AAMC MCAT test 6r a

MCAT Practice Test 6R Solutions đ Solutions 6R www.PrincetonReview.com MCAT MEDICAL COLLEGE ADMISSION TEST MCAT P RACTICE T EST 6R S OLUTIONS Edited, produced, typeset, and illustrated by Steven A Leduc National Director of MCAT Research, Production & Development, The Princeton Review Jennifer Wooddell Verbal Reasoning Solutions Steven A Leduc Physics and General Chemistry Solutions Judene Wright Biology Solutions Douglas S Daniels Organic Chemistry Solutions Copyright â 2003, 2002 by Princeton Review, Inc All rights reserved MCAT is a service mark of the Association of American Medical Colleges (AAMC) TPR is not affiliated with Princeton University or with the AAMC Version 1.0 www.PrincetonReview.com MCAT P RACTICE T EST 6R S OLUTIONS C ONTENTS : Physical Sciences Verbal Reasoning 12 Biological Sciences 30 030316 PHYSICAL SCIENCES Passage I D Which of the four compounds listed in the choices would produce a basic (alkaline) solution in a lake? Since KOH (choice D) is a strong base, its dissolution in water would produce a basic solution, so this is the best choice Choice C, sulfuric acid, would produce an acidic solution, while neither choice A nor B would affect the pH C A hydrogen bond is the intermolecular force between the partial positive charge on an H bonded to an F, O, or N atom and the partial negative charge on an F, O, or N atom in another molecule Methane (CH4) has no F, O, or N atoms, and carbon dioxide (CO2) has no H atoms, so if were asked for the pair of compounds that can form extensive networks of hydrogen bonds with both participating, we must eliminate choices A and B (which involve methane) and choice D (which involves carbon dioxide) D Isotopes of an element differ only in the number of neutrons they contain, not the number of protons; this eliminates choices A and B right away Carbon-12 has protons and neutrons, while carbon-14 has protons and neutrons Therefore, these isotopes differ by = neutrons, choice D C Since HCl is a strong acid, it will dissociate completely in solution So, if [HCl] = 0.01 M, then [H+] = 0.01 M, and pH = log [H+] = log (0.01) = log (102) = (2) = D Here are the geometric families and shapes of the given molecule, methane, as well as those of the four choices: H C H H H S H H O C O CH4 geometric family: tetrahedral shape: tetrahedral H 2S geometric family: tetrahedral shape: bent F F Xe F F Cl CO geometric family: linear shape: linear Si Cl Cl Cl XeF4 geometric family: octahedral shape: square planar SiCl geometric family: tetrahedral shape: tetrahedral While both H2S and SiCl4 are in the same geometric family as methane, H2S has a bent shape while SiCl4 has a tetrahedral shape Therefore, of the choices given, SiCl4 (choice D) is most like CH4, and thus the best choice here B In a very low pH environment, the amino group of glycine, H2NCH2COOH, is protonated (as is the carboxyl group), giving H3N+CH2COOH, choice B A Helium (choice B) is an inert gas and does not accept electrons H2 (choice C) is a stable molecule and is therefore unlikely to accept electrons Iron (choice D) is a metal and is therefore far more likely to donate electrons (becoming a cation) than to accept them However, sulfur (choice A) is in the oxygen family (Like oxygen atoms ) and has a high electron affinity, so its the best choice here Passage II Note: The questions in this passage are on periodic trends or atomic structure The passage text is irrelevant A Atomic radius generally decreases as we move down a column or across a row to the right in the periodic table The four atoms listed as choices are all in the same row (Period 3), and sodium (choice A) is farthest to the left, so we would predict that it has the largest radius of the four D Ionization energy generally increases as we move up a column or across a row to the right in the periodic table The four atoms listed as choices are all in the same row (Period 4), and krypton (choice D) is farthest to the right, so we would predict that it has the highest ionization energy of the four Furthermore, since krypton is a noble gas, it has the particularly stable octet configuration and thus a very high ionization energy 10 C Since strontium (Sr) has atomic number 38, a (neutral) strontium atom has 38 electrons Since the total number of protons and neutrons in strontium-90 is 90, the sum of the numbers of protons, neutrons, and electrons is 90 + 38 = 128 11 B Bromine (Br) has atomic number 35, which means that every bromine atom contains 35 protons If an isotope of bromine has 44 neutrons, then the total number of protons and neutronswhich is the mass numberis 35 + 44 = 79 12 C Electronegativity generally increases as we move across a row to the right in the periodic table As a result, bonds between atoms on the far left with those on the far right (excluding those in Group 18, the noble gases) tend to be highly polar (ionic) Of the four pairs listed as choices, Ca (calcium) and I (iodine) are farthest apartCa is in Group 2, I in Group 17and would therefore be the most likely to form an ionic bond Passage III 13 B Using distance = rate Ơ time, we get d = (3 Ơ 108 m/s) Ơ (7 Ơ 102 s) = 21 Ơ 106 m = 2.1 Ơ 107 m 14 D Any object moving in a circular path must feel a force that provides the centripetal force (choice D) For a satellite orbiting the earth, it is Earths gravitational force that provides the necessary centripetal force Choice A is wrong because centrifugal force is a fictitious force directed away from the center of the circle and does not keep an object moving in a circular path Choice B can be eliminated since, for one thing, at the altitude of the GPS satellites, there is no atmosphere And we can eliminate choice C, since the earths gravitational force on the satellite is much stronger than the moons (so it doesnt offset it) 15 A This is a proportion question using Newtons Law of Gravitation, F = GMm/r2 If we increase r by a factor of and m by a factor of 4, the ratio m/r2 will change by a factor of 4/62 = 1/9, so F will decrease by a factor of 9: FÂ = G M (4 m) Mm Mm G = G = F = 36 9 (6r ) r r 16 C The passage tells us that the voltage of the NiCd battery is 1.32 V Since we know V and were given P (the power), we use the equation P = IV to determine the current: I = P/V = (3.96 W)/(1.32 V) = A 17 C The last sentence of the passage tells us the two frequencies that are used: f1 = 102.1 MHz and f2 = 104.9 MHz By definition, the beat frequency is the difference between the two: fbeat = f2 f1 = 2.8 MHz = 2.8 Ơ 106 Hz 18 D The speed of an electromagnetic wave through a medium is given by the equation v = c/n, where n is the mediums index of refraction The vacuum of space has n = 1, so v = c; however, through any material medium (such as atmospheric gases), n is greater than 1, so v will be less than c 19 A Were told in the first line of the second paragraph of the passage that the radioactive cesium source has a mass of grams So, the question is, How many half-lives must elapse to get this mass down to 0.625 grams? Dividing grams by repeatedly until we reach 0.625 grams, we see that it takes half-lives: half-life 2nd half-life 3rd half-life g ổ ổổổặ 2.5 g ổ ổổổ ổặ 1.25 g ổ ổổổ ổặ 0.625 g Since each half-life is 175 years, the time period required would be Ơ (175 years) = 525 years Passage IV 20 C The second sentence of the passage states that the synthesis of Olestra starts with a base-catalyzed cleavage (emphasis added) Of the choices given, only choice C, NaOH, is a base 21 C Since the specific heat of water is cal/gCor, equivalently, kcal/kgCthe fact that the temperature of kg of water increased by 50C means that the energy added to the water was 50 kcal: ấ kcal q = mcDT = (1 kg) (50C) = 50 kcal ậ kg C So, if the combustion of 10 peanuts releases 50 kcal of energy, the combustion of peanut would release 50/10 = kcal 22 A In the last sentence of the third paragraph of the passage, we learn that Olestra is not metabolized . If its not metabolized, it wont contribute any dietary calories to a human consumer 23 A From the structure of glycerine shown in Figure in the passage, we see that this molecule contains OH groups, while the formula given in the question tells us that isopropyl alcohol contains just OH group Therefore, not only does glycerine have a greater molecular weight, but it will have far more hydrogen bonds than isopropyl alcohol As a result, the boiling point of glycerine should be much higher than that of isopropyl alcohol (choices C and D are eliminated, and A is a better choice than B) [By the way, the BP of glycerine is 290C, while the BP of isopropyl alcohol is just 82.5C.] 24 B First, eliminate choices C and D A mere 20 moles of methanol will not weigh several hundred thousand (and certainly not more than a million) pounds! The molecular weight of methanol, CH3OH, is 12 + 3ã1 + 16 + = 32 g/mol Therefore, 20 moles of CH3OH has a mass of (20 mol)(32 g/mol) = 640 g, or 0.64 kg Since the last sentence of the passage tells us that kg equals 2.2 pounds, we find that 0.64 kg is equivalent to (0.64 kg)(2.2 lb/kg) ê (0.7)(2) = 1.4 lb Independent Questions 25 B Electron affinity generally increases as we move to the right across a row or up within a column in the periodic table Of the atoms listed as choices, fluorine (choice B) is farthest to the right and highest in the periodic table, so wed expect that it would have the highest electron affinity (Furthermore, if F acquires an extra electron, it achieves the much-desired noble gas (octet) configuration, so F really wants an extra electron; therefore, it has a high electron affinity.) 26 C The half-cell reduction reaction of copper is shown directly in the table, Cu+ + e ặ Cu, with E = +0.52 V If copper is to be reduced, then the other metal used in the cell must be oxidized, and we must remember that to form a galvanic cell, we need the overall cell voltage to be positive The oxidation of silver has a potential of 0.80 V (the reverse of the reduction of Ag+ given in the table), so the overall cell voltage here would be 0.28 V, and silver is eliminated from consideration (and so choices A and D are wrong) Note that we dont need to check lead (because its in both of the remaining choices, B and C) Since the oxidation of zinc has a potential of +0.76 V (the reverse of the reduction of Zn2+ given in the table), the overall cell voltage here would be +1.38 V, so zinc will work Therefore, the answer must be C 27 A Frequency ( f, the number of cycles per second) and period (T, the number of seconds per cycle) are reciprocals of each other Since f = 1/T, we have f T = 28 A Use Big Five #2, and call down the positive direction Then v0 = v (its negative, because v0 is upward and were calling down the positive direction) and vfinal = +v, so vfinal = v0 + at becomes v = (v) + gt, or 2v = gt, which gives t = 2v/g This means that t is inversely proportional to g So, if g is decreased by a factor of 6, then t will increase by a factor of Passage V 29 C In the reaction Ag + H2S ặ Ag2S + H2, the Ag displaced H from H2S and took its place, forming Ag2S This is an example of a single replacement (or single displacement) reaction 30 A By the stoichiometry of Equation (which is balanced), moles of SO42 ions would produce moles of H2S Since the molar masses of H and S are and 32, respectively, each mole of H2S has a mass of 2ã1 + 32 = 34 g, so the mass of moles of H2S is ã 34 g = 68 g 31 B Because H2S is a weak acid (as stated in the sentence above Equation in the passage), its ionization constant, Ka, is small Since most weak acids have Ka values in the range 1012 to 102, wed certainly expect that the Ka value of H2S is in this range as well, and thus be much less than (Granted its small, so we could say that its near zero, but the fact that Ka values can actually be measured and used in calculations means that we wouldnt say that all weak acids have ionization constants that are negligible (i.e., near zero); wed instead simply say that theyre very small So, A is a good choice, but B is a better choice here.) 32 B Choices A and D are not reactions between the two compounds; instead, they show how the ions would react to form each compound separately; these choices can therefore be eliminated Only choices B and C show the ion from one compound reacting with the opposite ion from the other compound Choice B shows the reaction that forms the insoluble CaCO3, which crystallize[s], encapsulating coins, sand, and decaying matter into rock-like clumps [which is what] the explorers who discovered the treasure [in the ocean near Cuba] found , as mentioned in the passage This is the best choice here Choice C shows the formation of NaCl(s), which we know is soluble, especially since the passage talks about finding treasure in the ocean, where NaCl would be dissolved into its separate ions 33 D Lets see how the oxidation numbers of the atoms change as a result of the reaction: oxidation numbers: +1 +1 2 Ag(s) + H2S(aq) ặ Ag2S(s) + H2(g) Since Ag was oxidized (its oxidation number increased), it acted as the reducing agent Passage VI 34 D We learn in the second-to-last sentence of the first paragraph of the passage that tones separated by a perfect fifth differ in frequency by a factor of 2/3 This means that the higher-frequency tone has a frequency that is 3/2 times the lowerfrequency tone when the tones are separated by a perfect fifth Since the equation given in the passage tells us that f is proportional to T1/2 (where T is the tension in the string), if we want to increase f by a factor of 3/2, then we have to increase T by a factor of (3/2)2, which is 9/4 35 C According to the equation given in the passage, f = (T/r)1/2/(2L), we can lower f by lowering the strings tension T, increasing the strings linear mass density r, or increasing the strings length L Of the choices given, only C (using heavier stringsthat is, strings with a greater linear mass density r) corresponds to one of these options 36 D In the last paragraph, the passage states that the best violins produce loud tones over the full frequency range of the instrument (emphasis added) Each string has a characteristic fundamental frequency, so in order to produce loud tones over the instruments full frequency range, wed want the violin to have good resonance at the fundamental frequencies of all the strings 37 B In the second paragraph of the passage, we learn that the A string of the violin or viola has a frequency of 440 Hz, and that the cello is tuned one octave below the viola, which means the frequencies of the cello strings are half that of the viola strings. So, if the A string of the viola is tuned to 440 Hz, the A string of the cello is tuned to 12 (440 Hz) = 220 Hz 38 D In the second paragraph of the passage, we learn that the A string of the violin has a frequency of 440 Hz, so a list of the four fundamental frequencies of the violin must include 440 Hz This eliminates choices A and B We also learn that the violins strings are tuned with decreasing frequency to the notes E, A, D, G So, if A is 440 Hz, then E must be greater than 440 Hz Only choice D includes a frequency higher than 440 Hz Passage VII 39 B The atom is attached to springs, each of force constant K When an atom displaced a distance x from its equilibrium position, each spring exerts a force of magnitude K x , so the magnitude of the total force on the atom is 2K x This means that the effective spring constant for this system is 2K 40 D Frequency ( f, the number of cycles per second) and period (T, the number of seconds per cycle) are reciprocalsor inversesof each other 41 C The question tells us to use a dimensional argument to identify the correct formula for T in terms of K and M This means that all we need to check is that the dimensions (or units) of the two sides of the equation match The left-hand side of each equation in the answer choices has units of seconds2, since the period T is measured in seconds and p is a constant Therefore, we need to determine which right-hand side also has units of seconds2 From the equation F = K x , we know that the units of K are N/m, which is the same as kg/s2 So, to get s2 out of this, we need to flip Kto get s2/kg and then multiply by kg (mass) Therefore, the right-hand side of the equation must contain the term (1/K)ãM, or M/K Only choice C contains this term 42 A For an oscillatory system without dissipative effects due to friction, the total mechanical energy, E, is conserved As the oscillator moves, there is a continuous trade-off between kinetic and potential energy The kinetic energy and the potential change individually, but their sum, E = KE + PE, remains constant (choice A) Note that momentum is constantly changing since the speed and direction of the oscillator are constantly changing 43 D In the first line of the second paragraph of the passage, were given the formula for the potential energy of a spring: PE = Kx2/2 Since there are springs here, the potential energy will be Kx2/2 + Kx2/2 = Kx2 When the atom is at its greatest distance from equilibriumthat is, when x = A, where A is the amplitudethere is no kinetic energy, only potential energy Therefore, E = KE + PE = + KA2 = KA2 Solving the equation E = KA2 for K, we get K = E/A2 (choice D) We could have also answered this question by just using a dimensional argument, like in Question 41 above Since [E] = J = Nãm, and [K] = N/m, wed need to divide Nãm by m2 to get N/m That is, wed have to divide E by A2 to get K, so the answer must be D 44 B From the equation q = mcDT, where q is heat (energy), m is mass, c is specific heat, and DT is the temperature change, we find that c = q/(mDT), so [c ] = [q ] J = [ m ][ DT ] kg K 45 A The first sentences of the passage say, let us assume that each atom can oscillate about its equilibrium position Interactions with neighboring atoms hold it in place . Therefore, the model described is limited by this assumption, which holds very well for solids However, we know that the particles of a monatomic gas move very freely; they are not restricted to small oscillations around fixed equilibrium positions established by interactions with neighboring particles (In fact, in the kineticmolecular theory of ideal gases, we assume that there are no such interactions.) Since the basic assumption of the model fails for gases, it cant be used to describe gases Passage VIII 46 B Compound contains a four-membered ring, while Compound contains a six-membered ring, so their structural formulas are clearly different Also, Compound contains Bs, Ps, Hs, and NR2 groups, while Compound contains Bs, Ps, Hs, and NR2 groups, so their molecular formulas are different, too: B2P2H2(NR2)2 vs B3P3H3(NR2)3 However, their empirical formulaswhich give the smallest whole numbers that specify the correct ratios of the atomsare the same: BPHNR2 47 C From the stoichiometry of Equation 1a (which we assume is balanced), the given initial amounts of reactants will produce 0.003 mol of PH3(g) Since the volume of mole of gas at STP (0C and atm) is 22.4 L, the volume of 0.003 mol of gas at STP will be (0.003)(22.4 L) = (3 Ơ 103)(22.4 L) = (3 Ơ 22.4)(103 L) = 67.2 mL 48 A Choices B and C are identical, so both can be eliminated Now, since a phosphorus (P) atom has valence electrons, not 7, the answer must be A, not D 49 A From the Ideal-Gas law, PV = nRT, we know that V = (nR/P)T, so a graph of V vs T should be a straight line with slope nR/P, which is always positive (This eliminates choice D, by the way.) If the pressure P is a constant, then the slope is proportional to n, the number of moles in the sample Both samples have a mass of gram, but Compound has a greater molar mass than Compound (1.5 times as much, to be specific) Therefore, the value of n for the Compound-2 sample is lower than the value of n for the Compound-1 sample As a result, the V vs T graph for Compound will have a smaller slope than the one shown for Compound 1, and would thus appear below the plot for Compound [Note: The graph of P vs T for any ideal gas is a straight line that would intersect the T axis at a common point: 273.15 C; that is, at absolute zero (0 K) For the graphic shown with the question, the unit on the T axis is kelvins, so the lines would all intersect the T axis at the origin In either case, a line with a smaller slope must appear below a line with a greater slope.] P P greater slope greater slope smaller slope 273.15 smaller slope T (C) T (K) Independent Questions 50 A The term isoelectronic means same number of electrons Because a neon atom has 10 electrons, the question is asking for the atom or ion that doesnt have 10 electrons The answer is A, helium (since it has only electrons) 51 D The work W required to lift an object of mass m through a vertical distance h in a uniform gravitational field is given by the expression mgh, the product of the gravitational force, mg (which wed have to provide to lift the object) and the distance, h Therefore, W is proportional to h, which implies that if h is doubled, then so is W 52 A By Grahams law of effusion, we know that lighter gases diffuse faster than heavier ones Because Gas X has a lower density than Gas Y (at, we assume, the same pressure and temperature), the molecules of Gas X must be less massive than those of Gas Y Therefore, Gas X will diffuse faster, because it has a lower molar mass than Gas Y 53 B A catalyst has no effect on a reaction at equilibrium, so the amount of ammonia at equilibrium with a catalyst will be the same as the amount of ammonia at equilibrium without a catalyst 54 D A body is in translational equilibrium if the sum of the external forces on it is zero A body is in rotational equilibrium if the sum of the external torques on it is zero (And a body is said to be simply in equilibrium if its in both translational and rotational equilibrium.) Passage IX 55 C Imagine a rocket floating in free space If its engines are ignited, causing chemical reactions that expel exhaust gases, the rocket will accelerate in the opposite direction We can view this as a consequence of Conservation of Momentum The system originally had zero momentum; if part of the system then moves in one direction, the other part of the system must move in the opposite direction so that these two oppositely-directed momenta add up to zero But we can also view this as a result of Newtons Third law (to every action, there is an equal but opposite reaction) The rocket exerts a force expelling the gases, and the gases thus exert a reaction force, in the opposite direction, on the rocket The same is true for a comet expelling gas as a result of sublimation of some of its frozen solids, so choice C is the best choice Choice A can be eliminated since Newtons First law tells us what happens in the absence of a net force; it wouldnt account for the production of a force Choice B can also be eliminated; Newtons Second law will tell us how the comet will react to any force (including the perturbing force), but it doesnt account for the perturbing force And, finally, choice D is eliminated since the third sentence of the second paragraph of the passage specifically tells us that the deviations in the orbits of comets (caused by the perturbing force) are nongravitational 56 C The passage states that the sublimation of the frozen solids in a comets nucleus is caused by sunlight warming its surface As the comet orbits the sun, only the portion of the surface facing the sun receives sunlight As a result, gases are ejected from the side of the nucleus facing the sun, which causes the reaction forcewhich acts in the direction opposite to the direction of the expelled gases to be exerted on the nucleus in the direction away from the sun comet nucleus reaction force (away from the sun) 57 B According to a typical phase diagram, solids can sublime only in conditions of low pressure (specifically, below the pressure at the triple point) Therefore, choice B is best SUN gases P solid vapor T 58 A Choices B, C, and D are all false, so the answer must be A A (frozen) solid is held together by relatively strong intermolecular forces A pile of rocks, on the other hand, would be held together only by the gravitational force, which is much weaker So, when the rock pile comet strikes the gas molecules in the atmosphere of Jupiter, the collisions will be much more effective at breaking up a rock-pile nucleus than they would be if the nucleus were a single solid piece (of frozen compounds) 59 B As stated in the last paragraph of the passage, Comets become visible to the unaided eye when the coma forms and extends into a vast, long tail of gas and dust. We therefore eliminate choice D (While ices can reflect light, theyre in the nucleus, which is concealed by the surrounding cloud of dust particles and gas, as stated in the second sentence of the first paragraph of the passage.) So, how we choose among choices A, B, and C? One way is to realize that two of these choices mention gas, while only one mentions dust Since there cant be two correct answers, wed be led to eliminate the two that mention gas, and thus select choice B Another way is to realize that diffuse gases are very poor reflectors of light (for example, we dont wear sunglasses because sunlight is reflecting off air molecules; we wear them to help shield our eyes from the reflection of sunlight from solids and liquids, not gases) This observation eliminates choices A and C, so choice B is indeed the best 60 C The two models differ on the question of what the cometary nucleus is made ofis it made of rocks or is it a solid of frozen ices? If we were able to perform a spectroscopic study of the cometary nucleus, wed be able to determine the composition of the nucleus and thus decide between the two models Passage X 61 C From Equation 1, PbI2(s) Pb2+(aq) + I(aq), we have Ksp = [Pb2+][I]2 If S moles of PbI2 dissolve in liter of water, then well have [Pb2+] = S and [I] = 2S Substituting these into the equation for Ksp gives Ksp = (S)(2S)2 = 4S3 62 D By analogy with Equation 1, the dissociation of lead(II) bromide is PbBr2(s) Pb2+(aq) + Br(aq), so Ksp = 2+ 2+ 2+ [Pb ][Br ] With the given initial concentrations of Pb and Br , [Pb ] = 0.0001 M = 104 M and [Br] = 0.00005 M = Ơ 105 M, the initial reaction quotient (or ion product, in this case) is [Pb2+][Br]2 = (104)(5 Ơ 105)2 = 2.5 Ơ 1013 Since this is smaller than the Ksp of lead(II) bromidegiven to be 4.6 Ơ 106 in the last sentence of the passagethere will be no precipitate Choice D is the answer 63 B As given in the last sentence of the paragraph that follows Equation in the passage, the molar solubility of PbI2(s) in water is S = 1.89 Ơ 103 M So, in 100 mL = 0.1 L of a saturated aqueous solution of PbI2, therell be (0.1 L)(1.89 Ơ 103 M) = 1.89 Ơ 104 mol of dissolved lead(II) bromide Since the molecular weight of PbI2 is 207 + 2(127) = 461 g/mol, the mass of PbI2 present in the saturated solution is (461 mol )(1.89 Ơ 10 -4 mol) ê (450 g g -4 mol )(2 Ơ 10 mol) = 900 Ơ 10 -4 g = 0.09 g Therefore, choice B is best 64 A Because the value of Keq (the ratio of products to reactants at equilibrium) for Equation 2, given to be Ơ 1015, is so large, the reaction goes essentially to completion That is, wed say that essentially all (100%) of the reactant I(aq) is consumedin this case, converted to I2(aq) 65 D As shown in the solution to Question 62 above, the expression for the Ksp of lead(II) bromide is [Pb2+][Br]2 Passage XI 66 D The equation F = QE for the electric force on a charge Q says that if Q is positiveas it is in this experiment, since (as stated in the second sentence of the first paragraph of the passage) atoms are ionized by removing electronsthen F is in the same direction as the electric field, E In order to accelerate an object to the right, we need a force F directed to the right, and, thereforesince the objects each carry a positive chargean electric field E thats directed to the right 67 C The superscript in 6Li is the mass number of the atom, which, by definition, is the number of protons plus the number of neutrons (Note that choice A can be eliminated immediately, since a glance back at the periodic table reveals that every lithium (Li) atom contains exactly protons, not 6.) 68 A From the equation given in the passage, we find that v = 2QV M So, if V is decreased, the speed v of every ion will decrease Since the ions are all moving slower, theyll all require more time to reach the detector 69 C Let x be the distance from the right-hand plate to the detector and let V be the voltage between the accelerating plates; these values are fixed The time required for an ion to travel this distance (the flight time) is equal to t= x = v x 2QV M =x M 2QV where weve used the expression for v given in the solution to Question 68 above Since 3H+ and 3He+ have the same M and the same Q, the value of t will be the same for both ions 70 D Because Peaks and are the peaks for singly-ionized isotopes of lithium (emphasis added), as stated in the last sentence of the passage, the peaks for doubly-ionized lithium isotopes wont include Peak or Peak This observation eliminates choices A, B, and C, so the answer must be D [Alternatively, since t = x M 2QV , a greater Q leads to a shorter flight time Therefore, doubly-ionized lithium ions will have shorter flight times than singly-ionized lithium ions So, if Peaks and correspond to singly-ionized lithium, the peaks for doubly-ionized lithium will appear at shorter flight times Only Peaks and in Figure are at shorter flight times than Peaks and 4.] 10 Passage VII 118 B A: While this statement is true according to the author (see lines 28-29), it is too narrow to be the major thesis or main point of the entire passage The main issue for the author is that when self-interested decisions are made by many people on a large scale, it can have a destructive impact on public resources B: Yes The author relates the story of the tragedy of the commons in which, without regulation, each individual herder acts to maximize his or her own good to the detriment of the community as a whole He generalizes from this scenario in the last paragraph to argue that we must abandon the commons assumption. That is, we cannot allow individuals to use public resources for their own benefit while bringing society to universal ruin. His discussion in the first paragraph as well shows that he is speaking in general terms, and that the story of the commons is meant to tell us something about society as a whole C: This choice is too extreme to be supported by the passage; the author states that coercion is defensible only if a majority agree to it (lines 52-54) Even if it were not too extreme, this choice would be too narrow to be the major thesis, as it is only one specific point made in the fifth paragraph D: The author uses the metaphor of the tragedy of the commons, not of the invisible hand (which is discussed in the first paragraph) to illustrate what happens to society when individuals act only in accordance with their own self-interest 119 B A: Remember the main idea of the passage The author doesnt indicate that there is a problem with all self-interested actions, only with those that result in the degradation or destruction of public or collectively held resources (see lines 16-19, 38-46, and 59-62) B: Yes See the explanation for answer choice A C: While the natural environment (mentioned specifically only in line 12) is one (of many) public or collective resources that should be protected through coercion, the author does not single it out as the decisive determining factor D: The author does not describe rational self-interested actions that collectively destroy public resources as immoral For example, acting in accordance with the principle of the invisible hand [prevents] action based on rational analysis (lines 4-8); that is, it is unreasonable or illogical or counterproductive, but it is not described as unethical (be careful not to bring your own opinions or beliefs into play) Furthermore, the author never suggests that common beliefs or attitudes are a valid basis for coercion 120 A Item I: Item II: Item III: Yes National parks would qualify as a public resource, and mandatory fees would be a potentially acceptable (if agreed to by the majority) form of coercion (like taxes) to keep the parks from being destroyed through overuse (see paragraph five) The author proposes restricting access to public resources in order to preserve them for society as a whole, not taking them away from society as a whole by selling them off to individuals Dont forget to use the main idea of the passage for all questions The passage goes in the opposite direction; the author argues for regulating and restricting, not increasing, individual access to and use of public resources This choice is inconsistent with the central theme of the passage 121 A A: Yes According to the author, rational individuals add up the costs and benefits to themselves [the component utilities (lines 31-40)] in order to make decisions, without taking into account the effect on society when all individuals reason in this way Each billboard benefits the individual manufacturer, while the extent to which a single additional billboard lessens the impact the billboards have on consumers is negligible and is spread out among all who have erected them However, when all manufacturers act on this logic and the highways are overcrowded with billboards, each individual billboard is very unlikely to be noticed or to have an effect on people driving by (and may even make them angry because they can no longer enjoy the scenery) A few billboards stand out, but hundreds of them blur together The result is that this form of advertising would then become ineffective for all manufacturers, just as overuse of the commons eventually makes them useless for all of the herders 24 B: Neither the passage nor the question gives us reason to believe that if lots of graduates accept job offers, there will be some harm to society as a whole, to those graduates, or to future graduates No public resource is involved in this choice C: A suburban home is private property, not a public or collectively held resources There is no indication that this use of private property entails any significant costs to others or to society as a whole, and the ones making the decision (the homeowners) are not the ones who most benefit (the children) D: Emission control standards limit access to public resources (in particular our air and water) so that we can all continue to enjoy those resources in the future This is the opposite of the logic of the commons 122 B A: The author presents the tragedy of the commons as a scenario that has already taken place Notice as well the wording used in lines 48-50, where the author writes that as the human population has increased, the commons concept has had to be abandoned. B: Yes In the case of the commons, no restrictions were placed on how or to what extent individuals used the grazing lands, with the tragic results as described The author argues that systems of mutual coercionthat is, regulation of some sortmust be imposed to avoid the destruction of public resources (lines 51-58) Therefore, the author would most likely agree that when resources are regulated, self-interested actions will not necessarily drive us to ruin, and thus that the authors argument would not apply in those cases C: The author argues that the tragedy of the commons occurs when societies become stable (lines 23-27) This choice would contradict, not clarify the authors argument D: While management might be the same as regulation or coercion, it might not be; management does not necessarily restrict how resources may be used Furthermore, there is no reason to believe that management which did qualify as coercionas coercion is discussed in the passage (lines 51-58)would have to be local to be effective Passage VIII 123 B A: The passage does not discuss any individual works of literature B: Yes Throughout the passage, the author explains how formalist critics approach literary analysis In the third paragraph, the passage explains that formalism is concerned only with the work itself, not with how or why that work was written In the fourth and fifth paragraphs, the passage discusses why formalism is not concerned with the specific characteristics of readers and why formalists assume an ideal reader, and then it rejects two different ways of judging a works value Finally, in the last paragraph, the author returns to the idea that a literary work, by formalist standards, cannot be seen simply as the product of the author or through the eyes of its readers C: While the author does specify which part of the authors intent is relevant to formalist criticism [that is, what appears in the work itself (lines 31-34)], this is not the same as detailing a method for measuring an authors intent Even if it were, this choice would still be too narrow to capture the purpose of the author in the passage as a whole D: The author does mention that the study of aspects of literature other than the work itself have value (lines 25-30), but not as part of formalist criticism That is, these undertakings would be defensible as studies, but not as literary criticism, which the author equates with formalist criticism (lines 61-63) In any case, simply describing these alternatives is not the authors primary purpose in writing the passage Dont get trapped by the word defensible in line 41; here the author is defending the formalist approach, not alternatives to it 25 124 C A: This choice is inconsistent with the main idea of the passage The author rejects the idea that the effect on readers is a relevant focus for formalist criticism (lines 25-30, 34-39, and 61-63) B: This choice is inconsistent with the authors description of formalist criticism, and so with the main idea of the passage In lines 19-24, 30-34, and 61-63, the author argues that the formalist critic is not interested in the authors motivation or intent in writing the work C: Yes The author indicates that formalists should focus on the structure of the thing composed (lines 22-24), that is, the work itself (lines 19-20; notice the word primarily in line 20) This themethat criticism deals only with the work itselfruns throughout the passage D: The author argues at the end of the passage that the truth of a works ideas, even if such a thing could be measured, does not define good literature Therefore, we can conclude that the formalist critic would not be concerned with it 125 B Note: Roman numeral I appears in all four answer choices Therefore, you not need to read or evaluate it, as it must be included in the correct answer Item I: Yes The author draws this distinction in lines 31-34 in order to emphasize the claim that formalist criticism does not concern itself with the author, but only with the finished product, that is, the work Item II: Yes The author draws this distinction in order to show that formalist criticism is not concerned with the readers or the different ways in which a work might be interpreted by various readers Item III: These two motivations are listed (lines 10-14) as reasons for which an author might write The passage is not interested in drawing a distinction or contrast between them, but in dismissing them both as irrelevant considerations 126 A A: Yes In lines 50-55, the author (writing as a formalist criticsee the word we in line 54) argues that neither the sincerity of the author nor the critics reaction provides a valid standard by which to measure literary value This theme continues into the last paragraph, where the author claims that good literature is not defined by its causes (the author), its effects (on its readers), or by the truth of its ideas (lines 51-65) Given that the entire passage is a description and defense of formalist criticism, we can assume that the author would consider formalist evaluations to be more valuable B: This choice contradicts the passage Formalist criticism dismisses the authors motivations (lines 10-14, 19-24, 30-34, and 61-63), and the author of the passage believes it to be effective, not ineffective C: The author never defines the characteristics of an ideal reader. In fact, given that this concept is an abstraction used to keep the critics focus on the work itself and to eliminate the actual human readers from the equation, we can infer that an ideal reader would have no distinguishing features or qualities D: This is a negation Take out the word nothing, and you have a direct quote from the passage (lines 63-65) 127 C Note: Each answer choice is a quote or paraphrase from the passage The question asks you to decide which one of these claims is best supported; that is, for which one does the author provide the most evidence? A: The author presents this (lines 14-17) as something that is obviously true, that is, that anyone would obviously know The author does rephrase it by saying that is, that they are recreated in the minds of actual readers, but this does not constitute support for the conclusion itself B: The author presents this claim as being true by definition A literary work is a document, and documents can be analyzed in this way, but if we ask why, there is no answer in the passage C: Yes The author claims that critics must assume an ideal reader because no other approach is possible That is, the author claims that this strategy is defensible (lines 39-41), and then goes on to explicitly defend it (lines 4149) by ruling out the three alternatives D: This claim is asserted as a fact in line 59, with no further evidence or explanation to support it, beyond the statement that no critic would deny its truth (lines 60-61) 26 128 D A: This choice is too extreme The passage states that psychological studies of literature are valuable and necessary (lines 27-29) They just dont qualify as formalist literary criticism B: Read the answer choice carefully It is the formalist critics, not those who apply biographical or psychological studies, who assume that the relevant part of the authors intention is what the author actually put into the work (lines 30-32) C: This choice is too extreme, and it misrepresents the passage in other ways as well The author states that the analysis of the various readings of a work involves delving into psychology and the history of taste (not biography, which is involved in studies focused on the author) (lines 20-22 and 25-28) However, the passage does not also claim the reverse, that is that psychological studies necessarily involve accounting for all possible readings of the work In fact, some psychological studies of literature focus on the author, not the readers (lines 20-22) Finally, the author rejects a psychological approach to literature not because it might account for multiple readings of a work, but because formalist critics believe that the psychology of authors and readers is irrelevant to the task of analyzing the work itself (lines 1924 and 28-38) D: Yes In lines 19-24, the author argues that the mind (psychology) and life (biography) of the author are irrelevant; what is important to the critic is the structure of the work itself 129 C A: The author would disagree with this statement The people involved in the literary transaction would include the author of the work and the works readers, including critics The author of the passage argues that literary criticism that is, formalist criticismis not concerned with the life or intent of the author (lines 10-14, 20-24, 30-34, and 61-63), interpretations on the part of various readers (lines 14-20, 25-30, 34-38, and 61-63), or the strength of critics reactions (lines 54-55) B: The author would disagree with this claim The passage claims that the context, historical or otherwise, in which the work was written is largely irrelevant; what matters is the structure of the work itself (lines 19-24, 25-28, and 56-59) C: Yes This is consistent with the authors argument in lines 30-34, which asserts that the only aspect of an authors intent that is relevant to criticism is that which appears in the work That is, only the finished work itself is important D: The author never states or suggests that what is taught in English departments has any relevance to a definition of literature In fact, the passage offers no such definition, on any basis 130 A A: Yes By rejecting two nonformalist tests of literary value (lines 49-55), in the context of a passage that offers an extensive explanation and defense of formalist criticism, the author suggests that formalist criticism can in fact evaluate the validity of different literary structures (In lines 19-24, the author indicates that the focus of formalist criticism is literary structure.) B: Formalist criticism assumes a standardized ideal reader, and so does not concern itself with differences between readings of a work (lines 34-49) C: Formalist criticism does not focus on differences between authors (lines 19-24) Therefore, we have no reason to believe that it could be used to distinguish between their personalities D: The author, a formalist critic (lines 54-55), suggests that there is no way to tell if rhetoric is in fact effective (lines 6668) 131 B Note: The question does not ask which assertion is supported by the passage (they all are), but instead which claim would be most strengthened by the new information in the question Choose the answer choice which has the most direct relevance to that new information A: The new information tells us about Hemingways own reaction, not the reactions of critics (The assertion is made in lines 54-55 in the passage.) B: Yes This would act as a specific example in support of the more general assertion made in the passage that the authors own feelings tell us nothing about the value of his or her work (lines 52-54) C: The new information in the question makes no reference to Hemingways readers D: The new information in the question has no direct relevance to the authors discussion of readers varied reactions in the passage (in lines 35-36 and 44-47) 27 132 D A: This is stated by the author in lines 17-19 Given that formalist criticism assumes a standardized, abstracted ideal reader (lines 34-41) and so is not concerned with the fact that actual readers interpretations will vary, this statement if true would have no impact on the validity of formalist principles B: The author makes this assertion in the passage (lines 63-65) There is no inconsistency between this claim and the authors defense of the formalist focus on the structure of the work (lines 19-24) C: The only aspect of the authors intent with which formalist critics concern themselves is the authors intention as realized in the work (lines 31-34) Therefore, the inability to discern what the author intended to put into the work would pose no problems for formalist criticism D: Yes The author explains that formalist criticism looks primarily at the work itself (lines 19-20), and indicates throughout the passage that knowledge of the life and mind of the author is not important to an understanding of the authors work (lines 20-24, 31-34, and 61-63) If it were shown to be true that the social and historical context of a work cannot be ignored by critics, it would undermine the formalist claim that the author, and the authors own experiences, need not be considered Passage IX 133 A A: Yes If debris from a third ice sheet were found to predate that from the Laurentide and Icelandic sheets, it would support the claim that it was the collapse of that third sheet that caused the changes in the other two, and in the climate as well (see lines 44-47 and 65-68) B: This could still be explained by changes in the Laurentide sheet The author argues that the collapse of the Icelandic sheet could not be caused by changes in the Laurentide sheet, because the two were not connected (lines 16-22) However, according to the author, a glacier behind the Laurentide could move in synchronicity with it only if it were not a separate sheet (lines 20-23) C: Rafted debris deposited after debris from the Icelandic and Laurentide sheets could not be explained by a third sheets icebergs triggering changes that then caused the collapse of the other two It is much more likely that icebergs from one or both of the other two caused climatic changes which contributed to the collapse of other sheets, which then deposited their debris on top D: The existence of these currents would indicate that the Laurentide sheet was not the cause of the Heinrich events, but it would also weaken, not support the third sheet hypothesis (lines 57-65) 134 A A: Yes The author states in lines 38-41 that icebergs produced by a surging ice sheet could cause climatic changes by laying down a layer of cold water on top of warm ocean currents The author indicates that the theory described in this paragraph (based on changes in the Laurentide ice sheet) has been called into question, but not because of doubts about whether or not icebergs from ice sheets can lead to climatic changes (lines 42-47) Later in the passage (lines 57-61), the author also states that icebergs from a third ice sheet could have triggered temperature changes which then caused the collapse, and thus discharge of icebergs, from the Iceland and Laurentide sheets Therefore, the author would agree that icebergs can both cause and be caused by changes in the climate B: The author suggests that once Icelandic debris (deposited before or at the same time as debris from the Laurentide sheet) was discovered, it cast doubt on the claim that thickening of the Laurentide sheet caused surging which then created icebergs Because two separate sheets could not surge on the same cycle (lines 16-22), the Laurentide explanation is called into question, and it was that (now) debunked explanation which gave support to the hypothesis about surging Therefore, there is no evidence in the passage to suggest that the author would agree with this assertion C: Volcanoes are mentioned in line 44, but only as a source of debris, not as a cause of surging D: The studies described by the author use core samples to locate and trace to its origin debris deposited by icebergs, not as direct evidence of climatic change Furthermore, the author appears to accept the findings of those studies, indicating that he or she would, if anything, disagree with a claim that core samples could not be used as indirect evidence 28 135 B A: The time frame posited by the passage is 14,000 to 70,000 years ago (lines 25-27) Thus evidence from a million years ago would not be relevant B: Yes Bonds original explanation was called into question by evidence that icebergs from Iceland deposited volcanic debris at the same time or before the Laurentide icebergs (lines 42-55) If that debris were shown to be from Canada, it could have come from the Laurentide sheet [which at times covered North America (lines 6-7)] Thus Bonds original explanation (lines 4-11 and 23-41) could still be valid C: The fact that Earths core is cooling would have no effect on Bonds original hypothesis, which was not based on any particular core temperature or cooling rate (lines 34-36) D: Bonds original explanation was undermined by evidence of debris from a separate Icelandic ice sheet (lines 42-55) The fact that ocean currents have remained stable over a large part of the 56,000-year period in question would cast doubt on one particular alternative hypothesisthat temperature changes in ocean currents were the real cause of the Heinrich events (lines 62-65) However, it would have no effect on the evidence, or the interpretation of the evidence that cast doubt on the Laurentide explanation in the first place 136 D A: By providing some additional evidence that icebergs from the Iceland sheet deposited debris at the same time or before the Laurentide icebergs, this finding would decrease, not increase the probability that changes in the Laurentide caused surges (see lines 14-22) B: Evidence of additional debris from the Iceland sheet would have no direct relevance to the possibility that ocean currents were the real cause of collapse C: Evidence supporting the claim that another ice sheet was collapsing at the same time as the Laurentide would support, not undermine, the probability of an external trigger (lines 14-22 and 50-56) If the Laurentide could not have been the cause, it must have been some other factor D: Yes While this evidence supports the claim that there was a trigger external to both the Iceland and Laurentide ice sheets (see the explanation for choice C), it gives no reason to believe that this trigger was a third ice sheet (lines 57-61) rather than ocean currents (lines 62-65), or some other factor not mentioned in the passage 137 B A: While the author indicates that researchers believe that Heinrich events occur about every 7000 years (lines 2-5), none of their findings or interpretations of evidence are based on this time frame B: Yes If the debris layer came from asteroids rather than from ice sheets, it would seriously call into question both the Laurentide explanation and the criticism of that explanation All of the research described in the passage is predicated on the assumption that the debris was left behind by icebergs discharged from ice sheets If that assumption is false, the conclusions drawn at first about the action and effects of the Laurentide sheet, and later about the synchronized behavior of the Icelandic sheet, would be without foundation C: Evidence about how tightly glaciers adhere, and presumably then about how fast they might move, has no direct relevance to any of the research reported in the passage Glacial movement and friction were factors in Bonds original explanation (lines 31-38), but as far as we know, he did not claim any particular rate of speed that would be contradicted by this evidence D: The research in the passage, as described, is not based on the assumption that all cores must show debris This does not call into question the relevance of samples with debris that have been found, or the conclusions based on those findings 29 BIOLOGICAL SCIENCES Passage I 138 C Difficulty in exhaling would lead to an accumulation of CO2, since that is the gas that is exhaled CO2 is converted by carbonic anhydrase to carbonic acid, which dissociates into a hydrogen ion and a bicarbonate ion; the resulting accumulation of H+ would lead to acidosis (specifically, respiratory acidosis, since it is due to a failure in the respiratory system) O2 would not accumulate, and even if it did, this would not be converted to an acid and would have no effect on pH (choice B is false) The text of the question states that inhalation is not a problem, so there would not be a decrease in O2 intake (choice D is false) Note that choice A, while true, is irrelevant since it does not answer the question 139 C Neutrophils are phagocytic white blood cells that typically move to sites of inflammation via chemotaxis Erythrocytes are red blood cells and not participate in mediating inflammation (choice A is false), thrombocytes are platelets and play a role in blood clotting, not inflammation (choice B is false), and myocytes are not even a white blood cellthey are muscle cells (choice D is false) 140 B This sequence is described in the first paragraph of the passage Choice C also describes events in the proper sequence but lists events that occur several steps after T-lymphocyte activation, making B a better choice Choices A and D are false; histamine release leads to vasodilation, not vasoconstriction or bronchodilation 141 A The second paragraph states, One therapeutic strategy would be to target a particular subset of T lymphocytes known as T-helper (TH) cells, and goes on to describe how TH1 cells can inactivate the TH2 cells that are correlated with asthma Administering IgE may sensitize mast cells, leading to an asthma attack (choice B is false), and neither Zileuton nor colchicine is mentioned in the passage (so choices C and D are false) Passage II 142 D Figure shows that Drug C inhibits the binding of cells to both Fg and FN Choice D is the only choice that shows this 143 A Referring again to Figure 2, Drug A inhibits the binding of cells to Fg, but does not affect the binding of cells to FN This is the same effect as Drug D, described in the question text 144 C Figure shows that A5 cells can bind to both Fg and FN (statements I and II are true), but Drug C inhibits binding of A5 cells to FN (statement III is false) 145 B Since one would not expect water to affect the binding of cells to Fg or FN, and since Drug B does not affect the binding of cells to Fg or FN (choices A and C are false), it seems logical to assume that Drug B might have been water (choice B is true, and D is false) 146 C Since Drug C affects the binding of cells to both Fg and FN, it seems that this drug would be the one most likely to cause problems Drug A only affects the binding of cells to Fg (choice A is false), and Drug B has no effect whatsoever (choices B and D are false) 147 D Based on Figure 2, neither Drug A nor Drug B has an effect on the binding of cells to FN (choices A and B are false), and Drug C decreases the percentage of bound cells (choice D is true, and C is false) 30 Passage III 148 A From Table 1, we note that the reaction rate is dependent on both the concentration of Compound (Student group vs 3) and the concentration of sodium ethoxide (Student group vs 2) The rate-determining step is therefore bimolecular (E2, since this is an elimination reaction) Because E2 reactions involve a transition state in which two s bonds break to form one p bond in a concerted fashion, the students came to the correct conclusion Br Br CH3 H CH3 H H OCH2CH3 OCH2CH3 149 D The students described the cleavage of two s bonds in a concerted, one-step transition state to form a p bond This is characteristic of an E2 reaction 150 C Compound produces two unique alkenes due to the removal of a b-proton from the methyl group (to produce Compound 3) or from the ring (to produce Compound 2) The only alkyl halide that has two unique b-hydrogen atoms and can therefore produce two alkenes is choice C Note that choice A would yield a single terminal alkene, while choices B and D not generate alkenes under these conditions since either the bromine (choice B) or b-hydrogen (choice D) is bonded to an sp2-hybridized carbon 151 B Since this is an elimination reaction, the carbon atom bearing the leaving group (bromine) rehybridizes from sp3 to sp2 152 B Without a base (NaOCH2CH3) to promote an elimination reaction, Compound will undergo a substitution reaction with ethanol (a nucleophile) to produce choice B Since the alkyl halide is tertiary, it can ionize to form a relatively stable carbocation, making this substitution reaction unimolecular (SN1) Passage IV 153 B These bacteria are described in the passage as producers of toxins that are superantigens; i.e., antigens that produce an exaggerated immune response The passage does not discuss their reproduction (choice A is false) or the inhibition of metabolic enzymes (choice D is false) Autoimmune reactions, by definition, are abnormal immune reactions to normal cellular antigens, not to bacterial antigens (choice C is false) 154 B The primary structure of proteins is their amino acid sequence The secondary structure of proteins involves interactions between the backbone of the peptide chain to form structures such as a-helices and b-sheets (choice C is false), and the tertiary structure of proteins involves interactions between amino acid side chains to form the overall three dimensional structure of the protein (choice D is false) The isoelectric point of amino acids has nothing to with their sequence in a particular protein (choice A is false) 155 C The passage states that TSS is characterized by a high fever, hypotension (circulatory system), and a rash (skin) Fever is a non-specific disease defense mechanism, and of the four systems listed as answer choices, the lymphatic system is most directly involved with disease defense 156 C The passage states the conventional antigenic stimulation activates in 100,000 T lymphocytes, or 0.001% Superantigens activate 20% of T lymphocytes, or 20,000 of 100,000 cells 157 D If the dose of Strain A required for infection is greater than the dose of Strain B required for infection, then Strain A must be less potent than Strain B (choices A and C are false) More specifically, since the dose of Strain A required for infection is twice the dose of Strain B required for infection, Strain A must be half as potent as Strain B (choice D is true, and B is false) 31 Independent Questions 158 A Adding a repressor protein that binds to the superantigen gene would prevent its transcription (and its subsequent translation; choice B could prevent synthesis and can be eliminated) Adding a complementary nucleic acid sequence that can bind to superantigen mRNA would prevent its translation (choice C could prevent synthesis and can be eliminated) Adding a stop codon within the superantigen gene would result in a stop codon in the superantigen mRNA upon transcription This would terminate protein synthesis prematurely when the mRNA was translated (choice D could prevent synthesis of the complete protein and can be eliminated) However, tRNA nucleotides that bind to both mRNA and ribosomes are normalthis is how mRNA is translated Adding more of these nucleotides would not prevent (and may enhance!) translation of the superantigen protein (choice A would not prevent synthesis and is the correct answer choice) 159 B The O at position a is the same as the corresponding O in the hemiacetal, so choice A is eliminated The hydroxyl group in the hemiacetal is released and replaced by the OCH3 (methoxy) group of methanol So, the oxygen at position b comes from the 18O labeled methanol, while the oxygen at position c comes from the released hydroxyl group 160 D The terminal amine of phenylhydrazine (recall that hydrazine is H2NNH2) will react with the carbonyl shown in the question (similar to imine formation) The first step of this additionelimination reaction is addition H+ O CH3 HO CH3 OH CH3 addition HN elimination N NHPh NHPh H2N NHPh phenylhydrazine 161 D Parthenogenesis (choice D) is the activation and subsequent development of an egg without the use of a sperm, for example by pricking it with a fine needle Isogamy (choice A) is a condition in which male and female gametes are visibly indistinguishable, but this does not preclude their ability to join in sexual reproduction Hermaphroditism (choice B) and pseudohermaphroditism (choice C) are states in which a single animal produces both sperm and eggs and is able to selffertilize; although unusual, they are examples of sexual reproduction 162 C If there are 12 nucleotide base pairs for every complete 360 turn of the helix, there must be one base pair for every 30 of the turn This most closely corresponds with the data for the Z conformation of DNA given in the question text Passage V 163 C As stated in the passage, isoprene is a 5-carbon unit; two isoprene groups form a terpene Cembrene (Compound 7) has 20 carbon atoms, making it a diterpene (20 carbon atoms = isoprene units = terpene units) b-Elemene (Compound 9) has 15 carbon atoms (3 isoprene units = 1.5 terpene units), making it a sesquiterpene 164 C Conjugated p bonds produce strong UV absorptions While Compound has three double bonds, they are not conjugated, and will therefore not produce a strong UV absorption (eliminating choice A) While hydroxyl groups (choice B) and carbonyl groups (choice D) are prominent in IR spectroscopy, they not produce strong UV absorptions 165 A ()-b-Elemene (Compound 9) is shown in Figure in the passage Its enantiomer, (+)-b-elemene, will have the opposite stereochemistry at all three stereocenters Note that choices B and D have only two of the three stereocenters inverted, and choice C has only one 32 166 D Since the procedure must convert an ester functional group (OAc) into an alcohol functional group (OH), choices A and C are eliminated, and condensation (choice B) does not apply here The answer is D: Saponification is the hydrolysis of an ester using a base 167 A In thin-layer chromatography (TLC), the stationary phase is highly polar, while the mobile phase is less polar Compounds that are more polar therefore have greater affinity for the stationary phase and a slower migration Compound 5, with its two hydroxyl groups, is the most polar of the four compounds listed in the answer choices and will therefore migrate the slowest Passage VI 168 A Referring to Figure 2, it is clear that since the gene is being expressed in some tissues and not in others, it is not spreading widely throughout the fetus (choices C and D are false) Furthermore, since some of the organs in which the gene is expressed are large (such as the liver) and some are smaller (such as the pancreas), it is not only expressed in the largest organs (choice B is false) However, all of the organs in which the gene is expressed are abdominal organs, making choice A the best choice 169 D The passage describes the cationic lipids as being positively charged, so DNA must be negatively charged (choices A and B are false) Furthermore, the whole reason the DNA must be coated with lipids in the first place is because it is too hydrophilic to easily cross the cell membrane on its own (choice D is true, and C is false) 170 B The cell membrane does not contain DNA In eukaryotes, DNA is found in the nucleus, and in prokaryotes it is found in the cytoplasm (choices C and D are false) Furthermore, the cell membrane is not a pure lipid bilayer; it contains proteins in addition to phospholipids, cholesterol, and carbohydrates (choice B is correct, and A is false) 171 C The only cells that are passed from parent to offspring are the germ line cells (eggs and sperm) All other cells are somatic cells and are not passed on to the next generation; thus, a gene introduced to a somatic cell could not be passed on to offspring (choice C is true, and choices A and B are false) Furthermore, any DNA contained within a germ line cell, be it original cellular DNA or introduced DNA, will be passed on (choice D is false) 172 A All cells in a multicellular organism contain the same genome, inherited from the original egg and sperm that fused during fertilization (choices C and D are false) What makes one type of cell different from another type of cell is not the DNA it contains, but the specific genes within that DNA that are or are not expressed Since all cells not express the same genes, cells can vary widely in their appearance and function (choice A is true, and B is false) Passage VII 173 A The passage states that fighting big fires is a frightening experience Frightening and/or stressful experiences activate the sympathetic division of the autonomic nervous system, which, among other effects, acts to increase the heart rate (choices C and D are false) Since the passage goes on to state that Steves experience was especially frightening, one can assume that his heart rate would be more affected than Joes (choice A is true, and B is false) 174 C Since Joe has suffered extreme skin scarring (as described in the passage), he would have more difficulty cooling by sweating than Steve Older males have lower metabolic rates than younger males and would therefore tend to have lower body temperatures (choice A is false), and if Steve has a greater percentage of body fat than Joe, Steve would tend to overheat more easily than Joe (choice B is false) Furthermore, if Steve weighs half as much as Joe (as stated in the passage), then he has a greater surface-to-volume ratio than Joe (choice D is false) 175 C The oxygenation of blood can be affected by many things, including the rate and depth of breathing (increases in these values can lead to greater oxygenation, choice A is false), hemoglobin concentration (increases in [Hb] can increase oxygenation, choice B is false), and alveolar surface area (decreases in surface area, such as in emphysema, can decrease oxygenation, choice D is false) However, blood pressure in the pulmonary artery is unlikely to affect oxygenation, making C the best answer choice (Note, however, that if blood pressure dropped dramatically, oxygenation would be affected, but of the four choices given, this is the least likely to have an effect.) 33 176 D Since glomerular filtration rate (GFR) is directly proportional to blood pressure, increases in blood pressure would lead to increases in GFR Therefore, if Steves blood pressure increased more than Joes, one would expect Steves GFR to increase more than Joes (choice D is true, and A is false) Reabsorption rate is not affected by blood pressure (choices B and C are false) 177 C Since Joe weighs twice as much as Steve, he would require more energy to perform the same work tasks (choice C is true and A is false) Choice B is contradictory; an individual with a greater basal metabolic rate would not consume less energy Choice D is irrelevant, since the question asks about the energy involved in performing work, not the energy involved in maintaining the body at rest (basal metabolic rate) 178 D Since the liver is not involved in the production of digestive enzymes (choice A, the job of the pancreas), antidiuretic hormone (choice B, the job of the hypothalamus), or new blood cells (choice C, the job of the bone marrow), damage to the liver should not affect their production However, since the liver is directly involved in the production of bile salts, liver damage should reduce their production 179 B The blood pressure of the firefighters is given in the passage as 125/70 mm Hg; this represents the systolic blood pressure over the diastolic blood pressure The systolic blood pressure (125 mm Hg) is the pressure measured when the heart is contracted, and the diastolic blood pressure (70 mm Hg) is the pressure measured when the heart is relaxed (choice A is false, and B is true) Note that both choices C and D refer to the pressure when the blood is entering an artery (in other words, when the heart is contracting), thus these measurements must be systolic measurements (choices C and D are false) Passage VIII 180 A The aldol/decarboxylation reaction will begin (in the presence of a base) with the deprotonation of the diacid to produce a nucleophilic enolate The primary function of pyridine is to facilitate this deprotonation (choice A) [Note that pyridine will also deprotonate the carboxylic acid functional groups of the diacid (choice B), but this does not result in their neutralization, as the answer choice says.] 181 B SOCl2 converts carboxylic acids into acid chlorides (and alcohols into alkyl chlorides) 182 C Since the methyl groups replace all four carbonyl a-protons, enolization is not possible (choice C) 183 D By analogy to the passage, methyl propenoate would be converted to 1-propanol: OCH3 OCH3 H2/Pd/C condition d LiAlH4 OH condition e O O methyl propenoate methyl propanoate 1-propanol Condition d results in the reduction of the double bond, while condition e (followed by an acidic workup) reduces the ester to an alcohol 34 184 B The passage states that Compound was reacted with 2-methylpropanoic acid in the presence of the strong base lithium diisopropylamide (LDA) LDA deprotonates 2-methylpropanoic acid (first at the carboxylic acid, then at the aproton) to generate an enolate This enolate then reacts with Compound to give choice B: CO2Li+ OH LDA O 2-methylpropanoic acid OLi+ equivalent Compound H+ choice B OLi+ equivalents CO2Li+ Independent Questions 185 D The function of antidiuretic hormone (ADH) is to allow the kidney tubules to reabsorb more water, thus retaining water in the body After being dehydrated for two days, the hikers ADH levels would be expected to be high Glucocorticoids (choice A) have various jobs, including reducing inflammation and raising blood glucose during stress, aldosterone (choice B) increases Na+ retention, and insulin (choice C) lowers blood glucose 186 A Endocytosis is the uptake of extracellular material Phagocytic cells of the immune system, such as macrophages (choice A) and neutrophils, would be expected to have the highest rates of endocytosis Erythrocytes (choice B) are red blood cells and function in oxygen transport, osteoblasts (choice C) are bone-building cells, and neurons (choice D) send nerve impulses between the brain, spinal cord, and body organs 187 C Antibody proteins are synthesized by B-cells and secreted into the blood Secreted proteins are translated by ribosomes attached to the endoplasmic reticulum (specifically, the rough ER) The nucleus and mitochondria are not associated with protein translation (choices A and B are wrong), and while the Golgi apparatus is involved in the secretory pathway (the proteins would interact with the Golgi), it is not specifically involved in the translation (C is a better answer choice than D) 188 C Transmission at the neuromuscular junction (NMJ) is chemical in nature Neurons release ACh onto muscle cells; the ACh binds to receptors on the muscle cells and triggers their depolarization (and thus their contraction) The ACh is then degraded by a cholinesterase found at the NMJ Addition of a cholinesterase blocker would prevent the degradation of ACh, thereby prolonging the stimulation of the muscle and preventing it from repolarizing in order to receive another impulse (choice A is true and eliminated) Addition of a toxin that prevents the release of ACh would certainly interfere with impulse transmission; if the neurotransmitter cant be released, the muscle cells cannot be stimulated (choice B is true and eliminated) Addition of a substance that binds to ACh receptors would prevent ACh from binding and prevent impulse transmission to the muscle cell (choice D is true and eliminated) The only choice that would not interfere with transmission is choice C; an increase in ACh receptor sites would enhance impulse transmission 189 C The fact that the lens fails to form in the absence of the optic cup indicates that the optic cup is necessary for lens development, and may in fact induce it This says nothing about the timing of neurulation relative to gastrulation (choice A is false), or about the specific timing of eye development (choice B is false) Choice D is a false statement in addition to being irrelevant; cell differentiation is a gradual process, not an all-or-none event, and in any case, this says nothing about the relationship between optic cup development and lens development 35 Passage IX 190 A The passage states that if the Xi genotypes are not selected against, the frequency of Xi should increase to 100% Thus all males would have the XiY genotype and sire only daughters, and the population would become increasingly female (in other words, not stable, choices B, C, and D are false) Ultimately, the entire population would be female and would become extinct 191 A The last paragraph of the passage gives a clue that the affected process might be meiosis, since the XiY males are apparently defective in properly segregating their sex chromosomes Further, in the second paragraph the passage states that the total reproductive output of the XiY males is not affected If mate recognition (choice B), courtship behavior (choice C), or genital development (choice D) were disrupted, total reproductive output would be reduced (choices B, C, and D are false, and choice A is true) 192 C The words random mating are a tip-off for HardyWeinberg genetics Since all males receive a Y chromosome from their fathers, the male contribution can be ignored; we are only interested in the type of chromosome the females will donate Let us arbitrarily assign Xi as p in the HW equations, and Xs as q 15% of the females are XiXi (15% pp), 50% are XiXs (50% pq), and 35% are XsXs (35% qq) Plugging these values into the HW equation for genotype frequency (pp + 2pq + qq = 1) gives us 0.15 + 0.50 + 0.35 = 1; solving for p and q gives us approximate values of p = 0.4 and q = 0.6 Since HW equilibrium requires that allele frequency remain the same from generation to generation, and since males can only inherit either Xi (p) or Xs (q), the proportion of XiY males is simply the frequency of the Xi allele: p = 0.4 = 40% 193 D The passage states that none of the Xi genotypes are selected against; therefore, no Xi genotype can have greater fitness than another (choice A is false) There is nothing in the passage to suggest that XiXi flies are more likely to migrate than any other genotype (choice B is false) Since females have only X chromosomes to donate, they have no choice but to pass their X to all their offspring, and there is nothing in the passage to suggest otherwise (choice C is false) Choice D is true; since XiY males sire only daughters, all their offspring receive their X However since XsY males sire equal numbers of daughters and sons, approximately half their offspring receive an X and half receive a Y 194 A Since the original female produced both sons and daughters, the male she mated with must not have been XiY (choices B and D are false) Furthermore, since some of her sons sire only females, and some of her sons sire both males and females, she must be XiXs; sometimes she passes on Xi to her sons, and sometimes she passes on Xs (choice C is false) 195 C The characteristics of the occasional sons of XiY males are that they are viable (choices A and B are false), sterile (choice C is true), and of normal appearance (choice D is false) 196 B The passage states that the Xi frequency will reach 100% if all genotypes have equal fitness (are not selected against) If we want to prevent Xi frequency from reaching 100%, then all genotypes must not have equal fitness (choices C and D are false) In other words, some genotypes must have greater fitness than others; if the balance is to be swayed toward Xs, then these genotypes must have the greatest fitness (choice B is true, and A is false) Passage X 197 A This question is difficult because it is hard to decipher precisely what the question is asking The best bet is to eliminate incorrect or irrelevant choices, based on the theme of the passage The main theme here is that altered expression of particular genes during development, or possibly mistakes in transcript processing, could lead to disease There is no reason to assume that certain genes are better targets for mutation than other genes, so choice C is false Choice D may be true, but does not fit the theme of the passage, so choice D is eliminated Both choices A and B are reasonable answers, but since the passage specifically discusses how gene expression is altered in this particular disease (NF1), choice A is a better response than choice B 36 198 D The passage describes this disease as having a wide variety of clinical features, including skeletal abnormalities, learning disabilities, and tumors Clearly these clinical manifestations not affect the same tissues (choice A is false), and they not arise from the same cell type (choice B is false) The passage says that the disease could arise from a single genetic defect, but that the wide variety of symptoms makes this unlikely Furthermore, the entire point of the passage is that altered expression of genes can lead to a variety of protein products from a single gene sequence, and that abnormal expression can lead to disease This makes choice D better than choice C 199 A Changes in a genes transcript (i.e., its mRNA) will result in changes in the protein product, not in the gene itself (choice D is false) or in its transmission (choice C is false) Protein is translated (synthesized) by ribosomes, not transcribed by ribosomes (choice A is true, and B is false) 200 B The mechanisms that regulate gene expression are not simple; in fact, this is stated in the passage in the last paragraph (choices A and D are false) Further, this passage describes differences in mRNA transcripts, so the mechanisms cannot affect only DNA (choice B is true, and C is false) 201 C One of the main reasons that differentiated cells are different from one another, in both structure and function, is that they produce different proteins Pancreatic cells, for example, produce insulin but not acetylcholine; neurons produce ACh but not insulin This can explain why different transcripts are needed as cells differentiate Note that although choices A, B, and D all represent true statements, they fail to answer the question; they not explain the need for different transcripts, making choice C the best option 202 A Epigenetic (developmental) modulation of gene expression is important in evolutionary terms, because it allows the expression of multiple types of protein from the same basic DNA sequence In other words, it allows greater variability within an organism (and thus possibly greater fitness within the population); choice A is true Choice B may be a true statement, but this is not epigenetic modulation as described in the passage (choice B is eliminated) Posttranslational modification of defective proteins will have a limited function in evolution at best, since proteins are not passed down from generation to generation It is much more likely that modification of functional genes (that can be passed down to the next generation) would play a greater role (choice C is false) Choice D is false because, again, epigenetic modulation of gene expression involves changes in RNA, not variability in DNA 203 D If NF1 is caused by a dominant allele, then individuals who are homozygous dominant (DD) or heterozygous (Dd) could display this disorder Choices A and C are characteristic of recessive disorders (in which the homozygous recessive genotype is necessary for the disease to be expressed), and choice B is not true of any disease-causing allele Passage XI 204 C Since the alkoxide used in Student 2s proposal is t-butoxide, t-butanol should be used as the solvent This will prevent the deprotonation of solvent by t-butoxide from forming any undesired products For example, if methanol were used as a solvent, dimethyl ester could be produced: (CH3)3COK+ CH3OH (CH3)3COH + CH3OK+ CH3X CH3OCH3 205 A There are groups of nonequivalent protons in the desired product, in a ratio of 3:9 (or 1:3) b CH3 a CH3O C b CH3 CH3 b Neither of these groups has any neighboring protons, so they will both appear as singlet peaks in the 1H NMR spectrum (eliminating choices C and D) Since (the protons in) Group a are closer to the electron-withdrawing oxygen atom, they will appear farther downfield, eliminating choice B 37 206 B The reaction shown in the second step of Student 2s scheme is a substitution reaction (eliminating choices C and D), since one s bond is broken and one is formed Since the electrophile is a primary alkyl halide, it will not form a carbocation, and the reaction must proceed by an SN2 mechanism 207 D The aromatic halide Ar3CX (Ar = aryl or aromatic; for example, Ph3CX) is not only a tertiary halide (favoring carbocation formation), but the resultant carbocation is stabilized by resonance with the three aromatic rings Therefore, Ar3CX readily forms a carbocation to undergo SN1 reactions with alcohols 208 A The reaction of a general dihalide, R2CX2, with two equivalents of alkoxide will produce an acetal, R2C(OR)2 Independent Questions 209 D The distal tubule and collecting duct have variable water permeability based on the presence of ADH; in its presence they are water-permeable (allowing increased water retention by the body), and in its absence they are waterimpermeable (allowing increased water elimination in the urine) The glomerulus (choice A) is the site of blood filtration, Bowmans capsule (choice B) is the tissue surrounding the glomerulus, and the loop of Henle (choice C) is a site of water reabsorption, but it is not affected by ADH 210 D Since the disease is more prevalent in males than in females, it must be sex-linked (choices A and B are false), and since it skips generations (in most cases), it is most likely a recessive disorder (choice C is false) 211 B It is clear from the question text that an attempt to run glycolysis is being made However, glycolysis requires an input of two ATP molecules before any ATP or lactic acid can be produced O2 (choice A) is not required; the text states that this is an anaerobic experiment NADH (choice C) is a product of glycolysis, not a substrate Acetyl-CoA (choice D) is produced from pyruvate under aerobic conditions, and again, is not a substrate in glycolysis 212 D Recall that bromine reacts with alkenes to produce dihalides, a reaction which decolorizes bromine Based on the table given, tung oil contains the most double bonds, since its hydrolysis results in primarily dienoic and trienoic acids Tung oil will therefore decolorize the largest volume of bromine 213 B Epinephrine is released from the adrenal medulla under sympathetic stimulation and is not regulated by the anterior pituitary at all The release of cortisone (choice A), progesterone (choice C), and thyroxin (choice D) are controlled by ACTH, LH, and TSH, respectively, released from the anterior pituitary 214 C Bone consists of calcium phosphate crystals deposited on a collagen matrix (choices A and B are false) Collagen has a unique triple-helix structure that depends on the presence of hydroxylysine and hydroxyproline residues for stability (choice D is false) The only substance listed here that is not required in bone is potassium (choice C) 38 ... faster, because it has a lower molar mass than Gas Y 53 B A catalyst has no effect on a reaction at equilibrium, so the amount of ammonia at equilibrium with a catalyst will be the same as the amount... that they did not already know This would weaken the author’s claim that audiences are already aware of what marketers are doing D: The passage deals with the appearance of products and brands... this range as well, and thus be much less than (Granted it’s small, so we could say that it’s “near zero,” but the fact that Ka values can actually be measured and used in calculations means that