MCAT Question of the Day

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MCAT Question of the Day
2013-11-29 14:02:30

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  1. A student places metal X into a solution of MS04 and sees a new metal coating forming over metal X.  Which of the following is true regarding this scenario?
    a. Metal M is being reduced
    b. Metal M is being oxidized.
    c. Metal M is undergoing a non-redox reaction with Metal X
    d.  The answer cannot be determined from the given information.
    Metal M is being reduced.

    The new metal coating onto metal X must be metal M because there is no other substance that could be adding in this scenario.  We therefore know that metal M is going from M2+ to M and must be gaining electrons; it is being reduced, making (A) the correct answer.
  2. R2NH and a hydrochloride  are produced in a reaction between:
    A. an alkyl halide and RNH2
    B. an alkyl halide and NH3
    C. a halide ion and R4n+
    D. a carboxylic amide and water
    A. an alkyl halide and RNH2

    Amines can be alkylated with alkyl halides.  R2NH is the alkylated form of RNH2.  A hydrocchloride is produced between the halide group of the alkyl halide and the substituted proton of the amine.  Thus, the reactants are RNH2 and an alkyl halide.  The correct answer is (A).
    (this multiple choice question has been scrambled)
  3. Which of the following molecules is least polar?
    a. SH2
    b. H2O
    c. CO2
    d. CCl2H2

    • The 3-dimensional geometry of each of the molecules is important to consider to evaluate its polarity. SH2
    • may appear to be a linear molecule in 2 dimensions, but it actually has
    • bent geometry due to the two lone pairs on the sulfur atom. This
    • creates a dipole in the molecule. The same geometry is seen in H2O, making it also incorrect. CCl2H2
    • also may appear to be symmetrical (and therefore nonpolar) in 2
    • dimensions, but will take on tetrahedral geometry where the two chlorine
    • atoms will point off at different angles from the two hydrogen atoms
    • (no matter their actual placement on the carbon atom) leaving a dipole
    • in the molecule as well. CO2 is a linear molecule and will not have a net dipole due to the symmetry of the two oxygen atoms.
  4. Which of the following statements is true regarding a system to which heat energy is
    added at a constant rate? Assume the system is open and exposed to air.
    A. The rate of heat loss to the environment is independent of the temperature of the environment.
    B. The temperature will rise linearly.
    C. The system will reach a maximum temperature when the rate of heat loss is equal to the rate of heat input.
    D.  The entropy of the system will decrease as the temperature increases.
    • (A)is incorrect because the ambient temperature determines the rate of
    • heat loss; a system whose environment is the same temperature will not lose heat to its environment, while a system whose environment is much colder will lose heat to its environment quickly. (B) is incorrect
    • because as the temperature rises, the rate of heat loss increases (see the explanation for (A) regarding the rate of heat loss vs. temperature difference). (C) is the correct answer because as the temperature rises
    • and the rate of heat loss increases, the rate of heat loss will eventually match the rate of heat input. Only a closed system which
    • loses no heat to its environment can have an infinite rise in temperature. (D) is incorrect because as temperatures rise, molecules
    • move more quickly and in more disorderly patterns, and therefore entropy
    • rises with temperature.
  5. Which of the following effects on urine production would be expected if there
    were vasoconstriction in the efferent glomerular arteriole?
    A. decrease the volume of urine production due to increased glomeruluar blood pressure
    B. decrease the volume of urine production due to decreased glomeruluar blood pressure
    C. increase the volume of urine production due to decreased glomeruluar blood pressure
    D. increase the volume of urine production due to increased glomeruluar blood pressure
    • First, some terminology: efferent refers to something going downstream/away from a
    • point of interest while afferent refers to something coming in from upstream/toward a point of interest. Since we're looking at the
    • glomerulus, the efferent arteriole would be downstream and a vasoconstriction would increase the blood pressure in the glomerulus. This would, in turn, increase the filtration rate in the glomerulus and
    • thus increase the volume of urine production, making (D) the correct answer.
  6. Inthe reaction below, hydrogen peroxide acts as the limiting reagent. If 680 grams of hydrogen peroxide are reacted, how many grams of water are produced?
    IO3- + 2H2O2 + CH2(COOH)2 + H+ → ICH(COOH)2 + 2O2 + 3H2O

    A. 450 g
    B. 1020 g
    C. 360 g
    D. 540 g
    D. 540 g

    For every two moles of hydrogen peroxide that react, three moles of water will be
    produced. The molar mass of hydrogen peroxide is (1 x 2) + (16 x 2) = 34 g/mol. Therefore 680 grams corresponds to 20 moles of hydrogen peroxide. This would produce 30 moles of water which has a molar mass of 18 g/mol, making the total water produced equal to 540 g.
    (this multiple choice question has been scrambled)
  7. The fluid released by the glomerulus into the Bowman's capsule is essentially identical to which of the following?
    A. virterous humor
    B. interstitial fluid
    C. urine
    D. synovial fluid
    B. interstitial fluid

    Urine is the concentrated result of the fluid released into the Bowman's capsule, but
    the two have very different osmolarities and ionic compositions, making(B) incorrect. Vitreous humor, or the fluid/gel found in theeye, is a specific gel-like composition that is nonidentical the fluid in questionand is far more viscous, making (C) incorrect. Synovial fluid, much like the vitreous humor, has very specialized function and composition
    that is different from the fluid in question, making (D) incorrect. The fluid that the glomerulus releases to the Bowman's capsule is forced outof the capillaries in the same way that fluid is forced out of the capillaries in other tissues. In those other tissues, the interstitial fluid is recycled via the lymphatic system, but in the nephron the fluid is captured, concentrated, and excreted as urine. This makes (A) the correct answer.
    (this multiple choice question has been scrambled)
  8. A particular nitrogen oxide is comprised of 64% N by mass. Which of the following is a possible empirical formula for the oxide?
    A. NO2
    B. N2O3
    C. NO
    D. N2O
    D. N2O

    To answer thisquestion, assume that there is 100 g of the oxide, of which 64 g is N and 36 g is O. Converting these masses to moles, we have N = 64/14 = 4.5and O = 36/16 = 2.25 moles. The mole ratio of N to O is 2:1. Hence, thecorrect empirical formula would be (B) N2O.
    (this multiple choice question has been scrambled)
  9. Which of the following innervate voluntary muscles in the arms?
    A. sympathetic neurons
    B. parasympathetic neurons
    C. ganglionic neurons
    D. somatic neuron
    D. somatic neuron

    parasympathetic and sympathetic nervous systems are part of the
    autonomic nervous system and do not regulate consciously-controlled
    functions. These functions include regulation of heart rate, respiration
    rate, digestion, and arousal. Skeletal muscles are controlled by the
    somatic nervous system which governs consciously-controlled efforts.
    (this multiple choice question has been scrambled)
  10. Superconducting materials can pass current very efficiently and have a resistance of 0 Ω and therefore no voltage can be measured across a superconductor itself even when passing a current. If a superconducting
    wire were connected to a battery, the resistance of the circuit would be:

    A. equal to 0.
    B equal to the voltage of the battery.
    C equal to the internal resistance of the battery.
    D undefined; the battery cannot pass current through the superconductor.
    • Since we are
    • being asked about the resistance of the circuit and V ≠ R, we can
    • immediately eliminate (B). While the resistance of the superconductor
    • itself may be zero, this does not preclude a circuit to which the
    • superconductor is connected from having a resistance. Batteries have an
    • internal resistance which adds to the resistance of the circuits they
    • are in. Therefore the resistance of the circuit overall would simply be
    • equal to the internal resistance of the battery.
    • C equal to the internal resistance of the battery.

    • The superconductor would not be able to negate the battery's internal resistance and
    • therefore (A) is incorrect. (D) is incorrect because we are told that superconductors are able to pass current.
  11. Which of the following statements is FALSE regarding the primary and secondary amines?
    A. Primary amines are in general stronger bases than secondary amines.
    B. Primary and secondary amines both have a lone pair of electrons on the nitrogen atom.
    C. Primary amines are less sterically hindered than secondary amines.
    D. Primary and secondary amines can both be used in the production of an amide.
    A. Primary amines are in general stronger bases than secondary amines.

    Alkyl groups in general electron-density donating and will stabilize a positive charge on nitrogen, making secondary amines stronger bases than primary amines, in general. This makes (A) false and therefore the correct answer. (B) is true because primary amines have only one alkyl group
    whereas secondary amines have two. (C) is true because only quaternary ammonium cations will not have a lone pair of electrons. (D) is true because amides can be produced from either type of amine when reacted
    with a carboxylic acid.
    (this multiple choice question has been scrambled)
  12. Which of the following is FALSE regarding enzymes?
    A. Decreasing the substrate decreases the reaction rate.
    B. Removal of an enzyme cofactor reduces the ability of the enzyme to catalyze the reaction.
    C. The presence of a competitive inhibitor will not affect the vmax of the reaction.
    D. An increase in the substrate concentration will increase the value of vmax.
    • Although the reaction rate (v) is dependent upon the substrate concentration, the vmax is independent of the substrate concentration.
    • That is, the vmax refers to the maximum rate at which a reaction can happen; it does not
    • rely on the rate at which a reaction is actually occurring at any given point in time or substrate concentration (think of it as a speed limit; the speed limit doesn't change depending on how fast you're driving). Therefore, while an increase in substrate concentration would increase the reaction rate (only up to the vmax), the vmax is a speed limit that substrate concentration cannot break (note that other methods for
    • increasing vmax exist that are beyond the scope of this question).
  13. In a community containing several different cultures, a medical practitioner notes that Culture A is high in fatalism (pre-determined
    fate). Culture B practices traditional medicine. Which of the following adequately describe medical concerns during treatment of disease in these cultures?
    I. Culture B may use remedies which interfere with prescribed medications
    II. Culture A may not adhere well to treatment schedules
    III. Culture A and B may both seek out physicians more than needed
    IV. Culture A and B may both seek out physicians at later illness stages than other cultures

    A. I and III
    B. II and III
    C. III and IV
    D. I and II
    • A culture (like Culture A) which is high in fatalism may assume that since fate is
    • pre-determined, taking a medication in a manner consistent with physician instructions is not relevant as it does not affect the end
    • result. This would make the list member numbered roman numeral II correct. A culture (like Culture B) which uses traditional medicine may inadvertently use bioactive remedies which interfere with prescribed
    • medications. Thus it is important to inquire about what traditional medicine is being practiced when working with a culture like Culture B. This makes the list member numbered as II also correct. Both cultures
    • are unlikely to seek out physicians more than needed (especially Culture A, as a belief in pre-determined fate makes one less likely to seek out treatment in general) and are more likely to seek out treatment at later illness stages (Culture B because often cultures that practice traditional medicine will attempt to cure illness with it before turningto modern medicine, and Culture A because fatalism leads patients to wait for fate to run its course before seeking medical assistance).
    • Thus, option (D) is correct.
  14. For the pH of a solution to be estimated accurately using only the concentration of the acid present, which of the following must be true?

    A. The Ka of the acid is very high.
    B. The concentration of H+ must equal the concentration of the conjugate base A-.
    C. The acid must be a weak acid; the pH of strong acids cannot be calculated directly in this way.
    D. The acid must be concentrated; the estimation does not work at high dilution.
    • pH is calculated through -log([H+]), which means the only way the pH of a solution can be accurately estimated from the concentration of the acid is if the acid itself
    • dissociates almost entirely (i.e. has a high Ka value). This makes (A) the correct answer. For weak acids, the Ka is low and little of the acid dissociates, meaning the pH cannot be calculated without knowing the pKa or Ka. This makes (C) incorrect. (B) simply describes when the pH = pKa which is not required to be able to estimate the pH. (D) is incorrect because the pH of strong acids can be estimated for most concentrations and is actually more difficult to estimate at very high concentrations.
  15. A molecule is discovered which blocks production of TSH from the anterior pituitary. What effect would this have in the body?
    A Decrease prolactin release
    B Increase thyroid stimulation
    C Stop ovulation in women
    D Decrease metabolism
    D Decrease metabolism

    TSH is the hormone which stimulates the thyroid gland to release thyroid hormone. Thyroid hormone is responsible for many different effects in the body, one of which is increasing metabolism. Thus decreasing TSH production would decrease thyroid hormone and thus decrease metabolism.
  16. Which of the following gases would tend to be least ideal?
    A. HCOOH
    B. H2
    C. Ne
    D. CH4

    • Gases are more ideal when they are small and exhibit less intermolecular forces. H2 is very small and nonpolar and will be relatively idea. Ne is also nonpolar and relatively small, as is CH4. Formic acid (HCOOH) can form strong dimers through hydrogen bonding
    • (like many carboxylic acids) and these intermolecular forces will make it a very nonideal gas.
  17. An individual with blood type O produces no A or B antigen on their red blood cells. This individual can receive blood from which of the
    A. A, B, AB, and O
    B. A and B only
    C. AB and O only
    D. O only
    D. O only

    For someone who does not produce A or B antigen, the immune system will recognize
    any blood cells that have the A antigen or B antigen or both. Therefore individuals with blood type O can only receive blood from other individuals with blood type O.
    (this multiple choice question has been scrambled)
  18. Johnis driving in his car and is cut off by another driver. He immediately yells at the other car and calls the driver horrible and immoral. John is displaying which of the following?
    A. Interpersonal bias
    B. Fundamental Attribution Error
    C. Stereotype threat
    D. Self-fulfilling prophecy
    B. Fundamental Attribution Error

    Fundamental attribution error is when one attributes behavior more to personality than situation. Option (A) is incorrect; self-fulfilling prophecy refers to a belief that influences behavior to create a result resembling the
    original belief. Option (C) is incorrect; stereotypes are not mentioned in the question. Option (D) is incorrect;interpersonal bias is not a psychological or sociological term.
    (this multiple choice question has been scrambled)
  19. Consider the following scenario: Mary and her boyfriend are driving towards a restaurant for dinner. As they pull into the driveway, Mary
    looks up at the neon sign. Her boyfriend remarks that he cannot read the sign, because it is missing several letters. Mary takes one look and says "it's called Da Vinci's Pizza Kitchen". Mary's observation is an
    example of which of the following:
    Please click on the correct answer:
    A Bottom-up processing
    B Top-down processing
    C Principle of Simplicity
    D Principle of Proximity
    B Top-down processing

    • Option (B) is correct is correct because top-down processing implies the use of prior
    • knowledge to draw a conclusion. Mary used her knowledge of the way letters were arranged to read the name of the restaurant. Option (A) is incorrect, because bottom-up processing would imply an analysis of each
    • individual element. Options (C) and (D) are incorrect, because both are examples of heuristic principles that do not apply to understanding the meaning of the sign. Options (C) and (D) refer to the way objects are grouped.
  20. Which of the following is an example of an application of symbolic interactionism?
    A. Nate smokes a cigarette with his friends, despite the objective evidence that smoking is harmful.
    B.The government to raise the minimum wage to help families earn more money.
    The families spend more money and improve the economy. The improved economy and increased earnings mean larger tax revenue.
    C. An executive at a technology company lowers the pay of his workers the most possible, so that he can earn the most profit.
    D. Members of society work together to improve the lives of everyone
    • Option (B) is incorrect; it is an example of the functionalist approach to sociology. This is a macro-level approach that defines the purpose of elements of society. Option (C) is incorrect because the employer-employee dynamic is a classic example of the conflict perspective. Option (D) is incorrect because the cohesion of society is a requirement of
    • functionalism, not an example of symbolic interactionism. Option (A) is the correct answer because symbolic interactionism is a micro-level approach that explains society based upon social identities and interactions. This is an example of behavior explained by a social dynamic.
  21. Which of the following, if true, casts doubt on the assertion that tryptophan in turkey meat is responsible for induction of drowsiness after consumption?
    A. Other commonly-consumed meats like chicken and pork have higher concentrations of tryptophan than turkey.
    B. Large meals containing high amounts of turkey meat but lacking high amounts of carbohydrates do not induce drowsiness.
    C. Large meals containing high amounts of carbohydrates but lacking turkey meat induce drowsiness.
    D. Consumption of pure tryptophan causes drowsiness.
    • (A) is incorrect because the observation that other meats contain higher concentrations of tryptophan does not mean that consumption of those meats does not also cause drowsiness. Since we are not told how those
    • meats affect drowsiness, knowing they have higher tryptophan concentrations does not mitigate the possibility that turkey also causes drowsiness.
    • (C) is incorrect for similar reasons as (A). Just because carbohydrates cause drowsiness does not mean that turkey does not also cause drowsiness.
    • (D) would strengthen the support for tryptophan causing drowsiness, not cast doubt upon it.
    • (B) is the correct answer because it demonstrates the fact that despite consumption of large amounts of tryptophan, drowsiness is not induced. This casts doubt on the assertion that tryptophan induces drowsiness.
  22. In sickle cell disease, homozygous individuals present with the disease (production of abnormal hemoglobin) while heterozygotes are almost invariably asymptomatic, although they will produce normal as well as abnormal hemoglobin. This suggests which of the following about sickle cell disease?
    A. Sickle cell disease operates under complete dominance.
    B. Sickle cell disease operates under incomplete dominance.
    C. Sickle cell disease operates under codominance.
    D. Sickle cell disease is a sex-linked trait.
    Traits where both versions are expressed (normal + abnormal) are called codominant (making C the correct answer). Another example of a codominant trait is blood type. Incomplete dominance would be the presentation of an intermediate trait which is not the case when two distinct cell types are formed. Complete dominance would be the production of normal blood cells only. Since we lack information about the inheritance patterns of men vs. women for sickle cell disease, we lack sufficient information to say that it will be a sex-linked trait.
  23. Increased steric hindrance enhances the rate of SN1 reactions versus SN2 reactions because
    A. it is more difficult for the nucleophile to attack a sterically-hindered molecule.
    B. steric hindrance increases reactivity which makes SN1 reactions more likely.
    C. steric hindrance protects the nucleophile from reacting with the solvent.
    D. nucleophilic attack of sterically-hindered molecules is easier than non-sterically-hindered molecules.
    • Reactions can be driven towards SN1 or SN2 mechanisms by altering a number of  characteristics. Steric hindrance will prevent the attack of a nucleophile since it will be unable to access its target atom. More
    • sterically-hindered molecules are usually more highly-substituted which makes their carbocations more stable, and more likely to proceed via SN1
  24. Considering socialization theory, which of the following could not explain why an individual comes to believe that he should be competitive?
    A. Parental advice
    B. Themes within film
    C. Genetics
    D. Playing sports with friends
    • Options (A), (B) and (D) are all related to socialization. Family, media and peers
    • are common agents of socialization. Option (C) is correct because genetics is not an agent of socialization.
  25. A patient with decreased production of surfactant in the alveoli would most likely exhibit which of the following symptoms?
    A. Difficulty breathing due to increased tension in the lungs.
    B. Increased air flow to the lungs.
    C. Atrophy of the diaphragm.
    D. Increased systemic blood pressure.
    • A reduction in the alveolar surfactant would increase the surface tension in the alveoli and make breathing more difficult and lung collapse more likely. This is because the surface tension in the alveoli would put pressure on them to close, making (B) incorrect. (C) would not be expected,
    • particularly since the individual's diaphragm would be doing more work, not less. (D) is incorrect because we cannot make a conclusion about how systemic blood pressure would be affected knowing only about pulmonary circulation.