MCAT TPR Exam 2

MCAT 101 EXAM 2 STUDY GUIDE 1. Explanation: This is an Analogy question. A: No. Since the example includes environmental factors, this answer choice is incomplete. B: No. The example emphasizes an interaction among factors; this answer choice refers only to the innate condition or internal makeup of the computer. C: Yes. The interaction between the innate condition of the airplane and the force of the air in its environment illustrates the same principle as the can and the weight of the car. D: No. Since the example includes environmental factors, this answer choice is incomplete. 2. Explanation: This is an Inference question. A: No. See paragraph 1. The author believes that some causes of schizophrenia are important. B: No. See paragraph 5. This shows the relationship between environment and individual constitution; the examples of patients that follow imply that the stronger the individual’s constitution, the less likely the patient is to succumb to environmental stress. This choice is too extreme. C: Yes. See paragraph 4. Including himself, the author states that practitioners should focus on environmental, or exogenous, factors. D: No. See the final paragraph. The author encourages researchers, not practitioners, to focus on causes within the individual. 3. Explanation: This is a Weaken question. A: No. The author argues that it is currently impossible to treat schizophrenia genetically. This choice, describing limitations on genetic engineering, is consistent with that position. B: Yes. If treatments are currently available which alter the “individual’s genetic design,” then this directly contradicts the author’s reason for focusing on environmental factors (genetic engineering is currently impossible). C: No. The author states that current knowledge allows us to work with the patient’s environment, not that every patient’s environment is or can be made to be ideal. This choice therefore does not weaken the author’s recommendation. D: No. The author does not claim that schizophrenia can be completely cured; this does not contradict his recommendation. 4. Explanation: This is a Structure question. A: No. The author does not indicate that the causes are simple, but rather that they are complex and interconnected. B: No. Psychological problems, according to the author, arise from the interaction between environmental and internal factors, not from one or the other alone. C: Yes. See paragraph 3. The examples used to illustrate the cause-and-effect relationships emphasize the importance of both exogenous (environmental) and innate factors. D: No. See paragraph 3. The author does not indicate that the causes are too complex, only that they are very complex and psychiatrists must take into account the relationships among factors. 5. Explanation: This is a Structure question. A: No. See paragraph 2. The author does not present causation as a philosophical concept. B: No. See paragraph 2. The author believes that perception depends upon perspective (from the perspective of either nature or environment); this answer choice is too narrow. C: No. This choice contradicts the passage. The author indicates that no environment (which in this case would include upbringing) is ideal. Psychological health is based on an interaction of environment and internal constitution such that there are enough positive factors in one or both to prevent significant dysfunction. D: Yes. See paragraph 2. This is the main argument in the passage; environmental and internal factors are the different perspectives mentioned in the claim. 6. Explanation: This is an Inference question. A: Yes. Psychiatric researchers should explore the causes of illness from the perspective of the individual. B: No. Psychiatric practitioners, not researchers, should focus on environmental causes. C: No. This is a trap based on the idea that internal and external factors “interact” to create illness; no “interaction-oriented cures” are outlined in the passage. D: No. See the last paragraph. Research may well involve some theorizing. However, the author argues that psychiatric researchers should focus primarily on the practical goal of learning more about the individual constitution in order to provide more effective treatment. Be careful to pay close attention to words like “primarily” or “chief” when they appear in the question stem. 7. Explanation: This is a New Information/Roman numeral question. I: False. The author does not argue that we are unable to understand or affect any sort of internal function, only that we cannot manipulate genetic design. The passage gives no evidence that we cannot improve immune system function in other, non-genetic ways. II: False. While the author would argue that environment plays a role, neither the passage nor the question stem indicates that upbringing, one specific aspect of environment, would be a factor in all (non-psychological) disease. III: True. This is the author’s main argument; reactions to the environment, such as infections, are produced by the interaction between environmental and innate factors. 8. Explanation: This is a Vocabulary-in-Context question. A: No. This word is too weak. Trees do still play a significant role, as sources of food, medicine, and other products. The author’s argument in the last paragraph is that trees no longer play a primary or central role. B: Yes. Principal is a synonym for paramount; both indicate that society in the past, unlike today, depended on trees. C: No. While trees may be less valued and important than they were in the past, the author indicates in paragraph 2 that they continue to be valued to some extent today. D: No. "Important" is a synonym for "significant", and so has the same problems as choice A. Note that if two choices are equivalent, neither can be the credited response. 9. Explanation: This is a New Information/Roman numeral question. I: Yes. Although it may sound unlikely, the use of trees in producing plastic is mentioned in paragraph 2. II: True. The passage states that trees are used to make paper, by which we could infer the significant role of trees in manufacturing books. III: False. The author states that trees “at one time” were our only fuel source, and argues in the last paragraph that trees no longer play a primary role in our lives. Thus, there is no support in the passage for the conclusion that trees still play a significant role in the production of energy. 10. Explanation: This is a New Information/Roman numeral question. I: False. Although this assertion is made in the passage, it is not directly relevant to constructing bows. II: False. This assertion is not made in the passage. III: True. This assertion is made in the passage and, if true, would be directly contradicted by the anthropologist’s discovery. 11. Explanation: This is an Inference question. A: No. Measured planks do not provide data regarding total tree height. B: No. This answer choice lacks specific information concerning the height of trees; in addition, virgin white pines are not specified. C: No. This answer choice directly contradicts the passage. D: Yes. If they “typically” did not record the sizes of the trees, then they may have left written records of the sizes of a few specimens. 12. Explanation: This is a New Information question. A: No. The question asks about modern Americans, not about the beliefs of our forebears; the author does not draw a connection between the two. B: No. The question asks why we might know little about the history of the horse. This choice does not explain the reason for the historians’ lack of interest, based on information provided in the passage. C: No. As in choice B, this answer does not explain our lack of information, it just describes it. D: Yes. The author states that the reason historical facts are forgotten is the lack of a relevant connection to modern life. 13. Explanation: This is a Strengthen question. A: No. None of these enterprises has a clear connection to past beliefs or to the healing properties of sassafras. B: No. There is no connection between “doctors today” and past Native American beliefs. C: No. The medicinal taste provides no evidence for past beliefs or for healing properties. D: Yes. Native Americans’ drawings act as evidence for their beliefs that sassafras oil had healing properties. 14. Explanation: This is a Retrieval question. A: No. While commercial sandpaintings may be sold as souvenirs, the author does not indicate that they are inexpensive. In fact, the passage indicates just the opposite by including souvenirs under the heading of “luxury items.” B: No. See paragraph 2. Commercial, not traditional, sandpaintings are sold in an international market. C: Yes. See paragraph 3. Commercial sandpaintings are in demand by the American public. D: No. See paragraph 2. Commercial sandpaintings are not valued by the Navajo. 15. Explanation: This is an Inference/Roman numeral question. I: True. See the final paragraph. The passage suggests that the (false) idea that Navajo religion was dying out helped convince singers to create commercial sandpaintings as well as ritual ones. II: True. See the final paragraph. The coexistence of both commercial and religious “art” is more likely to occur in pragmatic cultures. III: True. See the final paragraph. The coexistence is more likely to occur in cultures receptive and willing to adapt to change. 16. Explanation: This is a Retrieval/EXCEPT question. A: Yes. See paragraph 1. Religious sandpaintings served as impermanent altars. Because this is an EXCEPT question, the correct answer will not be found in, or will contradict, the passage. B: No. They serve as a temporary resting place of holiness. C: No. They were filled with supernatural power. D: No. They were used in curing ceremonies to help cure illness. 17. Explanation: This is a Structure question. A: No. This quote is not directly relevant to the contrast drawn by the author between the controversial commercialization and secularization of sandpaintings and the sale of inherently secular crafts. B: Yes. The author’s purpose in referring to other, secular Navajo crafts is to show through contrast why “the development of permanent sandpaintings posed problems” or incurred sanctions. Therefore the quote in this choice, which illustrates the other side of the contrast, is most relevant to the quote given in the question stem. C: No. This answer choice is not relevant to supernatural sanctions placed on those who create or sell secular art. D: No. This answer choice is not relevant to supernatural sanctions. 18. Explanation: This is a New Information question. A: No. This answer choice emphasizes the actual punishment of a crime, not the mystery story that is the focus of the question. B: No. This answer choice does not address mystery stories in particular. C: No. The passage refers to our comfort with the legal system in a democracy, not to comparative level or number of comforts attached to life in a democratic system. D: Yes. See paragraph 3. The author asserts that citizens of democracies enjoy the mystery story because through it, collectively agreed upon morality is upheld; we can infer that citizens of dictatorships do not derive the same type of satisfaction due to their lack of political participation. 19. Explanation: This is a Weaken question. A: No. This claim is made by the author himself in the passage (paragraph 3). The author never claims that the two are identical, only that they serve almost the same purpose. B: No. See paragraph 2. The author indicates that the audience found pleasure in the wrongdoer’s punishment. C: No. See paragraphs 2 and 3. “Apt punishments” were given to wrongdoers of “antisocial acts.” D: Yes. If modern mysteries portrayed criminal behavior not as the sole responsibility of the criminal, but as caused by external factors, this would be inconsistent with the morality play’s focus on locating evil within the individual wrongdoer and imposing a just punishment (paragraph 2). 20. Explanation: This is a Weaken question. A: No. The passage does not claim that colleges and universities only teach "true literature"; therefore, mystery stories could be taught and not be considered "true literature." B: No. The passage does not claim that literary critics only give favorable reviews to "true literature." C: No. Popular and lucrative works of fiction may not have the qualities of "true literature." D: Yes. See paragraph 1. Since this is the only paragraph in the passage that discusses "true literature," the correct answer must be found in statements made in the first few lines; if all "true literature addresses fundamental issues of human existence," and mystery stories do address these issues, then mysteries must have at least one essential quality of true literature. 21. Explanation: This is an Inference/LEAST question. A: Yes. See paragraph 3. The power or “propulsive force” of a mystery is our “instinct for justice.” Secondarily, mysteries keep the readers’ interest by making the story entertaining (lines 41-49). Similarity to the readers’ lives is never mentioned or suggested as a factor. B: No. According to the passage, mystery stories reflect the criminal “transgressions” of the twentieth century. C: No. See paragraph 1. Since the author indicates that mystery stories have the same fundamental conflicts as morality plays, we can infer that the author believes mystery stories are literature. D: No. See paragraph 2. The passage states that the stakes are higher in modern mysteries. 22. Explanation: This is a Retrieval question. A: No. See the explanation for D below. B: No. See the explanation for D below. C: No. See the explanation for D below. D: Yes. See paragraph 3. The “instinct for justice” propels the mystery story. 23. Explanation: This is an Inference/Roman numeral question. I: True. The analogy implies that we celebrate a common set of beliefs through the mystery story that are similar to those beliefs celebrated through the arts (“song and verse”). II: False. Expressing common beliefs through music and poetry is equated to expressing beliefs through the mystery story; one is not said to be “better” than the other. III: False. This implies a contrast between the arts and the mystery story; the passage shows that they both celebrate the nation. 24. Explanation: This is an Inference/EXCEPT question. A: Yes. The problem lies in the lack of full economic, not political independence (paragraph 2). B: No. See paragraph 5. Inadequate agricultural policies have led to food shortages in Africa. C: No. See paragraph 6. Corrupt politicians created self- serving policies leading to food shortages. D: No. See paragraph 5. Many people migrated to urban areas, leaving less labor force for agriculture. 25. Explanation: This is a Weaken question. A: No. This answer choice is unrelated to the transfer of power in Africa. B: No. This answer choice is unrelated to British rule. C: No. This answer choice is unrelated to the transfer of power. D: Yes. If Great Britain continues to provide support, then this would directly contradict the author’s contention that economic cooperation collapsed. 26. Explanation: This is a New Information question. A: Yes. The passage identifies decline in food production for local consumption as a fundamental problem (paragraphs 3 and 4). B: No. The passage identifies current dependence on foreign food, not on foreign experts as the problem. Nothing in the passage or the question stem indicates that foreign technical aid or advice would recreate the dependency created by British colonialism. C: No. The author argues that dependency on Western food aid is part of the ongoing problem, and that longterm, not shortsighted solutions are needed. D: No. Lack of economic productivity is in fact an issue, but emphasis on exports over local consumption is part of the problem, not a likely aspect of a solution, based on the passage. 27. Explanation: This is a Main Idea question. A: No. This choice is too broad. The author only discusses how this was true in post-colonial Africa. B: No. This choice is too narrow. It covers only the last paragraph, leaving out the author’s discussion of the shortage of food production for local consumption in paragraphs 3-5. C: No. This choice is too extreme. While the author clearly believes that the problem is serious, the passage offers no call to action, nor any specific solution. D: Yes. This choice covers all of the major themes in the passage, including both the causes and the specific nature of the problem. 28. Explanation: This is an Inference question. A: No. See paragraph 5. Reducing the power of the urban elite would not have given financial incentives to farmers, and thus would not have had the greatest impact. B: No. See paragraph 5. If incentives did not exist for farmers to produce food, then aid would not have had the greatest impact. C: No. See paragraph 5. Population growth was not believed to be the main cause of the food crisis in Ghana in the 1970s. D: Yes. See paragraph 5. The “low price incentives” to Ghanaian farmers was the key restraint on productivity suggested by the passage. 29. Explanation: This is an Inference question. A: No. Caution in exploitation of natural resources was not the main obstacle; Africa is “fabulously wealthy” in terms of natural resources (paragraph 2). B: No. See paragraph 2. According to the author, Africa is not really “free” due to slow economic development; while political freedom was occurring, more attention needed to be paid to economic independence. C: No. The passage does not indicate that the author believes that knowing the history of agriculture would have helped African nations achieve better progress. D: Yes. See paragraph 2. Slow economic development and insufficiently productive economies held African nations back from achieving better progress. 30. Explanation: This is an Inference/EXCEPT question. A: No. See the last two paragraphs. Both climate and hunting by Paleo-Indians are given as likely causes of massive extinctions. Therefore, this choice is supported by the passage. B: Yes. See the last two paragraphs. Condors, teratorns, and vultures suffered because of the devastation of large mammals on which they depended. The passage indicates that these mammals may have died due to climatic change as well as hunting, but destruction of the habitat of condors and other birds is never mentioned. The trap lies in the discussion of destruction of habitats of other types of birds. C: No. See the final paragraph. Climatic warming occurred during the same period as the arrival of humans to the New World across the Bering Strait. D: No. See the final paragraph. Coniferous forests began to migrate northward as the climate changed. 31. Explanation: This is a New Information question. A: No. See paragraph 4. Because of different contexts, we cannot assume that the Inuits would act as the Paleo-Indians did. B: Yes. If Denali Park includes “ecological islands” similar to Centinela, with human settlement and development, then the process of deforestation and a resulting decrease of diversity would most likely result. C: No. See the final paragraph. Because of different contexts, we cannot assume the same chain of events would occur in Denali that occurred in Iceland. D: No. See the final paragraph. Because of different contexts, we cannot assume the same chain of events would occur in Denali that occurred in Iceland. 32. Explanation: This is a New Information question. A: No. The author does not make this claim in the passage. B: No. This new information would weaken the author’s argument about diversity, not about the occurrence of extinctions in Centinela and elsewhere. The rate of extinction could still be high while the species that were lost are replaced by new species, as in the new information in the question. C: Yes. See paragraphs 1 and 3. If the study outlined in the question stem is accurate, then it would directly contradict the author’s claim. D: No. This answer choice does not directly relate to the study’s claim that the threat of extinction has been exaggerated. 33. Explanation: This is a Weaken question. A: No. The fact that modern hunting methods are more effective does not significantly damage the argument that Paleo-Indians (described as “skilled hunters”) were effective enough to devastate the mammoth population. B: No. As in choice A, this statement is not strong enough to weaken the passage. If saber-toothed tigers sometimes hunted mammoths, this fails to show that humans did not themselves kill a significant number, or that the tigers were the true cause of the extinction. C: Yes. If early American hunters could only kill injured mammoths that would likely have died soon anyway, then we can infer that it is unlikely that hunters “devastated mammoth populations.” D: No. This answer choice is unrelated to mammoths. 34. Explanation: This is a New Information question. A: No. See the explanation for D below. B: No. See the explanation for D below. C: No. See the explanation for D below. D: Yes. If the fossilized forms were found on the same level of rock, it would establish only that the animals and humans perished during the same time period. Without more information, we cannot infer whether they died from “climatic change” or “overkill.” 35. Explanation: 1. All of the following are reasonable methods of protecting individuals with SCID against infection EXCEPT: A. exposing them to only filtered air. B. sterilizing their food. introducing ADA into the bloodstream. D. vaccination. Correct Explanation: D. Individuals with SCID lack an immune response. They must be protected from infectious microorganisms, which could be accomplished by air filtration and food sterilization (A and B are reasonable methods and can be eliminated). The passage described the lack of the enzyme ADA as one cause of SCID and the introduction of ADA into blood as providing a treatment (C is a reasonable method and can be eliminated). Vaccination will not work with an individual with SCID. Vaccination relies on an immune response against the antigen, but SCID individuals have no immune response, so vaccinations of any type will be ineffective (D is false and thus the correct answer choice here). 2. In some SCID patients, gene therapy has been used to introduce the ADA gene into T cells through a viral vector. The most likely explanation for failure of this therapy in some patients is: antibody response against the viral vector. viral vectors cannot be used since patients are susceptible to infections. some patients have no detectable T cells. viruses cannot transcribe mammalian genes. Correct Answer Explanation: C. Lack of ADA can lead to T-cell death and SCID. In some cases of SCID, the passages states, T cells are absent. If T cells are not present, then they cannot be targeted for gene therapy (C is correct). Choice A is incorrect since SCID patients lack a normal immune response. B is wrong since this does not make sense. The failure of therapy would indicate that an inadequate fraction of cells were infected, not that infection occurred with higher than normal efficacy. And D is incorrect; the virus is not expected to transcribe mammalian genes, only to act as the vector that introduces the genes. The failure cannot be ascribed to an effect that was not expected in the first place. 3. Although the results of T-cell gene therapy in SCID patients have been promising, this treatment must be repeated over time. This could be due to the fact that: new T cells are derived from stem cell precursors. mature T cells reside only in the bone marrow. adenosine deaminase induces cell death in T cells. SCID patients have an immune response against their own T cells. Explanation: Correct Answer A. T cells have a finite lifetime in the bloodstream. If a round of gene therapy infects 100% of all T cells in the blood stream, all of these cells will eventually die and be replaced by new cells that are formed from stem cells. The new cells will have the disease, being derived from stem cells that were not treated with gene therapy in the first round since they are not T cells (A is correct). Mature T cells will not be found in the bone marrow for the most part, but in the bloodstream, in lymph nodes, and throughout the body (B is incorrect). Adenosine deaminase relieves the illness, but does not cause it (C is wrong). SCID patients do not have an immune response that would allow them to react against their own T cells (D is wrong). 4. Twenty-five percent of all SCID patients lack an enzyme called adenosine deaminase (ADA). The absence of ADA in T cells causes cell death. These patients can be treated with injection of ADA that is linked to a molecule which makes the enzyme stable in the bloodstream. If the stem cells residing in the bone marrow are defective, then all of the following will be affected EXCEPT: A. erythrocytes. B. platelets. C. immunoglobulins. D. fibrinogen. Correct 5. Intermediate X formed in Experiment 1 displays: A. organometallic properties. B. double-bond formation. C. resonance stabilization. Correct D. formation of a carbocation. Explanation: C. Intermediate X is an enolate ion which is stabilized by resonance. It is formed by deprotonation of the ketone by hydroxide. 6. Competing reactions in Experiment 1 are responsible for the product mixture. All of the following reactions contribute to the product mixture EXCEPT: A. deprotonation. B. aldol condensation. C. nucleophilic substitution. D. electrophilic addition. Correct Explanation: D. Deprotonation (choice A) occurs between the hydroxide ion and 3-pentanone, the starting material. Aldol condensation (choice B) could occur between Intermediate X (an enolate ion) and the starting material. Nucleophilic substitution (choice C) occurs between Intermediate X and methyl iodide. However, electrophilic addition (choice D) could not occur, because the only unit of unsaturation present is the ketone, which is an electrophile, and hence could only undergo nucleophilic addition. 7. In the alkylation step of Experiment 2, the carbon β to the nitrogen acts as: a nucleophile due to partial negative charge from resonance. a nucleophile due to partial negative charge from induction. C. an electrophile due to SN2-type reaction. an electrophile due to an inductive effect. Explanation: Correct Answer A. The carbon β to the nitrogen acts as a nucleophile, because it reacts with methyl iodide, which is an electrophile; this eliminates choices C and D. The partial negative charge on the β carbon is due to resonance, as can be seen most easily by analogy to an enolate ion. 8. Why does removal of H2O in Experiment 3 improve the product yield? Water acts as an acid and reprotonates the enamine. It creates a favorable equilibrium for the forward reaction. Azeotropism lowers the activation energy of the forward reaction. Water hydrogen bonds with the ketone, slowing the reaction rate. Explanation: Correct Answer B. By Le Châtelier’s principle, removal of products from a reversible reaction will drive the reaction toward products. 9. In Experiment 1, several products are formed. One of the reactions, which involves unreacted carbonyl compounds and their conjugate bases, is an example of: A. electrophilic addition. B. nucleophilic addition. Correct nucleophilic substitution, unimolecular. D. nucleophilic substitution, bimolecular. Explanation: B. The only reaction that will occur between unreacted carbonyl compounds and their conjugate bases (enolate ions) is an aldol condensation. An aldol condensation is an example of nucleophilic addition. 10. Which one of the following does NOT have a lower boiling point than piperidine? A. CH4 B. (C2H5)3N (C H ) NH Correct Answer D. (C2H5)2NCH3 Explanation: C. Because diethylamine (choice C) is the only compound of the four given choices that can experience hydrogen bonding, it will have the highest boiling point. Therefore, it is the most reasonable choice to have a higher boiling point than piperidine. 11. Which of the following constituents of oviduct cells would first show increased activity on contact with stilbestrol? A. Golgi bodies B. Mitochondria C. Ribosomes D. RNA polymerase II Correct Explanation: D. Stilbestrol is a compound with estrogenic effects greater than those of estrogen. Estrogen acts by binding to an intracellular receptor that then regulates the transcription of genes by RNA polymerase II, the enzyme responsible for transcription of all mRNAs (D is correct). Ribosomes and Golgi bodies would play a role after transcription, in the translation and processing of proteins (A and C are wrong). Mitochondria are not directly involved in the activity of estrogen or stilbestrol (B is wrong). 12. If radiolabeled stilbestrol were administered to the experimental chicks, stilbestrol would be found most heavily concentrated: at the cell membrane of oviduct tissue. B. in the cytoplasm of oviduct tissue. C. in the nuclei of oviduct tissue. Correct D. in the mitochondria of oviduct tissue. Explanation: C. When stimulated by the addition of a ligand such as stilbestrol, estrogen receptor will localize within the nucleus, where it regulates genes by binding to enhancers and promoters. Radiolabeled stilbestrol would localize with estrogen receptor in the nucleus (C is correct). There is no estrogen receptor in the plasma membrane or mitochondria (A and D are wrong). Some estrogen receptor may be located in the cytoplasm, particularly in the absence of ligand, but it will localize mostly in the nucleus when it has ligand bound (B is wrong). 13. Can young White Leghorn female chicks respond to estrogenic stimulation? Yes, because their weight normally A. increases during the gestational period. Yes, because their oviduct tissue B. enlarges in response to stilbestrol injection. No, because post-pubertal females C. have estrogen-insensitive oviduct tissue. No, because endogenous estrogen is directed toward respiratory, D. digestive, and other nonreproductive functions. Correct Answer Explanation: B. The animals used in the experiment shown in Figure 1 were young White Leghorn chicks. These animals responded to stilbestrol with a large increase in oviduct weight, indicating that these animals can respond to estrogenic stimulation such as that of stilbestrol (B is correct). It is certainly true that chick weight will increase during gestation, but the relation of this to estrogen is not clear (A is wrong). C is not likely to be true: After puberty, estrogen will play a key role in reproduction, and it is likely that oviducts will be regulated by estrogen. There is no information provided about D in the passage, and it is not true. Stilbestrol is only a synthetic compound used in this experiment to mimic the effects that endogenous estrogen would normally produce, of which reproductive functions are particularly important. 14. Extrapolating from Figure 1 above, if an experimental group of 10 chicks were given a daily dose of 0.75 mg of stilbestrol for seven days, and a separate control group of 10 chicks were observed over the same period but given no stilbestrol, average oviduct weights would be approximately: 900 mg for the experimental group and 0 mg for the control group. 900 mg for the experimental group and 75 mg for the control group. 1000 mg for the experimental group and 0 mg for the control group. 1000 mg for the experimental group and 900 mg for the control group. Explanation: Correct Answer B. A stilbestrol dose of 0.75 mg per day would lie midway on the x axis between the 0.5 and 1.0 mg doses. By extrapolating from the x axis to the y axis along the curve, it appears that 900 mg would be the oviduct weight predicted at 0.75 mg/day. One thousand mg oviduct weight is the response observed at 1.0 mg, but it would not be expected at 0.75 mg/day since the curve increases between these points (C and D are wrong). The control group in the graph has less then 200 mg but is not zero, eliminating choice A and leaving B as the answer. 15. In another experiment, female White Leghorn chicks are administered 1.0 mg of stilbestrol for one week in the presence or absence of clomiphene citrate, an estrogen antagonist. Which of the following results would NOT contradict the findings of the first experiment? Clomiphene decreased the average oviduct weight from maximum levels. Stilbestrol decreased the average oviduct weight. Clomiphene has no effect on stilbestrol-induced weight gain. Before stilbestrol administration, the Correct Answer D. test chicks showed maximal levels of weight gain. Explanation: A. If stilbestrol is an estrogen receptor agonist (i.e., has effects like those of estrogen) and clomiphene citrate is an estrogen antagonist, then clomiphene citrate should reverse the increase in oviduct weight that is induced by stilbestrol (A is correct, and C is wrong). Statements B and D contradict the passage since Figure 1 shows that stilbestrol increases oviduct weight. 16. The hyphae found in a lab experiment are protected by a cell wall composed of: A. keratin B. chitin Correct C. peptidoglycan D. phospholipids Explanation: B. One of the characteristics of all fungi is a cell wall composed of chitin (B is correct). Keratin is found in the skin of mammals, peptidoglycan is found in the cell wall of bacteria, and phospholipids are part of the cell membrane and not the cell wall. 17. The structure of (+)-fructose is shown below: How many chiral centers does (+)-fructose contain? A. 1 B. 2 Correct Answer D. 4 Explanation: C. Numbering from the top carbon down, carbons 3, 4, and 5 are chiral centers because they each have four different substituents. 18. A scientist wants to separate a mixture of amino acids in a solution buffered to pH 6.0 by using electrophoresis. The mixture is composed of lysine, glycine, and aspartic acid, which have isoelectric points of 9.7, 6.0, and 3.0, respectively. The expected order of the amino acids I, II, and III is: A. lysine, glycine, aspartic acid. Correct B. lysine, aspartic acid, glycine. C. aspartic acid, glycine, lysine. D. aspartic acid, lysine, glycine. Explanation: A. First, it is clear that glycine will be amino acid II on the electrophoresis gel since its isoelectric point matches the pH of the solution. This eliminates choices B and D. Since opposite charges attract each other, the positively-charged amino acid at pH 6.0 will be amino acid I since it will be attracted to the minus charge. Lysine, with an isolelectric point of 9.7, is the positively- charged amino acid at pH 6.0, so the answer is A. 19. If an organic nerve toxin (acting at the neuromuscular junction) renders the ion channel of postsynaptic acetylcholine receptors permanently open, the toxin would be most likely to: cause prolonged hyperpolarization of the postsynaptic membrane. cause prolonged depolarization of the postsynaptic membrane. block the release of vesicles containing acetylcholine. D. prevent muscle contraction. Correct Answer Explanation: B. The acetylcholine receptor in the neuromuscular junction is a ligand-gated sodium channel. When it binds acetylcholine, it opens to allow sodium to flow down a gradient into the cell, depolarizing the muscle cell. The more that the channel is open, the greater the depolarization (B is correct). Hyperpolarization would require positive charges to leave the cell, not enter (A is wrong). The toxin acts on the acetylcholine receptor, so there is no reason to believe that it will block acetylcholine release (C is wrong). The result of prolonged depolarization will be excessive excitation of skeletal muscle, not a block on contraction (D is wrong). 20. HIV, the virus that causes AIDS, is a retrovirus. Retroviruses have an RNA genome that, after entry into the host cell, is reverse transcribed to DNA, then incorporated into the host genome. RNA copies of the viral genome are produced using the normal host machinery, then packaged into viral capsid proteins for release. Which one of the following is most likely to contribute to the development of drug- resistant HIV? Mutation of the virus after insertion into the host-cell genome Frequent random errors in transcription by host-cell enyzmes Correct Answer Viral proteins folding differently in C. the presence of drug than in its absence Changes in the tertiary structure of viral RNA by drug Explanation: B. Drug resistance develops as mutant versions of the virus are produced and begin infecting new host cells. The change must be able to be passed on to viral progeny. If the viral proteins fold differently in the presence of drug than in its absence, this might account for the mechanism of action of the drug, but does not explain how drug resistance develops, nor could this be a heritable change (choice C is wrong). Changes in the tertiary structure of the viral RNA by the drug is another temporary, non-heritable change (choice D is wrong). Choices A and B are both plausible mechanisms for creating new, heritable versions of the virus. However, mutation of the virus after insertion into the host-cell genome would require that an error in DNA replication be made—a rather unlikely event, given the proofreading ability of DNA polymerase. Viral progeny are produced through transcription (creating a new RNA viral genome off the permanent DNA version inserted into the host-cell genome), and the question states that this occurs using the normal host machinery. Since the normal host RNA polymerases have no proofreading function, it is more likely that errors will occur here, leading to mutant virus (choice B is better than choice A). 21. The loss of net production of ATP during glycolysis that occurred in the presence of arsenate and absence of Pi was due to: A. higher levels of reduced NAD+. B. an absence of reduced NAD+. decreased formation of 1,3- bisphosphogylcerate. Correct Answer D. decreased formation of ADP. Explanation: C. Arsenate competes with Pi as a substrate for glyceraldehyde-3-phosphate dehydrogenase. In the presence of arsenate, 1-arseno-3-phosphoglycerate is produced instead of 1,3-bisphosphoglycerate. 1- Arseno-3-phosphoglycerate then breaks down spontaneously into 3-phosphoglycerate, a normal glycolytic intermediate. It does this without enzymatic catalysis, however, and without producing ATP in the process. The rest of glycolysis proceeds normally from 3- phosphoglycerate, with ATP still produced by pyruvate kinase. Per glucose, the ATP produced at each step in the presence of arsenate and absence of Pi is: –1 Hexokinase –1 Phosphofructokinase 0 Phosphoglycerate kinase (normally +2) +2 Pyruvate kinase The net production of ATP per glucose is zero due to the bypass of 1,3-bisphosphoglycerate production (C is correct). Since the arsenate still acts as a substrate of glyceraldehyde-3-phosphate dehydrogenase in the same manner as Pi, it is likely that the reaction mechanism remains the same and that NADH is still produced (B is wrong). Higher levels of NADH (reduced NAD+) would not be predicted either (A is wrong). ATP production would be decreased, but ADP production would not (D is wrong). 22. Based on Figure 1, what is the net reaction for the transformation of glucose to pyruvate? A. Glucose + 2 ADP2 pyruvate + 2 ATP 2 ADP + 2 Pi + 2 NAD+ 2 ATP + 2 B. NADH + 2 H+ + 2 H2O Glucose + 1 Pi + 1 ADP + 2 NAD+2 C. NADH + 2 H+ + 2 H2O Glucose + 2 Pi + 2 ADP + 2 NAD+2 D. pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O Correct Answer Explanation: D. Choice A is missing NAD+, NADH, Pi, H+ and water. Choice B is missing glucose and pyruvate. Choice C is missing pyruvate on the right side and has the wrong stoichiometry on the left. This leaves choice D, which correctly lists all of the substrates and products in the correct stoichiometry. 23. To produce the maximum number of ATPs, post- glycolytic pathways in aerobes must receive from glycolysis: A. ADP and NADH. B. ATP and NADH. C. NADH and glucose. D. NADH and pyruvate. Correct Explanation: D. The post-glycolytic pathways are the Krebs cycle and electron transport, which require oxygen, NADH, and pyruvate. Pyruvate is converted into acetyl-CoA to enter the Krebs cycle (D is correct). The Krebs cycle does not require either ADP or ATP from glycolysis and does not need glucose, only the pyruvate that is derived from glucose. 24. In glycolysis, how many moles of inorganic phosphate are consumed in the oxidation of 3 moles of glucose to pyruvate, as pictured in Figure 1? A. 1 B. 3 Correct Answer D. 9 Explanation: C. For every glucose molecule, 2 molecules of glyceraldehyde-3-phosphate are produced. Every molecule of glyceraldehyde-3-phosphate requires one molecule of Pi to be converted into 1,3- bisphosphoglycerate. For 3 moles of glucose, 6 moles of glyceraldehyde-3-phosphate are produced, requiring 6 moles of Pi. 25. 26. 27. The glycolytic pathway produces a fructose-1,6- bisphosphate in the D configuration rather than the L configuration, because the glycolytic pathway is stereospecific for: A. D-glucose. Correct B. L-glyceraldehyde. C. L-glucose. D. (R)-glyceraldehyde. Explanation: A. Enzymes are highly stereoselective in the reactions they catalyze, but glycolysis will not change the stereospecificity of substrates. If D-fructose-1,6- bisphosphate is the product, it must be derived from D- glucose. 28. Retinol may be classified as what type of molecule? A. Alkaloid B. Diterpene Correct C. Aldehyde D. Monoterpene Explanation: B. Choice A is incorrect since alkaloids are naturally occurring amines, but retinol contains no nitrogen. Choice C is wrong, because it is retinal that is an aldehyde, not retinol, which is an alcohol. The passage states that β-carotene, a tetraterpene, is split in half to form 2 units of vitamin A. Half of a tetraterpene is a diterpene (B is correct and D is wrong). 29. 30. Opsin and another compound combine by dehydration to yield rhodopsin. The compound that combines with opsin in this step displays: a trans isomerism at one carbon A. because of oppositely positioned hydrogens. a cis isomerism at one carbon because of tautomeric conformation. C. free rotation at carbon 11. a cis isomerism at one carbon because of same side substituents. Correct Answer Explanation: D. 11-cis-Retinal, which is the compound that combines with opsin, has only one cis alkene—at the carbon γ to the aldehyde carbon—so choice D is correct. 31. Retinal isomerase is used to alter the conformation of retinal. Retinal isomerase is most likely manufactured by: A. dehydration synthesis. Correct B. hydrolytic synthesis. C. oxidation. D. glycosidic anabolism. Explanation: A. Retinal isomerase, an enzyme, is a protein, and proteins are synthesized by the condensation of amino acids. Condensation involves dehydration. 32. The amino group in opsin is part of a lysine residue. A highly acidic environment would most likely: prematurely isomerize 11-cis-retinal to 11-trans-retinal. B. decrease solubility of vitamin A. render opsin nonfunctional for rhodopsin formation. render rhodopsin nonfunctional for conversion to opsin and retinal. Explanation: Correct Answer C. Under acidic conditions, the amine on the side chain of the lysine residue of opsin would be protonated. This would prevent reaction with 11-cis-retinal, because when protonated, the amine cannot act as a nucleophile. 33. 34. Respiratory centers in which part of the brain normally send messages to respiratory muscles? A. Cerebellum B. Cerebrum C. Medulla Correct D. Hypothalamus Explanation: C. The respiratory control center in the medulla controls automatic respiration without conscious involvement (C is correct). The cerebellum is involved in coordinating motion, the cerebrum is involved in higher thought, and the hypothalamus integrates nervous and endocrine functions through the pituitary (A, B, and D are wrong). 35. All of the following apply to mitotic prophase EXCEPT: recombination between homologous chromosomes. Correct Answer B. formation of spindle fibers. C. nuclear envelope breakdown. D. condensation of chromosomes. Explanation: A. Both meiosis and mitosis share B, C, and D in common. Recombination only occurs in meiosis, however, and not mitosis (A is false and the correct answer choice here). 36. Unlike humans, in birds the females are the heterogametic gender (produce two different gametes with respect to the sex chromosomes). The sex chromosomes are denoted Z and W, and the W chromosomes carries very little genetic information compared to the Z chromosome. If a sex-linked gene in birds has two different alleles, A and a, that display classical dominance, which of the following represents the possible avian genotypes? A. Females: ZAW or ZaW Males: ZAZA, ZAZa, or ZaZa B. Females: ZAZA, ZAZa, or ZaZa Males: ZAW or ZaW C. Females: ZAW or ZaW Males: ZAW or ZaW D. Females: ZAZA, ZAZa, or ZaZa Males: ZAZA, ZAZa, or ZaZa Explanation: Correct Answer A. Since female birds are the heterogametic gender, their gender genotype must be ZW (choices B and D are wrong), and the male bird genotype must be ZZ (choice C is wrong). The key words are “unlike humans”. 37. In which of the following structures is E. coli most likely to cause infection? A. Trachea B. Bladder Correct C. Small intestine D. Large intestine Explanation: B. The passage states that E. coli only causes disease outside of the intestinal tract (C and D are wrong), in the urinary tract, the biliary tract, and the nervous system in particular. The bladder (choice B) is the best answer since this is part of the urinary tract, mentioned as a potential site of infection. 38. Which of the following structures plays a primary role in homeostatic regulation of ion concentration in E. coli? A. Cell wall B. Lactose vesicles C. Cell membrane Correct D. Nuclear membrane Explanation: C. The cell wall cannot be the key component in regulating ion movement into or out of cells because the cells behave the same without cell walls in Experiment 2 (A is wrong). Bacteria do not possess membrane-bound organelles or vesicles (B and D are wrong). The cell membrane must be the key component in regulating ion flow (C is correct). This is the only choice left, by elimination. It is also the only choice that makes sense: The cell membrane is what regulates the flow of all material into and out of the cell for all organisms. 39 . A bacteriologist initiated an E. coli culture from one E. coli cell and hypothesized that some of the progeny in the culture would be genetically different from the original parent cell. Is this hypothesis true? Yes; bacteria are capable of A. undergoing genetic recombination through a variety of mechanisms. Yes; bacteria reproduce sexually, and the progeny of any one cell are B. genetically distinct from the parent cell. No; bacteria are asexual organisms, and in the absence of mutation, all C. progeny of any one cell are genetically identical to the parent cell. No; bacteria can reproduce only by D. meiosis, which ensures preservation of the genome. Correct Answer Explanation: C. Bacteria reproduce asexually, by one cell replicating its genome and then splitting into two cells that are genetically identical to the original cell. The only potential sources of genetic variation in bacteria are mutation and the transfer of genetic information through conjugation, transduction, or transformation, none of which are linked to reproduction. In the absence of mutation, all progeny of a cell will be identical to the original cell (C is true). Bacteria only perform recombination under special circumstances such as through the presence of Hfr plasmids that replicate a portion of the bacterial genome to make it transiently diploid (A is false). There is no indication of a role for Hfr in this case and in a clonal cell line, it could not play a role. Bacteria do not perform the recombination, independent assortment and independent segregation that create genetic diversity in eukaryotes that reproduce sexually (B is wrong). They also do not perform meiosis (D is wrong). 40. Based on the role that E. coli play in the human digestive tract, which of the following describes the normal relationship between the bacterium and its host? A. Commensalism B. Competition C. Parasitism D. Mutualism Correct Explanation: D. E. coli normally live in the human intestine, where they will receive nutrients from their host and will provide the host with an essential role in digestion. Both organisms benefit from this interaction, making this a form of mutualism (D is correct). If only one organism benefited, the interaction would be commensalism (A is wrong). Parasitism is not the case in the normal interaction (C is wrong), although during an infection it may apply. Competition does not apply in this case: This would indicate that the organisms were both competing for the same resources, which is not the case. 41. Based on the results of Experiments 1 and 2, it is reasonable to assume that all components of the mechanism necessary for concentrating lactose intracellularly within E. coli are located in the: A. rough endoplasmic reticulum. B. genome. C. cell membrane. Correct D. Golgi bodies. Explanation: C. Here, the key experiment is Experiment 2, in which vesicles formed from the cell membrane had the same ability to concentrate lactose as whole cells (C is correct). The genome will encode protein components, but the active components are not themselves physically located in the genome (B is wrong). The ER and Golgi are not found in bacteria (A and D are wrong). 42. If the measurements taken in Step 4 of Experiments 1 and 2 had shown no change in bacterial lactose concentration, then it is likely that within the medium: hydrogen ion concentration had A. remained unchanged in Experiments 1 and 2. Correct Answer hydrogen ion concentration had increased in Experiments 1 and 2. potassium ion concentration had C. remained unchanged in Experiments 1 and 2. potassium ion concentration had increased in Experiments 1 and 2. Explanation: A. These experiments show that a gradient of either potassium or protons can drive the transport of lactose into the cell against its gradient. If there is no lactose transport, it is safe to assume that the concentration in the media of the driving ion will remain the same (A is correct). There is no reason to assume that hydrogen ion concentration would increase (regardless if lactose transport had occurred or not) since this is not the case in any of the experiments (B is wrong). Step 4 involves a proton gradient, not a potassium gradient (C and D are wrong). 43. Amides have two common resonance structures because of the lone pair of electrons on the nitrogen. This allows partial double-bond character between the carbonyl carbon and the nitrogen, significantly restricting rotation. How many peaks would be exhibited in the 1H NMR spectrum at room temperature for ethanamide? A. 2 B. 3 C. 4 D. 5 Explanation: B. The structure of ethanamide is shown below. One resonance will come from the CH3 group. The two hydrogen atoms on the nitrogen are different due to partial double-bond character between the carbonyl carbon and the nitrogen. Two more resonances will result from these two distinct protons. This gives a total of 3 resonances. 44. When an acid chloride undergoes hydrolysis, water functions in what role? A. As an electrophile B. As a Lewis acid C. As a catalyst D. As a nucleophile Correct Explanation: D. In the hydrolysis of an acid chloride, water nucleophilically attacks the carbonyl. 45. How many urea groups are present in a caffeine molecule? A. 0 Correct Answer C. 2 D. 3 Explanation: B. A urea group is a carbonyl carbon bonded to two nitrogens, and caffeine has exactly one such group. 46. Which one of the following molecules contains an amide linkage? A. Linolenic acid B. Chymotrypsin Correct C. Ammonia D. Glucose Explanation: B. An amide linkage is a carbonyl carbon bonded to one carbon and one nitrogen. Neither linolenic acid (a carboxylic acid) nor glucose contains nitrogen, and since ammonia contains no carbon, the answer must be B. Chymotrypsin is a protein composed of amino acids all of which are bonded through amide linkages. 47. Hydrolysis of an acid chloride in an inert solvent which dissolves both reactants renders the rate of hydrolysis similar for various acid chlorides. Hydrolysis in pure water will be slowest for which of the following compounds? A. CH3COCl B. CH3CH2COCl C. CH3CH2CH2COCl CH CH CH CH COCl Correct Answer Explanation: D. Choice D, butanoyl chloride, will have the slowest rate of hydrolysis in pure water because it is the least soluble (due to its long hydrophobic tail) of the given choices. 48. All of the following are components of plasma EXCEPT: A. fibrinogen. B. erythrocytes. Correct C. potassium. D. immunoglobulins. Explanation: B. Plasma is the cell-free portion of blood. Proteins and salts are present in plasma, but cells—such as erythrocytes— are not, by definition. 49. The tertiary structure of proteins is partially due to disulfide bonds between cysteine residues. These bonds can be broken by treatment with a mild reducing agent as shown below: Which one of the following could be such a reagent? A. KMnO4 B. H2SO4 NaBH Correct Answer D. CH3CH2OH Explanation: C. Both KMnO4 (potassium permanganate) and H2SO4 (sulfuric acid) are very strong oxidizing agents, and CH3CH2OH (ethanol) is a poor reducing agent (and also a poor oxidizing agent). The answer must be C, sodium borohydride. 50. Which of the following Newman projections is the most thermodynamically stable conformation of isopentane? Explanation: B. Since choice D is in a higher-energy eclipsed conformation (as opposed to a staggered conformation), it can be eliminated. Of the three remaining staggered conformations, choice B has the least steric hindrance since both A and C have two gauche interactions, and choice B has only one. 51. It was observed under the microscope that a small section of bone consisted of concentric rings of fibrous material surrounding an open circular region. The bone section was identified as an osteon. The circular region is expected to contain: A. mature osteocytes. B. maturing chondrocytes. C. large blood cell precursors. D. blood vessels. Correct Explanation: D. In compact bone, the osteon is the basic unit of structure. Concentric rings surround the central circular region that contains blood or lymph vessels (D is correct). Osteocytes can be found in small spaces along channels branching away from the central channel (A is wrong). Bone is the site of the marrow in which blood cell precursors are found, but bone marrow is found in spongy bone and not in compact bone where osteons are found (C is wrong). Chondrocytes are found in cartilage (B is wrong). 52 . Fungi secrete digestive enzymes directly onto organic matter from which they absorb nutrients. Fungi are good examples of: A. chemoautotrophs B. chemoheterotrophs Correct C. photoautotrophs D. photoheterotrophs Explanation: B. In these descriptions of nutritional requirements, the first portion denotes the source of energy as either chemical (chemo-) or the sun (photo-). Fungi receive their nutrition from chemicals and not the sun (C and D are wrong). Autotrophs use carbon dioxide as their carbon source, while heterotrophs use organic molecule building blocks from other organisms. Fungi absorb a variety of molecules (carbon sources) derived from other organisms making them heterotrophs. They are therefore chemoheterotrophs (B is correct). This is a Primary Purpose question. A: Yes. This choice covers all of the major themes of the passage, without going beyond its scope. In paragraphs 2-4 the author describes and rejects various definitions of literature. In the last paragraph, the author suggests (not definitively claims) that “fine writing” may provide the basis for a more valid definition. B: No. This choice is too narrow; it is limited to paragraph 2. C: No. This choice is an overly extreme version of choice A. The author suggests, rather than explicitly defends an alternative, and fails to describe its specific advantages over other approaches. D: No. This choice is too broad and vague. The passage’s scope is limited to the definition of literature. 36. Explanation: This is a New Information question. A: No. Neither the passage nor the question stem indicates that these novels are examples of fine writing, or how that could be used to define literature. B: Yes. In the passage, the author rejects pragmatism as a useful distinction, in part because some non-pragmatic uses of language (jokes) are clearly not literature. The new information in the question stem gives an example of works that are clearly literature and that have a pragmatic function, and so is directly relevant to that part of the author’s argument. C: No. The author does not make this claim; it contradicts the author’s discussion in the second paragraph. D: No. While the new information is relevant to pragmatic functions, it says nothing about practical uses of literature in other societies (we are not told when or where these historians exist). 37. Explanation: This is a Weaken question. A: Yes. First note that the “functional definition” of literature is that it is non-functional (nonpractical); if novels and plays were read to gain practical information, it would directly contradict this functional definition. B: No. This specific point does not challenge the definition of literature in general. C: No. The fact that not all scholars can agree on a definition does not directly challenge the validity of this particular definition. D: No. This answer choice is not directly related to the “functional” definition of literature. 38. Explanation: This is a Vocabulary-in-Context question. A: Yes. From the context of the sentence, we know the passage equates “ontological” with “the fixed beings of things”; the phrase “inherent qualities” most approximates this definition. B: No. See the explanation for A above. C: No. See the explanation for A above. D: No. See the explanation for A above. 39. Explanation: This is an Inference question. A: Yes. The author asserts that defining literature based on its content is impossible, since almost any written work may be called literature. B: No. The main theme of the passage indicates that although there is no easy way to define literature, there should be a way to define it that sets it apart from other written works; the final paragraph provides examples of works not commonly thought to be literature. C: No. The main theme of the passage argues that there is no easy way to recognize works of literature. D: No. Although there is no easy way to define literature, the author is searching for an accurate way to define it; the author does not imply that no accurate way exists. 40. Explanation: This is an Inference question. A: Yes. See paragraph 4. Jokes challenge the “functional” definition of literature because they are also nonfunctional, but not commonly thought to be literature. B: No. The author rejects pragmatism as a useful distinction. Furthermore, the author suggests that if we were (mistakenly) to use such a distinction, literature would be characterized by an absence of pragmatic uses (paragraph 4). C: No. Careful composition of jokes is not mentioned as a way to make jokes more literary. D: No. See paragraph 4. The author implies that jokes are not literature, but they are nonpractical.