutant enzyme binds glucose more tightly.
B) The rate of glycolysis will decrease at normal physiological glucose concentrations.
C) Pyruvate production will be unaffected because downstream enzymes compensate for the change.
D) The cell will shift entirely to oxidative phosphorylation to meet its energy demands.
Answer and Explanation
The correct answer is B. Km represents the substrate concentration at which an enzyme operates at half its maximum velocity. An increased Km means the enzyme requires a higher concentration of glucose to achieve the same catalytic rate.
A is incorrect because it confuses the direction of the Km change. An increased Km means weaker substrate binding, not tighter binding. A lower Km value indicates a higher affinity for glucose.
C is incorrect because downstream enzymes cannot compensate for reduced substrate input. Glycolysis operates as a sequential pathway. Each enzyme depends on the product of the preceding reaction. If hexokinase produces less glucose-6-phosphate, phosphofructokinase (PFK-1) receives less fructose-6-phosphate, and every subsequent step processes proportionally less substrate. Downstream enzymes don't generate their own substrates; they can only work with substrates that arrive from upstream.
D is incorrect because the shift to oxidative phosphorylation depends on substrate availability, not just enzyme preference. Oxidative phosphorylation requires acetyl-CoA, which comes from pyruvate via pyruvate dehydrogenase, and pyruvate production itself depends on glycolysis. If glycolysis slows, less pyruvate reaches the mitochondria, thereby limiting oxidative phosphorylation. Cells relying primarily on glycolysis may also lack the mitochondrial capacity to fully compensate through oxidative pathways, making a complete shift physiologically unrealistic.
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Psychological, Social, and Biological Foundations of Behavior MCAT Questions
Below are sample MCAT psych/soc and biological foundations of behavior questions.
Psychological, Social, and Biological Foundations of Behavior Question #1
Which of the following statements represents the prediction of “cultural capital” as a concept:
A) The cultural distinctions we associate with young people will be considered to have a higher value within a society.
B) The cultural practices of all classes will converge over time with improved communication.
C) Class-based cultural distinctions will gradually decrease in importance in the midst of a recession since most people will have less money.
D) The cultural distinctions that are associated with the upper classes of a society will be considered to have a higher value within the society.
Answer and Explanation
The correct answer is D. Cultural capital, a concept developed by the sociologist Pierre Bourdieu, refers to the non-financial social assets that confer status and power within a society.
A is incorrect because cultural capital is tied to class, not age. Young people don't hold a privileged position in Bourdieu's framework simply because they are young. Youth culture may be popular, but popularity and cultural capital are different things. Cultural capital specifically tracks the tastes and practices that dominant social classes use to distinguish themselves and maintain power.
B is incorrect because cultural capital theory actually predicts the opposite. Rather than cultural practices converging across classes, Bourdieu argued that upper classes continuously shift their cultural markers to maintain distinction. When lower classes adopt upper-class practices, the upper class moves on to new ones. Improved communication might spread awareness of upper-class culture, but access and authentic fluency in those practices remain class-bound.
C is incorrect because cultural capital operates independently of economic conditions. A recession reduces financial capital, but class-based cultural distinctions don't disappear when everyone has less money. Someone who lost their wealth in a downturn still carries their education, speech patterns, and cultural knowledge. Bourdieu's entire point is that cultural capital functions as a separate axis of social advantage that persists even when economic circumstances shift.
Psychological, Social, and Biological Foundations of Behavior Question #2
Select the following correlation that supports the “bystander effect.”
A) In an emergency circumstance, the number of bystanders present correlates positively with the amount of time it takes for anyone to offer assistance.
B) In an emergency circumstance, the number of bystanders present correlates negatively with the amount of time it takes for anyone to offer assistance.
C) In an emergency circumstance, the number of bystanders present correlates positively with how onlookers qualify a situation to be an emergency.
D) In an emergency circumstance, the number of bystanders present correlates negatively. with how onlookers qualify a situation to be an emergency.
Answer and Explanation
The correct answer is A. The bystander effect, first documented by psychologists John Darley and Bibb Latané, describes a counterintuitive phenomenon: The more people who witness an emergency, the longer it takes for anyone to help. A positive correlation between bystander count and response time captures this relationship perfectly: As one variable increases, so does the other. More witnesses, longer delays.
B is incorrect because a negative correlation would mean more bystanders lead to faster help, which is the exact opposite of the bystander effect. That would describe a world in which crowds mobilize quickly, contradicting decades of research showing the opposite pattern.
C is incorrect because the bystander effect doesn't predict that larger crowds become better at identifying emergencies. If anything, pluralistic ignorance pushes in the other direction, as people in larger groups are more likely to downplay the severity of a situation because everyone else appears calm. A positive correlation between crowd size and emergency recognition contradicts the mechanism.
D is incorrect and represents a tempting partial answer. Pluralistic ignorance suggests that larger crowds may be less likely to label a situation as an emergency, suggesting a negative correlation between bystander count and emergency recognition. However, the bystander effect is fundamentally defined by the delay in helping behavior, not by perception of the emergency. Answer A captures the core prediction of the phenomenon more directly and completely.
Psychological, Social, and Biological Foundations of Behavior Question #3
The illness experience shapes the way that people use health information. For patients with a rare health disorder, which is defined as a medical condition that affects fewer than 200,000 individuals living in the United States, online sources of information tend to be particularly important.
An example of a rare disorder is Amyotrophic Lateral Sclerosis (ALS), also known as “Lou Gehrig’s disease.” ALS results from the progressive loss of motor nerves and affects about 1 out of 100,000 people. About 10% of people with ALS have a familial form of the condition, which is caused by an inherited genetic mutation. Aside from the familial form, the cause of ALS is largely unknown, though it is believed that the disorder results from both genetic and environmental factors.
Having a rare medical condition, such as ALS, can make it difficult to meet and interact with others who have the same rare disorder. Despite great distances, online communication provides a form of social interaction for those facing an uncommon health problem. Virtual peer networks provide vital social support for those who are affected by a rare disorder.
Research has found that women with rare disorders are more likely to access online support networks than men with rare disorders. Relationships formed through online support networks often become a meaningful part of a person’s identity. Individuals with rare disorders report that relating to others who have the same condition is often easier than trying to relate to friends or family members who do not share their condition.”
Which statement best represents a threat to social identity? A young woman with a rare disorder:
A) believes that others treat her as less capable, and then she starts to see herself as deficient.
B) becomes discouraged when she hears that others with rare disorders are treated as less capable.
C) hides her disorder from others in order to project more confidence in social situations.
D) reveals her disorder to friends, who mistakenly assume that it is a social limitation.
Answer and Explanation
The correct answer is B. Social identity refers to the part of a person's self-concept that comes from belonging to a group. For someone with a rare disorder who has built connections through online support networks, that community becomes a meaningful part of how they see themselves.
A is incorrect because it describes a threat to personal identity rather than social identity. The woman internalizes how others treat her individually and begins to view herself as deficient. While damaging, this process operates at the individual level, as her personal self-concept deteriorates based on direct interpersonal treatment. You might also recognize elements of the looking-glass self or self-fulfilling prophecy here, but neither is a social identity threat.
C is incorrect because hiding a disorder to project confidence describes stigma management or impression management, not a threat to social identity. The woman is actively controlling how others perceive her as an individual. She's navigating personal social interactions strategically, which relates to Goffman's concept of self-presentation rather than group-based identity concerns.
D is incorrect because friends making incorrect assumptions about her limitations represents a misunderstanding at the interpersonal level. The friends are misjudging her individual capabilities, which affects her personal interactions but doesn't target her group membership. A social identity threat requires that the stigma or devaluation be directed at the group she identifies with, not just at her personally.
Psychological, Social, and Biological Foundations of Behavior Question #4
Over the course of ten years, a rare disorder increases in prevalence such that it eventually affects more than 200,000 people in the United States. Based on the passage and this scenario, which prediction is most consistent with the sociological paradigm of symbolic interactionism?
A) As the number of affected individuals increases, government research funding increases.
B) Affected individuals are less likely to conceal their condition as it becomes less stigmatized.
C) As more people with the condition are treated, it receives less attention as a health concern.
D) Insurance coverage for the condition becomes more likely as more people require treatment.
Answer and Explanation
The correct answer is B. Symbolic interactionism focuses on how meaning is constructed through people's interpretations of symbols, labels, and each other's behavior in face-to-face encounters. When a disorder is rare, people with the condition carry a stigmatized label.
A is incorrect because government funding decisions operate at the macro-structural level. Policies on research allocation involve institutional actors, political processes, and bureaucratic systems, all of which fall squarely within functionalist or conflict-theoretical frameworks. Symbolic interactionism doesn't analyze how large institutions distribute resources; it examines how individuals create meaning through direct interaction.
C is incorrect because reduced attention to a health concern as treatment expands describes a macro-level societal trend. Whether a condition receives more or less public attention involves media coverage, institutional priorities, and large-scale social dynamics. Symbolic interactionism wouldn't generate predictions about aggregate attention patterns. It would ask how individuals with the condition experience and negotiate meaning in their personal interactions.
D is incorrect because insurance coverage is determined by institutional and economic forces — insurance companies, regulatory bodies, and market dynamics. Expanding coverage based on population need is a structural response, not something that emerges from face-to-face meaning-making. Conflict theorists might analyze who benefits from coverage decisions, and functionalists might examine how insurance serves societal stability, but symbolic interactionism stays focused on the interpersonal level where stigma, identity, and meaning are negotiated daily.
Psychological, Social, and Biological Foundations of Behavior Question #5
Which research project best represents a macrosociological approach to studying the social support networks mentioned in the passage?
A) A researcher follows the conversation of participants who post messages in an online support forum.
B) A researcher interviews patients who participate in a local hospital’s support group for rare disorders.
C) A researcher surveys patients for reasons that they joined an online support group for their disorder.
D) A researcher tracks how the number of websites dedicated to rare disorders has changed over time.
Answer and Explanation
The correct answer is D. Macrosociology examines large-scale social structures, institutions, and patterns across populations over time. Tracking how the number of websites dedicated to rare disorders changes over a period reveals how healthcare infrastructure evolves, how digital resources expand or contract for specific communities, and how society organizes around health issues at a structural level.
A is incorrect because following conversations in an online forum analyzes individual interactions and communication patterns between specific people. Observing how participants talk to each other, what language they use, and how they support one another is classic microsociology. It's studying meaning-making and social dynamics at the interpersonal level, exactly the kind of work symbolic interactionists would conduct.
B is incorrect because interviewing individual patients about their experiences in support groups focuses on personal narratives, emotions, and face-to-face group dynamics. The researcher engages directly with individuals in small groups, exploring how they experience social support on a personal level. Interviews are a hallmark microsociological method that prioritizes depth of individual experience over breadth of societal trends.
C is incorrect because surveying patients about their personal reasons for joining a support group collects individual-level motivations. Even though surveys can sometimes serve macrosociological research when applied to large populations to identify structural patterns, the focus here is on why specific people made specific choices. Personal motivation is a microsociological variable; it tells you about individual decision-making, not about how society organizes health resources at scale.
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