MCAT Diagnostic Test Review

Question 14 Which of the following is NOT a function of the sympathetic nervous system? A. Increased heart rate Increased heart rate is a valid response caused by sympathetic nervous system activation. B. Pupillary constriction C. Vasodilation The SNS causes vasodilation in skeletal muscle to ready the body for "fight or flight" and promotes vasoconstriction to the viscera, slowing down the digestive tract. D. Vasoconstriction The SNS causes vasodilation in skeletal muscle to ready the body for "fight or flight" and promotes vasoconstriction to the viscera, slowing down the digestive tract.

B. Pupillary constriction Activation of the sympathetic nervous system triggers a fight-or-flight response. This includes several physiological responses: pupil dilation, increased rate and force of heart contraction, blood vessel dilation in skeletal muscle and constriction in gastrointestinal organs, and inhibition of peristalsis by the digestive tract. The parasympathetic system has the opposite effect.

11-13 have no passage to refer to

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Questions 28-30 do not refer to a pasage

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questions 16-18 do not refer to a passage

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Question 8 Given passage information, Giardia most likely transports which of the following proteins external to the organism itself? A. cwp3 B. Histone H4 According to the passage, histone H4 is associated with the cwp genes in the nucleus. C. β-(1-3)-N-acetyl-D-galactosamine The passage states that β-(1-3)-N-acetyl-D-galactosamine is a component of the cyst wall. D. ESV According to the passage, ESV is used to modify and arrange cell wall components inside the parasitic cyst. The question asks for a component that is transported outside of the parasite.

A. cwp3 According to paragraph 2, the CWM is "composed of at least 3 cyst wall proteins (cwp1-3)," one of which is cwp3. The CWM is eventually attached to the intestinal cell membrane that the parasite inhabits. This suggests that there must be a mechanism for transporting this protein from the interior of the parasitic cell to the host cell membrane.

Question 4 The structure of lysine is shown below. This molecule is best described as: A. aromatic. Aromaticity requires a ring structure with a conjugated sigma- and pi-bond electron system. Lysine lacks a ring structure entirely. B. polar and basic. C. nonpolar and not aromatic. Lysine has several polar and ionizable functional groups, so it is certainly not nonpolar. D. hydrophobic. Lysine has several polar and ionizable functional groups, so it is certainly not hydrophobic.

B. polar and basic. The structure of lysine is dominated by a single carboxylic acid group (R(CO)OH) and two basic amine (NH2) groups. Therefore, it is best described as polar and basic.

Question 26 How many grams of compound X (MM = 292.81 g/mol) are required to create a 1.5 M solution of the mixture used to test HCN current as shown in Figure 3? A. 0.0075 g This answer results from a miscalculation. B. 1 g This answer results from a miscalculation. C. 2 g D. 6 g This answer results from a miscalculation.

C. 2 g The passage states that 5 mL solutions were used to test HCN currents. 5 mL is equivalent to 0.005 L. The question asks for a 1.5 M solution of compound X, meaning 1.5 mol/L. We are given the molar mass of 292.81 g/mol. Using dimensional analysis and simplifying the numbers, we can calculate the required mass as follows: (1.5 mol/L)(0.005 L)(292.81 g/mol) = (1.5 mol/L)(5 x 10-3 L)(3 x 102 g/mol) = 22.5 x 10-1 g = about 2 g (Note that we rounded 292.81 to 300.)

Question 24 Based on the observed effects, what is the minimum dose of Compound X required to reduce the HCN current to half the normal current? A. 5 x 10-4 μmol This answer results from an incorrect calculation or assumption. B. 1 x 10-2 μmol This answer results from an incorrect calculation or assumption. C. 5 x 10-2 μmol D. 5 x 10-2 mol This answer results from an incorrect calculation or assumption.

C. 5 x 10-2 μmol A closer look at Figure 3 shows that the y-axis represents the inhibition of Ih as a proportion of Ihmax. The question is asking us to find the X dosage that would cut the Ih in half. On Figure 3 we can see that ΔIh/Imax = 0.5 at approximately 10-5 M on the x-axis. The passage tells us that solutions of 5 mL were prepared. To find the number of moles, we simply multiply volume by concentration: 10-5 M x 5 x 10-3 L = 5 x 10-8 mol 5 x 10-8 mol x (1 μmol / 10-6 mol) = 5 x 10-2 μmol

Question 11 What is a likely neurological symptom caused by the toxin's effect on acetylcholine release? A. Tetanus Inhibiting acetylcholine release would not cause the spastic paralysis seen in tetanus. B. Muscle spasms Inhibiting acetylcholine release would not cause repeated depolarization/activation of the muscle. C. Flaccid paralysis D. Nausea Inhibiting acetylcholine release would have no effect on nausea levels, which are controlled by the medulla.

C. Flaccid paralysis By inhibiting acetylcholine release, the toxin interferes with nerve impulses and causes flaccid (sagging) paralysis of muscles. The presence of acetylcholine at the neuromuscular junction is required for skeletal muscle contraction.

Question 9 With which of the following do the arginine side chains found on histone proteins most likely interact? A. Thymine groups on DNA B. Adenine groups on DNA C. Phosphate groups on DNA D. Oxyribose on RNA

C. Phosphate groups on DNA Arginine is a basic amino acid, meaning that it is positively charged at physiological pH. Positive species interact best with negative species, and of the answers listed, only phosphate groups are negatively charged.

Passage 3 (Questions 11 - 15) Understanding and addressing the economic impacts of climate change presents a unique series of problems. The costs and benefits of any activity taken to mitigate the effects of global warming or to adapt to its impacts will inherently be unevenly distributed across nations, sub-national groups, and even generations. Economic policy decision-making is plagued by incomplete information and speculative assessments about the near- and medium-term impacts of climate change effects. Efforts to divert economic resources towards mitigation or adaptation must involve a heavy opportunity cost, with resources being redirected away from other economically salutary activities, possibly from more effective environmentally sustainable initiatives. Key terms: economic impacts of climate change, heavy opportunity cost Contrast: mitigating the effects of climate change vs. adapting to those changes Opinion: author thinks costs and benefits associated with climate change will be unevenly shared and that the analyses are uncertain With the deep uncertainty around these issues, economists and policy-setters are faced with a challenge to traditional decision-making processes. In the classical approach, key steps proceed in a more or less sequential fashion. Analysts start by identifying the nature of the problem to frame the construction of the relevant research. Research allows stakeholders to develop a complete or near-complete understanding of the relevant issues. Any shortcomings in such understanding simply fuel further research. Once avenues of exploration have been exhausted, policymakers can next identify a number of policy options and craft those options into the most optimal policy that is practicable, thereby solving the problem. Cause and effect: uncertainty challenges traditional decision-making processes Opinion: traditional decision-making sequence: ID problem, research, understand issues, implement optimal policy, solve problem Uncertainties surrounding the economic impacts of climate change, led Professor Granger Morgan to advocate for an iterative problem-solving approach. Under this heuristic, the research that follows problem-identification does not provide a full understanding of all relevant issues, but leads to both continued research and implementation of the adaptive policy that is identified as being the most likely to be beneficial. Policy implementation is carried out concurrently with further research, including assessment of the policy's effectiveness. The policy and other identified alternatives are re-assessed in the light of new knowledge and changing circumstances, and the end state is not a comprehensive solution, but a refined or reframed identification of the problem, which iterates back to the initial research step and to the task of identifying the best adaptive policy for moving forward. Key terms: Morgan, iterative problem-solving approach Contrast: unlike the traditional approach, Morgan's approach has simultaneous research and implementation of the best strategy known at the time, ending with a better understanding of the problem, not a solved problem One implementation of this latter approach is a method of risk mitigation borrowed from investment banking called the portfolio approach. Under portfolio theory, the only rational response to decision-making on uncertain terrain is to create a varied array of both possible and implemented responses. That is, policy-setters should advocate for the simultaneous deployment of both mitigation strategies and adaptation strategies in response to climate change and for the use of a number of strategies involving a resilient and diverse economy and insurance hedges spread across all economic sectors and in different regions of the globe. That is, a nation should ensure that some component of its financial resources is allocated to investments in various countries (and indeed, continents). Key terms: portfolio approach Opinion: to manage uncertainty and risk from climate change, decision-makers should use a variety of different approaches and investments Underlying any approach to decision-models or risk-analysis is cost-benefit analysis. Unsurprisingly, even this foundational assumption for fiscal and economic problem-solving has itself come under critical scrutiny. The typical cost-benefit analysis converts various factors into a common monetary unit - typically US dollars - and then seeks to maximize dollars. Critics suggest that climate change is a uniquely disastrous problem that is not susceptible to a simple dollar-based approach to utility, and that the various consequences of global warming should be disaggregated and examined on an individual basis. Thus, even if climate change were to have a "three-billion-dollar cost" to the petrochemical sector of the economy and a "one-billion-dollar cost" in the form of lost biodiversity in subtropical regions, these two numbers cannot meaningfully be compared to each other, and policies relating to these two issues must be separately examined. Contrast: cost-benefit analysis, which converts everything to dollars and then compares them, vs. disaggregated approach, which separates different problems and examines them individually Opinion: author calls the challenge to cost-benefit analysis "unsurprising," suggesting that the author is aware of how climate change is causing all sorts of models and assumptions to be questioned Main Idea: The economic impacts of global climate change create uncertainty that leads some to question typical methods of decision-making and challenge foundational assumptions about economic analysis.

Pasage 3 of CARS with additional information for questions 11-15

Passage 4 (Questions 16 - 20) While the central otherworldly concerns of the Taoist religion have led some commentators to assert that Taoism is a "religion without religious texts," nothing could be further from the truth. The key texts of Taoism may lack the same coherence and historicity of the Talmud or the Qur'an, but there are nonetheless various works that have profound influence, and no small authority among nearly all Taoist sects. Contrast: some think Taoism is a religion without religious texts, the author disagrees Opinion: author concedes that Taoist texts lack the coherence and historicity of the Talmud and the Qur'an It goes without saying that the Tao Te Ching is the central work of all Taoist religion. Despite two and a half millennia of debate over its origins, authorship, and date of origin, it remains the foundational work of Taoist philosophy and a central component of Taoist ritual. So important is this work that even commentaries on it (themselves many hundreds of years old) have become important religious texts themselves. Opinion: author asserts that the Tao Te Ching is the central work of Taoism Cause and effect: the Tao Te Ching is so important that even later works that were commentaries on it developed into being religious texts in their own right If the Tao Te Ching lays down the foundational ideas of Tao and Te themselves, the practical application of these ideas in life is more fully explored in the Zhuangzi and the I Ching. The Zhuangzi, much like the Tao Te Ching, has an ancient origin (ca. 400 AD) shrouded in no small amount of legend. Supposedly written partly by Zhuangzi himself and later expanded by his disciples, the work eschews the abstract poetry of the Tao Te Ching. Instead, it uses more down-to-earth parables and short dialogues to help readers bring their lives into alignment with the concept of tzu-jan, or naturalness, in their daily lives. It also encourages following the Tao of the elements. Contrast: the Tao Te Ching lays down the basic ideas and uses short abstract poetry but the Zhuangzi is more practical and uses stories Unlike the Zhuangzi, or any other Taoist text, the I Ching predates the Tao Te Ching by centuries. The system of fortune-telling described in the I Ching dates to somewhere in the 12th century BCE. The I Ching is meant to guide practitioners in choosing the right action based on some understanding of the current situation and the future. Early in Taoist development, Taoist scholars adopted the I Ching as their own and advocated it as a central text through which one could meditate on the right way. The cosmological notions at the foundation of the I Ching became so intermingled with Taoist cosmology and Yinyangism over time that by the 16th century there was no meaningful distinction for most practitioners. Contrast: the I Ching is the one text that predates the Tao Te Ching as opposed to all other Taoist works Cause and effect: the intermingled cosmologies of Taoism, the I Ching, and Yinyangism have created a single worldview with most practitioners seeing no distinction between these three schools of thought Finally, in addition to these three core texts, scholars in the fourth and fifth centuries AD attempted to collate all major texts, commentaries, manuscripts, and apologies into a single collection. This work came to be known as the Tao Tsang, typically translated as "Treasury of Tao" or "Taoist Canon." The Tao Tsang was collected and re-collected many times over the centuries but scholars generally recognize four major Tao Tsangs. The first, compiled circa 400 AD, consisted of a bit more than a thousand scrolls and developed the tripartite division that would remain through future efforts. The second and third Tao Tsangs expanded the collection to nearly 5000 separate scrolls, and the fourth and final Tao Tsang of 1444 in the Ming Dynasty settled the compilation at just under 5300 works. Key terms: Tao Tsang Cause and effect: the effort of scholars to collect all Taoist writings in one place led to the creation of the Tao Tsang The Tao Tsang (all four major compilations) divides its constituent works into three broad categories, typically termed "grottoes," each of which is split into a dozen chapters. The three grottoes are concerned with meditation, rituals, and exorcisms, with meditation always considered the highest and most pure set of writings. When someone is working to be initiated as a Taoist master, the grotto of meditation includes the writings used in the final phase of training. Key terms: grottoes, meditation, rituals, exorcisms Contrast: the grotto of meditation is seen as higher and more pure than the others Main Idea: Taoism is a religion with many religious texts, including the core works of the Tao Te Ching, the I Ching, and the Zhuangzi, and collections of lesser writings known as the Tao Tsang.

Passage 4 of CARS with additional information for questions 16-20

Passage 5 (Questions 21 - 25) If a drug company could take all of the positive effects of exercise and put them into a pill, they'd be the most successful company in history. It is, in fact, nearly impossible to overstate the positive effects that regular exercise has on nearly every facet of the body's physiological and the mind's psychological state. Exercise has been demonstrated to not just slow the progression of, but to reverse, many of the symptoms of type 2 diabetes, heart disease, high cholesterol, and hypertension. It can delay the onset of dementia, reduce symptoms of anxiety and depression disorders, and aid in smoking cessation programs. Cause and effect: exercise has tons of benefits for body and mind And yet when patients meet with their physicians, the overwhelming majority of primary care doctors fail to discuss the importance of exercise with patients. To the extent that the topic is discussed at all, the doctor will make, at best, passing remarks about the importance of an exercise program. Even more perversely, there is a strong correlation between lower economic class and decreased likelihood of physician-recommended exercise programs, despite the even stronger correlation between lower economic class and many of the diseases that exercise would most directly benefit (most notably obesity and type 2 diabetes). That is to say, those patients who most need regular exercise are the ones least likely to have a doctor that strongly recommends such a program. Opinion: author thinks that doctors are failing to adequately discuss exercise with patients Contrast: patients of lower economic class vs. patients of higher economic class - the lower economic class patients are more likely to need regular exercise but are less likely to have a doctor who pushes it Why this connection exists is still somewhat unclear, although research is slowly shedding light on the topic. Fundamentally, public health scientists examine two different facets of the correlation: patient-sided factors and healthcare provider-sided factors. Thus, working and lower class patients may not have access to the kind of doctors that will recommend exercise, or doctors may change how they treat patients based on perceived economic class. Cause and effect: factors relating to both patients and doctors influence the frequency of doctor-patient discussions about exercise To date, research seems to suggest both of these factors work in concert. In a groundbreaking study at the University of Arizona College of Medicine, experimenters created audio recordings of over 5,000 patient-physician interactions for patients that were classified as obese. The patient population was categorized into three broad categories of economic class based on income. Researchers found that physicians were 22% more likely to discuss exercise regimens with the high-class patient group than the lowest, and that when exercise was discussed, doctors spent a staggering 420% more time in conversation about exercise with the high economic class group than either the middle or low class group. Despite these stark findings, the researchers' failure to control for factors of ethnicity and gender have created large enough concerns about methodological validity to lead some critics to dismiss the study entirely. Contrast: doctors were more likely to discuss exercise with the rich patients and discussed exercise for a much longer time with these patients than those of a lower economic status Opinion: critics dismiss the results because they think the design of the study was flawed More promising are results obtained from examining the patient-sided factors, including frequency of patient-initiated discussions about exercise programs and patient access to high quality primary care. Here, surveys of both patients and healthcare workers have demonstrated a strong correlation between a patient's economic class and their likelihood of initiating a conversation about exercise with their healthcare provider. This correlation seems to exist regardless of the health status of the patient, and any similarities between the patient and provider in terms of demographic categories. The findings suggest, perhaps, that patients from higher economic classes are simply more comfortable initiating conversations with their healthcare professionals. Cause and effect: patients from higher economic classes are much more likely to initiate conversations about exercise with their doctor Opinion: author speculates that the richer patients are just more comfortable starting conversations with doctors in general A final irony was revealed in the most recent major study published on the topic, which found no correlation between a patient's ability to start and stick with an exercise regimen and how frequently such programs were discussed with healthcare professionals. Contrast: even when doctors discuss exercise more frequently with patients, that doesn't seem to have any effect on patients actually sticking with exercise plans Main Idea: Exercise has huge benefits for both body and mind and yet doctors generally fail to address this important idea, and this failure is even more pronounced when looking at doctor-patient interactions for patients from lower economic classes

Passage 5 of CARS with additional information for questions 21-25

Passage 1 (Questions 1 - 5) CARS About his friend Ludwig Wittgenstein, the Finnish philosopher Georg Henrik von Wright said that Wittgenstein's ideas were "distorted even by those who professed to be his disciples." This misunderstanding of his work and distortion of his ideas may, in some sense, at least partially be Wittgenstein's fault. In the course of his philosophical career he published only a single small book: the Tractatus Logico-Philosophicus. It was not until after Wittgenstein died in 1951 that his various manuscripts were edited together into the lengthy Philosophical Investigations. Key terms: Wittgenstein, Wright, Tractatus, Philosophical Investigations Cause and effect: the misunderstandings or distortions of Wittgenstein's ideas were most likely due to his relatively minor publishing output Wittgenstein's somewhat unusual career as an academic was paralleled by an even more troubled and unusual personal life. After being born to a very wealthy family, Wittgenstein gave away nearly his entire personal fortune, first in large sums to several unknown poets and painters, with the remainder being given to his siblings. The youngest of nine siblings, Wittgenstein's early life was defined by the harsh authoritarianism of his father and the successive suicides of three of his older brothers. Opinion: author thinks Wittgenstein's career and personal life were both unusual and troubled Cause and effect: Wittgenstein's early life was defined by his strict father and his brothers' suicides As a young adult, Wittgenstein's academic career began with him studying mechanical engineering in Berlin. This interest grew into a study of aeronautics, with Wittgenstein even being granted a patent for a particular propeller design. As he continued his engineering studies, he eventually came upon works on the philosophy of mathematics written by Bertrand Russell and Gottlob Frege. These works created a near-obsession with logic and mathematics in Wittgenstein that eventually led Wittgenstein to Cambridge where he studied under Bertrand Russell. Cause and effect: Wittgenstein began in engineering but was turned on to philosophy by the works of Russell and Frege Wittgenstein's studies had their first major interruption due to the outbreak of World War I. After volunteering in the Austro-Hungarian army, Wittgenstein was wounded in an explosion and, near the end of the war, captured by Allied forces and held in a POW camp for nine months. Near the end of the decade, Wittgenstein was rocked by several major setbacks: his dear friend (and likely his lover) David Pinsent was killed in a plane crash, his favorite uncle passed away, and the German publishing house to which he had submitted the Tractatus Logico-Philosophicus declined to publish the work. Cause and effect: Wittgenstein's career had many interruptions, including injury during WWI, difficulty getting his work published, and the loss of two loved ones This combination of personal and professional setbacks derailed Wittgenstein's work for some time. He took work as a gardener in a monastery and later worked as a teacher for schoolchildren in a remote rural village. In an ironic twist given his own upbringing, he became infamous in the village for his near-tyrannical approach to teaching, especially among those students with no knack for math or logic. He used corporal punishment routinely on both male and female students, and used to openly criticize both the village priest and the school headmaster in front of the students. Cause and effect: the various interruptions mentioned in the prior paragraph knocked Wittgenstein off course for awhile and lead to him working as a gardener and elementary schoolteacher Opinion: the author thinks that Wittgenstein ending up as a strict teacher is ironic given his upbringing Several more years passed with Wittgenstein moving between various low-level teaching positions, during which time a "pirate copy" of the Tractatus was published. The work was widely distributed in philosophical circles and created a growing fame for Wittgenstein among Europe's intelligentsia. He eventually returned to Cambridge to teach. Despite having been denied a Bachelor's degree some decade and a half prior, the faculty at Cambridge chose to award him a PhD, viewing the Tractatus as his doctoral dissertation. Cause and effect: the distribution of a pirated copy of the Tractatus developed Wittgenstein's fame to the point where he was able to return to Cambridge as a professor Somewhat surprisingly, the biggest disruption to European life of the past two centuries (World War II) actually had the smallest impact on Wittgenstein's work. As he had been awarded a professorship by Cambridge, it was a relatively simple matter for him to obtain UK citizenship and continue his teaching and writing throughout the war, while most of his family was able to emigrate to the US. Opinion: the author believes that WWII was the biggest disruption in European life but that it had little effect on Wittgenstein and his work Main Idea: The Austrian philosopher Ludwig Wittgenstein had a personal life and professional career that were both unusual and troubled, marked by difficulties and interruptions throughout.

passage 1 of CARS with additional information for questiosn 1-5

Passage 2 (Questions 6 - 10) physics and bio Electrospinning is a technique used by industries in order to produce filters, membranes, and tissue scaffolds for implants. Electrospinning occurs when the electric forces at the surface of a polymer solution overcome the surface tension and cause an electrically charged jet to be ejected. The solvent evaporates as the jet travels in air, leaving behind charged polymer fibers that lay themselves randomly on a metallic electrode (collector). Key terms: electrospinning, surface tension, polymer fibers Cause and effect: when the electrical forces are larger than the surface tension, the droplet can escape the needle and lay down fibers Fibers obtained may have diameters ranging from 0.05 to 5 µm. The small diameters provide high surface area-to-volume and high length-to-diameter ratios. The process has applications in providing scaffolds for tissue engineering products. Key terms: fibers, 0.05 to 5 µm Cause and effect: small fiber diameter creates high surface area-to-volume and length-to-diameter ratios Figure 1 shows a diagram of the apparatus for electrospinning The density, conductivity, surface tension, viscosity, and pH of the solution are controlled prior to electrospinning. Density is measured by determining the mass of a known volume of solution. These fibers can also be coated with proteins as a method of introducing biological molecules to the woven matrix. The encapsulation efficiency ε is determined by Equation 1: E=Mm/Me Key terms: encapsulation efficiency Cause and effect: coating fibers with proteins creates a matrix with biological molecules embedded Equation 1 shows that encapsulation efficiency rises with the mass of the proteins incorporated into the fibers Mm represents the measured mass of the proteins integrated with the fibers constructed, and Me is the theoretically expected mass of the proteins integrated with the fibers. Furthermore, the productivity, Ψ, of the process is calculated using Equation 2: Y=E/Atspin Here A is the total area of the fibers and tspin is the spinning time. Key terms: productivity Equation 2 shows that productivity is inversely related to spinning time and total area; if we combine equations 1 and 2 we see that productivity is inversely related to theoretically expected mass of proteins integrated with the fibers and is directly correlated with the measured mass of proteins integrated with the fibers An experiment was performed on 3 different fibers to determine their mechanical properties. A 10 N initial load and a stress rate of +0.5 N/second were used. Results of the experiment are shown in Figure 2. The Young's modulus was calculated by analyzing the peak stress that the sample was able to endure without deforming. Key terms: experiment, mechanical properties, Young's modulus Figure 2 Results of a mechanical stress test performed on 3 fiber samples Figure 2 shows that fiber C is the strongest fiber

passage 2 with additional information for 6-10 physics/bio

Question 2 (p/b) Tolazamide is an aromatic drug with a similar sulfonylurea structure to glipizide. Which of the following is most likely tolazamide? A. B. This molecule has a carbamic acid in place of the urea group. C. This molecule has no urea group. In its place is a hydroxyl group attached to a nitrogen atom. D. This molecule is not aromatic.

A. First, note that the question stem mentions that tolazamide is aromatic. This eliminates choice D, which lacks conjugation, a characteristic necessary to confer aromaticity. Next, the passage states that glipizide is a sulfonylurea antidiabetic drug. As its name implies, a sulfonylurea compound contains both sulfonyl and urea groups. If tolazamide has a similar structure, it would likely have those same functional groups.

Question 25 How many chiral carbons are present in compound X? A. 0 B. 1 This is incorrect. Compound X has no chiral carbons. C. 3 This is incorrect. Compound X has no chiral carbons. D. 5 This is incorrect. Compound X has no chiral carbons.

A. 0 A chiral carbon is a tetrahedral atom that has four different substituents. There are no such carbons in compound X.

Question 22 Which of the following studies would provide the best evaluation of the author's speculations at the end of the fifth paragraph? A. A study examining how frequently patients ask physicians about medications other than the ones initially recommended by the doctor B. A cross-sectional study that correlates ethnicity and gender with frequency of implementation of doctor-recommended exercise plans This study would be assessing factors discussed in paragraph four, not five. C. A survey asking patients how many members of their immediate family are healthcare workers that specialize in exercise-based fields such as physiatry or physical therapy While someone might be more likely to initiate a conversation about exercise if they are regularly exposed to family members who are focused on the topic, that connection is not definite. This study just doesn't relate closely enough to the issue of being comfortable initiating conversations with healthcare providers in general. D. A longitudinal study that follows three different groups who are given three different doctor-prescribed exercise regimens to determine whether they are able to stick with the plan and if not, why not This choice relates to the facts discussed in the sixth paragraph.

A. A study examining how frequently patients ask physicians about medications other than the ones initially recommended by the doctor The author speculates that patients in higher economic classes are simply more comfortable initiating conversations with healthcare professionals. If this is the case, we should be able to study how often patients initiate conversations on topics other than exercise regimens. Specifically initiating a conversation about alternative medications would be one such example.

Question 13 Which molecule could be used to detect toxin D in the cultures described in the passage? A. An antibody To recognize the antigens on the botulinum protein, an antibody could be used. Antibodies are built to recognize and bind specific proteins. B. A phospholipid Phospholipids are largely hydrophobic molecules that contain long alkyl chains. They would not interact or bind with the target proteins. C. A radiolabeled thymine Radiolabeled thymine would be useful in identifying nucleotides, but not for identifying proteins. D. An antigen Antigens are surface proteins that serve as identifying markers on cells and molecules. They interact with antibodies and would not be able to bind or isolate the toxin. Do not confuse antibodies with antigens!

A. An antibody To recognize the antigens on the botulinum protein, an antibody could be used. Antibodies are built to recognize and bind specific proteins.

Question 16 Which of the following best characterizes the author's attitude towards the position the Tao Te Ching holds among Taoist texts? A. Assurance of its foremost position B. Tentative belief of its status as the least important text This is the opposite of the correct answer, as the Tao Te Ching is the central Taoist text. C. Studied agnosticism about its relative position The author doesn't hold back on an opinion here, making agnosticism an inappropriate choice. Remember, if an author holds a strong opinion about the question topic, neutral answers are relatively unlikely to be right. D. Ignorance about how it relates to other texts The author doesn't hold back on an opinion here, making ignorance an inappropriate choice. Remember, if an author holds a strong opinion about the question topic, neutral answers are relatively unlikely to be right.

A. Assurance of its foremost position The author tells us at the start of the second paragraph that it "goes without saying" that the Tao Te Ching sits as the central work among Taoist texts. If the author thinks it so obvious that it "goes without saying," this suggests absolute assurance on his part that it is the central or foremost book.

Question 15 The symptoms of botulinum took 12-18 hours to be observed in the patient. How is this best explained? A. Growing bacteria produce the toxin. B. Botulinum toxin is immediately filtered by the kidneys and excreted. If the toxin were immediately filtered and excreted by the kidneys, the symptoms would not appear. C. Toxins can be absorbed through mucous membranes or respiratory tract. This is a true statement, but it does not explain why the toxin's initial effect takes so long to manifest. D. Most of the toxins are polar and they take time to cross the nuclear membrane. The toxin has its effect on the neuromuscular junction and does not cross the nuclear membrane.

A. Growing bacteria produce the toxin. If growing bacteria produce the toxin, then it will take time for the bacteria to generate sufficient quantities of the toxin to cause illness.

Question 4 The author's description of Wittgenstein's teaching style as an "ironic twist" (paragraph 5) assumes which of the following? A. Having been raised by a strict authoritarian father, one would have expected Wittgenstein himself to react by forming a more easygoing, laid-back teaching style. B. Children who are raised in a harsh environment end up reproducing that harsh environment when they grow up. This is the opposite of the correct answer. If this were true, then Wittgenstein's own "near-tyrannical" style would be expected, not a twist. C. Philosophers generally make for ineffective teachers. The passage never says or suggests anything about Wittgenstein's effectiveness as a teacher. It merely states that his style was particularly harsh. D. Among wealthy European families, it was expected at the time that children would adopt both the personality style and vocation of their parents. This is the opposite of the correct answer. If this were true, then Wittgenstein's own "near-tyrannical" style would be expected, not a twist.

A. Having been raised by a strict authoritarian father, one would have expected Wittgenstein himself to react by forming a more easygoing, laid-back teaching style. An ironic twist suggests that the author thought that the outcome was different than one would have expected. Since the outcome was that Wittgenstein was a strict teacher, describing this as a "twist" suggests that the author would have expected Wittgenstein not to be strict. This choice presents a logical reason why the author may have held that expectation.

Question 29 Modern MRI machines use electricity to generate their magnetic fields inside a circular chamber instead of using permanent magnets. Which of the following would NOT increase the strength of the MRI field? A. Increased radius of the MRI chamber B. Increased power supplied to the MRI machine Remember, electrical power = IV. Increased power indicates an increased supply of current or energy to the device, which will raise field strength. C. Decreased resistance of the MRI machine This change involves increased current (remember V = IR). Thus, it would increase magnetic field strength. D. Increased current through the MRI machine This change involves increased current (remember V = IR). Thus, it would increase magnetic field strength.

A. Increased radius of the MRI chamber The magnetic field strength generated at the center of a circuit loop is given by B = µoI/2r, where B is the field strength, µo is the permeability of space (a constant), I is the electrical current through the circuit, and r is the radius of the loop. Field strength is directly proportional to current and inversely proportional to radius. Increasing the radius of the chamber will lower the strength of the field at the center of the chamber.

Question 27 Which molecule is least likely to be able to travel via the macula communicans pathway? A. Insulin B. Cl- Cl- is an ion and will be able to move through the channels described in the passage. C. Na+ Na+ is an ion and will be able to move through the channels described in the passage. D. Lysine Amino acids, like lysine, are small molecules that will be able to move through the channels described in the passage.

A. Insulin In paragraph 3, the passage states that this system is devoted to the movement of ions and fluids. Insulin, a peptide hormone, would be too large to use this pathway.

Question 23 Compound X and lidocaine can be separated using ether extraction because: A. Lidocaine is lipophilic while compound X is hydrophilic. B. Compound X is lipophilic while lidocaine is hydrophilic. Lidocaine is not hydrophilic. C. Both molecules are hydrophobic with only nonpolar groups. Both molecules contain polar and nonpolar groups. D. Lidocaine is hydrophilic while compound X is hydrophobic. Compound X is not hydrophobic.

A. Lidocaine is lipophilic while compound X is hydrophilic. "Lipophilic" refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and nonpolar solvents such as hexane. The axiom that "like dissolves like" generally holds true. Thus, lipophilic substances tend to dissolve in other lipophilic substances, while hydrophilic (H2O-loving) substances tend to dissolve in water and other hydrophilic solvents. Lidocaine has a large, nonpolar aromatic ring, alkyl groups, and a few polar groups (the carbonyl, 2 amino groups), so it will be lipophilic (i.e. hydrophobic) overall. Compound X has a charged group, along with several polar amino groups. This makes compound X hydrophilic. Charged species are virtually always more polar than similar uncharged molecules.

Question 9 If all other factors are held constant, which of the following scaffolds would have the highest productivity? A. Me = 1 mmol B. Me = 2 mmol Before examining any equations, we can reason that the highest productivity would result from either the smallest or largest Me of our options, not an intermediate value. This logic allows us to eliminate this answer choice. C.Me = 3 mmol Before examining any equations, we can reason that the highest productivity would result from either the smallest or largest Me of our options, not an intermediate value. This logic allows us to eliminate this answer choice. D. Me = 4 mmol See the correct answer explanation for why the scaffold with the lowest Me, not the highest, would have the largest productivity.

A. Me = 1 mmol Equation 2 shows that productivity is directly proportional to efficiency and inversely proportional to area and spin time. Combining the equations, we see: Y=Mm/Me/ATspin=Mm/MeAtspin Here, we can see that productivity is inversely proportional to Me. To obtain the largest productivity, we want the lowest Me.

Question 22 In vivo, PO43- molecules utilize proton-coupled transport mechanisms to enter the cell. Which statement explains why this is necessary? A. PO43- is hydrophilic. B. PO43- is hydrophobic. Phosphate is charged and polar; it is not hydrophobic. C. The cell membrane is hydrophilic. The phospholipid bilayer of the cell membrane is hydrophobic across its center, which prevents polar or charged molecules from freely crossing. D.The secondary active transport mechanism conserves ATP. Secondary active transport does allow a cell to utilize other forms of energy to transport molecules, but this does not explain why the phosphate must take this route.

A. PO43- is hydrophilic. The structure of phosphate shows it to be negatively charged and polar, which makes it hydrophilic. Thus, it cannot cross the hydrophobic interior of the membrane.

Question 24 The passage author would be most likely to agree with which of the following assertions? A. Patients in the lowest economic classes are just as likely to be able to stick with a doctor-recommended exercise plan as patients in the highest economic classes. B. A female doctor is more likely to discuss an exercise regimen with an obese female patient of lower economic class than a male obese patient from a higher economic class. This contradicts the passage, which states that doctors are more likely to discuss exercise with higher-class patients. C. The positive effects of exercise are overwhelming in the scope and profundity of effect on physiological conditions but are very limited on psychological ones. This contradicts the first paragraph, which tells us that exercise helps both mind and body. D. Had the study described in paragraph 4 been conducted at a different institution, the researchers would have been more likely to use more robust controls. Nowhere does the author state or suggest anything about the particular institutions that are carrying out the studies in the passage.

A. Patients in the lowest economic classes are just as likely to be able to stick with a doctor-recommended exercise plan as patients in the highest economic classes. At the very end of the passage, the author tells us that there seems to be no correlation between how frequently doctors discuss exercise plans and whether patients will stick to such plans. Since there's no correlation, we may guess that patients from a low economic class (who experience few doctor conversations about exercise) and those from a high economic class (who participate in many exercise-related conversations) are equally likely to be able to stick to an exercise plan.

Question 19 In vitro, free oligonucleotides, such as mRNA transcripts, have a short half-life in the cytosol. What mechanism is used to stabilize these molecules? A. Polyadenylation B. Phosphorylation By definition, nucleotides are already phosphorylated. When the PO43- group is removed, the molecules are called nucleosides. C. Enzymatic digestion This is the opposite of what the question is asking, as degradation would lead to a faster breakdown. D. Active transport across the nuclear membrane Active transport across the nuclear membrane would not stabilize an mRNA transcript.

A. Polyadenylation The poly-A tail is important for the nuclear export, translation, and stability of mRNA. The tail is shortened over time, and, when it is short enough, the mRNA is enzymatically degraded.

Question 14 At which nucleophilic site is serine most likely to be acylated by penicillin? A. Side chain OH B. Carbonyl carbon A carbonyl carbon would more properly be thought of as electrophilic. The question asks about a nucleophilic site. C. Carbonyl OH The carbonyl OH is a possible nucleophile, but its proximity to the carbonyl group makes it more sterically hindered than the side chain OH, reducing its ability to interact with penicillin. Also, the resonance stabilization conferred in this carboxylic acid makes its -OH group relatively less nucleophilic than a typical alcohol. D. Alpha carbon The carbon adjacent to the carbonyl carbon is not nucleophilic and would also be sterically hindered from significantly interacting with penicillin.

A. Side chain OH Good nucleophiles are electron-rich species. The likely nucleophile would also need to minimize steric hindrance to be acylated by penicillin. The side chain hydroxyl group fits both of these criteria.

Question 21 A scientist concludes that the phosphorylated β-catenin is the form that is degraded. Why do the experimental results support this conclusion? A. The levels of nuclear 32P decrease faster and remain lower than 32P levels in the cytoplasm. B. The levels of nuclear 32P increase over time while cytoplasmic 32P levels decrease. Figure 1 shows levels of both cell mixtures decreasing over time. C. Cytoplasmic and nuclear levels of 32P both decrease over time. This is observed in the results, but it is the contrast between levels in each location that signifies where the phosphorylated β-catenin ends up. D. Cytoplasmic levels of 32P remain constant. This is not shown by the experimental results.

A. The levels of nuclear 32P decrease faster and remain lower than 32P levels in the cytoplasm. Figure 1 shows that the levels of radioactive P drop off for both cell mixtures. However, 32P activity drops off sooner and nearly reaches 0 in the nuclear extracts. Paragraph 3 states that intact β-catenin accumulates in the nucleus, implying that β-catenin is degraded in the cytoplasm and that there is a mechanism for moving β-catenin between the nucleus and the cytoplasm. Since the nucleus accumulates intact β-catenin (as indicated by the passage) that is non-phosphorylated (as indicated by the drop-off in radiolabeling activity, in contrast to the steady state that seems to be reached in the cytoplasm), it can be concluded that phosphorylated β-catenin is degraded.

Question 16 Which of the following must be true if the penicillin-serine reaction "locks" in the ester formation as described in the passage? A. The thermodynamic cost of breaking the penicillin-serine ester is larger than the thermodynamic release of amide formation. B. The thermodynamic release of forming an amide is equal to the thermodynamic cost of forming an ester. If forming either the ester or the amide were equally favorable, then the system would be in an equilibrium. This wouldn't stop the bacteria from still moving forward with cell wall formation (although it might slow down a bit). C.The thermodynamic cost of breaking the penicillin-serine ester is smaller than the thermodynamic release of amide formation. If the cost to break open the penicillin-serine ester were small, then the molecules wouldn't be locked into that ester configuration. D. The thermodynamic release of forming the penicillin cyclic amide is larger than the thermodynamic release of breaking the penicillin-serine ester. If this were true, the reaction would favor formation of the amide, rather than formation of the ester.

A. The thermodynamic cost of breaking the penicillin-serine ester is larger than the thermodynamic release of amide formation. The passage tells us that once penicillin forms an ester with serine, it prevents the further reactions by the enzyme because the serine residue is now locked into the ester with penicillin. For this to be the case, the ester must be stable. It must be so stable that breaking it apart would be too "expensive" - or too hard to do given the subsequent thermodynamic release that would occur from amide formation.

Question 20 Given the locations of the MlyI cleavage site and recognition sequence, MlyI is NOT a: A. Type I restriction enzyme. B. Type II restriction enzyme. Type II enzymes cleave within or at short specific distances from their recognition sites and often require magnesium. C. Type III restriction enzyme. Type III enzymes cleave at sites a short distance from their recognition sites and require ATP (but do not hydrolyze it). S-adenosyl-L-methionine stimulates this reaction, but is not required. D. Type IV restriction enzyme. Type IV enzymes target modified (e.g. methylated, hydroxymethylated) DNA.

A. Type I restriction enzyme. A restriction enzyme is an enzyme that cuts DNA at or near specific recognition nucleotide sequences, known as restriction sites. Type I enzymes cleave at sites remote from the recognition site; they require both ATP and S-adenosyl-L-methionine to function. Since the passage shows a cleavage site very near a recognition site, MlyI must not be a Type I enzyme.

Question 9 In 2006, despite a substantial technocrat majority among the Mexican senate, leftist parties modestly increased their share of senate seats at the expense of the IRP. Given the information in the passage, this result was probably due to: A. concerns about the competitiveness of the regional economy in several large Mexican states. B. a large-scale shift in party loyalty among IRP members. Based on the passage discussion and the fact that the question says "modestly increased," such a large-scale shift in loyalty is highly unlikely. C. low voter interest in the campaign. The passage does not discuss or imply low voter interest as a factor in elections. If anything, this could cause a decrease in leftist seats. D. a lack of pressing domestic issues facing Mexico. The passage mentions "impact of economic and domestic policy issues" as a force that can cause defection, but there is no information in the passage to suggest that a "lack of pressing domestic issues facing Mexico" might cause members to forego party loyalty.

A. concerns about the competitiveness of the regional economy in several large Mexican states. This question begins with a scenario outside the scope of the passage and asks you to understand or explain it in light of passage information. The scenario presented is similar to the defection mentioned in paragraphs 4 and 5, when the author talks about factors that led to members leaving the IRP party. These paragraphs mention the "impact of economic and domestic policy issues, foreign policy, and especially local economic changes," among others, that might have influenced the defection. This choice best relates to the "economic" aspect of this description

Question 1 The catalyst for TGFβ production most likely plays a direct role in: A. gene silencing. B. ribosomal inactivation Nothing in the passage suggests that HDAC1 has any effect on ribosomes. This is also seems unlikely, since HDAC1 must be found in the nucleus (where it acts on histones), but ribosomes are found outside the nucleus. C. transfer of an acetyl group from acetyl-CoA. When HDAC removes the acetyl group from lysine residues, it is transferring that group to CoA. D. gene activation. Histone acetylation, not deacetylation, would allow for increased gene expression.

A. gene silencing. The passage states that HDAC1 catalyzes the production of TGFβ and acts to remove acetyl groups from lysine residues of histones. This is important to gene regulation because DNA is wrapped around histone proteins, and DNA expression is regulated by the addition and removal of acetyl groups. Deacetylation attracts DNA to histones more tightly, inhibiting transcription. In summary, histone acetylation generally serves to increase gene expression, while deacetylation, along with DNA methylation, acts to silence gene expression.

Question 14 When faced with economic costs due to a failing school system and a poorly managed fire department, the critics mentioned in the final paragraph would most likely advocate for which of the following? A.Examining each issue separately and arriving at a policy decision appropriate for each issue B. Developing a monetary comparison between the two situations and solving the more expensive one first This represents a more traditional cost-benefit approach. C. Carefully analyzing the costs and benefits associated with each problem and designating the one with the larger costs as the more urgent issue This represents a more traditional cost-benefit approach. D. Taking an iterative approach to solving both problems that involves implementing an adaptive policy that can later be revised based on new information This choice relates to the decision-making processes discussed earlier in the passage and not the cost-benefit discussion from the final paragraph.

A.Examining each issue separately and arriving at a policy decision appropriate for each issue The critics in the final paragraph are in favor of "disaggregating" the problem - that is, pulling apart the various issues and addressing them separately, rather than doing a single, large cost-benefit approach to all of global warming's economic impacts. This is most closely matched by examining each issue separately.

Question 30 The two steps of the Vitamin D synthesis are summarized below. Step 1: 7-dehydrocholesterol + UV light ⇒ previtamin D3 ΔG = -134 kJ/mol Step 2: previtamin D3 ⇒ cholecalciferol (Vitamin D) ΔG = +58 kJ/mol What is the ΔG for Vitamin D synthesis? A. -192 kJ/mol This error results from subtracting 58 kJ/mol from -134 kJ/mol. B. -76 kJ/mol C. +76 kJ/mol This is the value of the reverse reaction. D. +192 kJ/mol This error results from adding 134 kJ/mol to 58 kJ/mol.

B. -76 kJ/mol The overall Gibbs free energy change of the overall reaction (Vitamin D synthesis) is the sum of the ΔG values of both steps. ΔG = (-134 kJ/mol) + (58 kJ/mol) = -76 kJ/mol.

Question 6 What is the mechanical work done by the initial load placed on a fiber if the fiber is linearly deformed by 3 nm? A. 0 J Mechanical work can be calculated using work = Fdcos θ, where F is the force applied, d is the distance over which the force is applied, and θ is the angle between the force applied and the direction of the object's movement. The mechanical work would be zero if the force applied was zero, the distance over which the force was applied was zero, or the angle between the force applied and direction of the object's movement was 90 degrees. None of these are true in this case. B. 3 x 10-8 J C. 3 x 10-6 J This answer could result from miscalculation. D. 1.5 x 10-5 J This answer could result from miscalculation.

B. 3 x 10-8 J Mechanical work can be calculated using work = Fdcos θ, where F is the force applied, d is the distance over which the force is applied, and θ is the angle between the force applied and the direction of the object's movement. Here, we have linear deformation, so θ = 0º. Paragraph 5 states the initial load as 10 N, and the question gives the distance as 3 nm. Work = 10 N (3 x 10-9 m)(cos 0) = 10 (3 x 10-9)(1) = 3 x 10-8 J

Question 10 The data in the passage suggest that which time period during encystation is the level of protein dropping most quickly? A. 0-2 hpie 0-2 shows predominantly up-regulatory behavior. B. 4-6 hpie C. 10-12 hpie The 10-12 hpie interval shows a mix of up-regulatory and down-regulatory behavior. D. 12-14 hpie The 12-14 hpie interval shows a mix of up-regulatory and down-regulatory behavior.

B. 4-6 hpie Figure 1 shows the up- or down-regulation of cwp genes over two-hour intervals. The 4-6 hpie time period shows the largest down-regulation of 15%, as evidenced by the gray bar on the lower half of the plot.

Question 27 What alteration to an HCN channel will reduce the transport of K+ in favor of Na+ transport? A. Increasing the diameter of the channel by adding amino acids B. Decreasing the diameter of the channel by removing amino acids C. Replacing the serine groups in the channel with alanine Changing between serine (polar) and alanine (nonpolar) residues will not favor Na+ over K+. D. Replacing the alanine groups in the channel with serine Changing between serine (polar) and alanine (nonpolar) residues will not favor Na+ over K+.

B. Decreasing the diameter of the channel by removing amino acids Paragraph 1 states that HCN channels are permeable to K+ and Na+ ions. Since Na+ is chemically similar to K+, one can assume the difference must be due to the size of the atom. The K+ ion is larger than the Na+ ion, so reducing the diameter of the channel can allow Na+ to enter while preventing K+ entry.

Question 5 Given the findings in the passage, which additional result most strongly indicates that the TGFBR1 and TGFBR2 receptors regulate TGFβ-dependent epithelial proliferation? A. Treatment with TGFBR1 receptor agonist resulted in reduced MIB1 detection. A decrease in MIB1 levels after treatment with a TGFBR1 agonist is contradictory to the findings of the passage. B. Expression of TGFBR1 and TGFBR2 was observed to increase during intervals of heightened epithelial cell proliferation. C. Genes for several different receptor subtypes were found in untreated epithelium. The fact that genes encoding several different receptor types may be found in epithelial cells does not necessarily imply that TGFBR1 and TGFBR2, specifically, affect epithelial cell proliferation. D. Treatment with new TGFBR3 receptor antagonists decreased the number of MIB1-positive cells. This would show a relationship between TGFBR3 receptors and epithelial growth, but it does not point to TGFBR1 or TGFBR2 involvement.

B. Expression of TGFBR1 and TGFBR2 was observed to increase during intervals of heightened epithelial cell proliferation. Experiment 1 of the passage shows that treatment with TGFBR1 and TGFBR2 antagonists led to lower levels of epithelial cell production. In order to strengthen this conclusion, we want to show a positive correlation between TGFBR activity and epithelial proliferation.

Question 7 The functions of the ESVs of Giardia most closely resemble what cell organelle? A. Lysosomes Lysosomes function as the digestive system of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself. B. Golgi apparatus. C. Nucleolus The nucleolus is the site of cellular rRNA transcription and processing; it also serves as the location of ribosome assembly. D. Centriole The centriole, which helps organize microtubules, is a cylindrical structure consisting of nine triplets of microtubules in the centrosomes of most animal cells.

B. Golgi apparatus Paragraph 2 tells us that encystation specific vesicles (ESVs) give the organism the ability to modify or partition cyst wall cargo during secretory transport. This is most similar to the functions of the Golgi apparatus, which packages and delivers cellular material for transport.

Question 2 The author suggests which of the following about Wittgenstein's early academic pursuits? A. His skill in engineering was notably less significant than his skill in philosophical work. Although the passage tells us that Wittgenstein was obsessed with philosophy, we don't know that he lacked skill in engineering. B. If he had never read the work of Russell and Frege, he likely would have continued working in aeronautics for longer than he did. C. His father's strict, authoritarian approach to child-rearing created the sense of self-discipline that Wittgenstein needed to develop his philosophy. The passage mentions his father's strict style, but doesn't tell us how that style influenced Wittgenstein's philosophical work. D. Wittgenstein's personal fortitude in enduring a POW camp altered his philosophy in a way that gave it a more mystical, religious quality. Religious and mystical qualities are mentioned nowhere in the passage.

B. If he had never read the work of Russell and Frege, he likely would have continued working in aeronautics for longer than he did. The passage presents a direct cause-and-effect relationship by saying that Wittgenstein's obsession with logic, philosophy, and mathematics was sparked by the discovery of philosophical works by Russell and Frege. Absent that spark, it is a reasonable inference that Wittgenstein would have continued his work in aeronautics until something came along later to shift his interests.

Question 17 Which functional group is NOT found on penicillin? A. Amide See the correct answer explanation for where this group is found on penicillin. B. Imine C. Carboxylic acid See the correct answer explanation for where this group is found on penicillin. D. Thioether See the correct answer explanation for where this group is found on penicillin.

B. Imine An amide is a carbonyl group bonded to nitrogen, a carboxylic acid is a carbonyl bonded to an OH, and a thioether group contains a sulfur atom single-bonded to two carbon atoms (C-S-C). Thus, A, C, and D are all found in penicillin, while an imine, a carbon double bonded to a nitrogen atom, is not.

Question 24 In which of the following cell processes does thymidine kinase most likely play a role? A. Osmosis Osmosis refers to the movement of particles, usually water, across a membrane. This process is not associated with thymidine kinase. B. Mitosis C. Translation "Thymidine" resembles the word "thymine," a base typically only present in DNA. Translation does not directly involve DNA; instead, it is the production of protein from an mRNA template. D. Conjugation Conjugation is the transfer of genetic material (plasmids) between bacterial cells by direct cell-to-cell contact or via a bridge-like connection between two cells. This process does not relate to thymidine kinase.

B. Mitosis The passage states that thymidine kinase is used to predict cancer activity. Cancer is a disease categorized by rapid, unregulated cell growth and replication. The name "thymidine" (a nucleotide base) also indicates that the enzyme has a key role in DNA synthesis and therefore in cell division. You should also know that the "kinase" part of the name indicates that the enzyme catalyzes the addition of a phosphate group to its substrate.

Question 23 For which of the following statements does the passage provide the least explanation or support? A. A patient with type 2 diabetes who is trying to quit smoking may be able to improve both of these health factors with regular exercise. This is stated at the start of the passage. B. Patients who discuss exercise plans with their physician are unable to stick with the plan due to how infrequently they are able to get check-ups with their doctor. C. Even studies that include a very large amount of data may nonetheless lead to questionable conclusions. The author tells us about a study in paragraph 4 that included tons of data (thousands of recorded doctor-patient interactions) but still had methodological flaws that made some question its conclusions. D. Patients' own behavior can influence the likelihood that their doctor will discuss exercise plans with them. The passage discusses a study that assess how frequently patients initiate conversations about exercise with their doctors.

B. Patients who discuss exercise plans with their physician are unable to stick with the plan due to how infrequently they are able to get check-ups with their doctor. The very end of the passage tells us that even when patients do discuss exercise regimens with their doctor, they don't seem to be able to start or stick with the plans. However, the passage doesn't tell us (or even suggest) why this is the case.

Question 8 Which of the following incidents may have led to the rift between groups within the IRP? A. A local scandal involving officials of the IRP The impact of scandals and personal history of party members is not discussed as a factor in party allegiance (paragraph 5) or in the context of the rift (paragraph 4). B. Political pressure from national labor unions C. Opinions of the defectors' family members The passage does not support the idea that family opinions would be able to sway a party member's allegiance one way or the other. D. A particularly persuasive campaign speech by a technocrat member Paragraph 5 mentions the charisma of a particular candidate as a reason for disloyalty, but the rift resulted in a defection of a populist faction from the larger technocrat majority. A persuasive speech would, on the contrary, motivate people to stay loyal to the party.

B. Political pressure from national labor unions This question asks us to infer what may have contributed to the rift and eventual schism within the IRP. This situation is described in paragraph 4 as "...an internal rift (that) emerged between the populist and the more technocratic wings of the ruling party over the market reforms and the authoritarian nature of the IRP-dominated political system." In summary, the groups differed over the stern, authoritarian IRP governance. It is implied that recent reforms were more restrictive, unilateral, representing the limited interests of the technocratic wing of the IRP. Note also that this technocratic wing stands in opposition to the populists. A populist movement typically seeks to represent the interests of ordinary people (the populace), so pressure from labor unions could certainly have led this wing of the party to splinter off.

Question 11 Which of the following explains why the pitch of person's resonant voice harmonics rises when they inhale helium instead of air? A. The wavelength increases due to the change in temperature from the helium atoms. There is no reason to think inhaling helium will change the temperature of the air in the larynx. Also, an increase in wavelength would not correspond to an increase in perceived frequency. B. The change in timbre results in a higher perceived frequency of the voice. The pitch of a perceived sound is dependent on its frequency. In the case of the human voice, there are many overlapping waves with various frequencies and higher harmonics of those frequencies. Nonetheless, the basic fact remains that pitch depends on perceived frequency. Thus, when helium atoms are inhaled, the density of the air is being changed, which alters the timbre (an overall quality of voice that results from overlapping waves) to emphasize the higher-pitched harmonics. We perceive that as a high-pitched, "squeaky" voice. However, note that even without knowing the definition of timbre, this question can be solved by eliminating the other options. C. The frequency decreases due to the change in air density from helium atoms. A decrease in frequency would result in a lower-pitched, deeper voice, not a high-pitched squeaky voice. D. The speed of the sound wave remains constant regardless of changes to the medium through which the sound wave propagates. This is false. The speed of sound depends on the bulk modulus, density and temperature of the medium through which it travels (at constant T: vsolid > vliquid > vgas).

B. The change in timbre results in a higher perceived frequency of the voice. The pitch of a perceived sound is dependent on its frequency. In the case of the human voice, there are many overlapping waves with various frequencies and higher harmonics of those frequencies. Nonetheless, the basic fact remains that pitch depends on perceived frequency. Thus, when helium atoms are inhaled, the density of the air is being changed, which alters the timbre (an overall quality of voice that results from overlapping waves) to emphasize the higher-pitched harmonics. We perceive that as a high-pitched, "squeaky" voice. However, note that even without knowing the definition of timbre, this question can be solved by eliminating the other options.

Question 10 Which of the following best explains why, at a constant voltage, warmer solutions are ejected more quickly than cooler ones? A. The droplets have smaller volume at higher temperatures. At higher temperatures, the droplets should have a larger volume, not smaller. B. The surface tension is lower for solutions at higher temperatures. C. The electrical forces grow smaller as temperature increases. Electrical forces, which are generated by the voltage source and by the intrinsic electrical properties of the material, will be unaffected by increased temperature. D. The electrical forces grow larger as temperature increases. Electrical forces, which are generated by the voltage source and by the intrinsic electrical properties of the material, will be unaffected by increased temperature.

B. The surface tension is lower for solutions at higher temperatures. Paragraph 1 states that "electrospinning occurs when the electrical forces at the surface of a polymer solution overcome the surface tension and causes an electrically charged jet to be ejected." If warmer solutions are being ejected sooner, this equilibrium imbalance must be reached sooner. This imbalance can be caused by either an increase in electrical forces or a decrease in surface tension. Electrical forces, which are generated by the voltage source and by the intrinsic electrical properties of the material, will be unaffected by increased temperature. Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. Surface tension decreases as temperature rises, such that as the average kinetic energy of the fluid molecules increases, they are more likely to be able to break the intermolecular bonds holding the molecules together at the surface. Surface tension also decreases as the surface area of the fluid rises due to the molecules being stretched further apart, resulting in a thinner film of surface tension.

Question 17 Suppose archaeologists discover a previously unknown text that discusses Taoist themes and advocates for the practice of Taoist rituals. The author would be least likely to believe which of the following about this text? A. Such a text would have been incorporated into the Tao Tsang if the compilers had known of it. This is likely to be true, since the Tao Tsang was an attempt to compile all available writings. B. The text may have been written at about the same time as the I Ching. C. Any discussion of cosmology included in the new text may have significant overlap with important themes of the I Ching and Yinyangism. The passage tells us that the cosmology of Taoism is mixed up with that of the I Ching and Yinyangism. Significant overlap between these philosophies is thus very possible. D. It may have been considered an important religious text in its own right if it were an influential commentary on the Tao Te Ching. The passage tells us that influential commentaries on the Tao Te Ching were able to develop into important religious texts themselves, so it's entirely feasible that this could have happened with this text.

B. The text may have been written at about the same time as the I Ching. In the fourth paragraph, the passage tells us that "unlike the Zhuangzi, or any other Taoist text, the I Ching predates the Tao Te Ching." In other words, the I Ching is extremely old, much older than any other work discussed. If a new text were discovered, the author would logically find it unlikely that this new text would have an origin as old as the I Ching (thus predating the Tao Te Ching). This is made even more unlikely by the fact that, in the question stem, this new text is described as "discussing Taoist themes." It is unrealistic to think that these themes would be discussed hundreds of years before the central Taoist work was created.

Question 5 Which of the following, if true, would most weaken one of the passage's assertions about Wittgenstein's life? A. Wittgenstein's fluency in English was an absolute requirement for his gaining British citizenship. The passage never discusses Wittgenstein's language abilities, so the English-fluency requirement of British citizenship is irrelevant. B. Wittgenstein halted his philosophical work during WWII in order to act as a nurse for wounded British soldiers, and this interruption prevented him from seriously resuming teaching ever again. C. Near the turn of the 21st century, historians discovered a series of personal letters exchanged between Wittgenstein and Pinsent that confirmed that the two were in a romantic relationship. This would confirm an assertion made in the passage. D. Wittgenstein never received any payment, formal or otherwise, for the initial version of the Tractatus that was published throughout the UK and Austria. This would strengthen an assertion made in the passage.

B. Wittgenstein halted his philosophical work during WWII in order to act as a nurse for wounded British soldiers, and this interruption prevented him from seriously resuming teaching ever again. The passage asserts that World War II did not disrupt Wittgenstein's work, but this choice tells us that, on the contrary, Wittgenstein stopped his academic work to serve as a nurse. Thus, this choice directly weakens one of the passage's assertions.

Question 6 According to the passage, one problem that likely precipitated the 1980s crisis was: A. investors' reactions to disappointing financial information. Investor reactions and fears may have led to the worsening of the crisis, but there is no mention of them in the passage as a leading event. B. a shortage of available government funding. C. a collapse of the state's role in economics. While the passage mentions the relationship between the government and businesses was weakened and that funding was "scaled back," this does not suggest a collapse of the government's role in state economics. D. the first major defection from the IRP. The defection of the IRP is mentioned as occurring in 1988 as a result of, not the cause of, the financial crisis.

B. a shortage of available government funding. This question asks you to identify an event mentioned in the passage as a cause or factor in the financial crisis of the 1980s. Paragraph 4 informs you that in the 1980s, the pattern of Mexican politics began to break down. As public funding dried up, the state's relationships were weakened. This strongly implies that a shortage of available government support is the most likely event to have precipitated the ensuing crisis.

Question 15 According to the passage, Professor Morgan's approach: A. does not provide policies that solve problems. Morgan's approach implements an adaptive policy earlier in the process, but we have no reason to suggest that such a policy cannot solve the problem that it is aimed at. B. feeds back on itself in a way that is different from traditional models. C. takes longer to implement given the multiple rounds of assessment and reassessment. he length of time it takes to use either decision-making framework is not discussed. D. is favored by those who see traditional cost-benefit analysis as inappropriate. The discussion about cost-benefit analysis appears at the end of the passage and is not related to the decision-making approaches discussed.

B. feeds back on itself in a way that is different from traditional models. Paragraph three describes Professor Morgan's approach as an iterative approach that feeds back on itself, with the end stage being further refinement of the problem and improvements to any adaptive policy already in place.

Question 12 The passage suggests that the author believes each of the following EXCEPT: A. no other issue facing decision-makers presents a series of problems in the way that climate change does. The beginning of the passage describes climate change as unique. This means nothing else presents quite the same problems. B. large issues filled with uncertainty cause researchers and policy-makers to develop new approaches that are firmly grounded in the traditional assumptions underlying economic analysis. C. Professor Morgan's approach to problem-solving provides a recursive approach that provides for practical solutions that may not be perfect but allow policy-makers to quickly address the immediate situation. The passage describes Morgan's approach as "iterative" and a "heuristic," which closely matches the language in this answer choice. D. at least some uniquely difficult problems should be expected to lead people to question assumptions and frameworks that they may not have previously. The author thinks it unsurprising that climate change has led some to challenge basic assumptions, so when this choice says "at least some," this is true, since climate change is one such "uniquely difficult problem."

B. large issues filled with uncertainty cause researchers and policy-makers to develop new approaches that are firmly grounded in the traditional assumptions underlying economic analysis. The final paragraph says that it is unsurprising that critics are challenging traditional assumptions like cost-benefit analysis. Thus, saying the new approaches are "firmly grounded in the traditional assumptions" would be incorrect based on the passage, making this the right answer to this "EXCEPT" question.

Question 18 Chitin's flexibility and strength make it favorable as a biodegradable surgical thread. All of the following describe the portion of a chitin molecule shown below EXCEPT: A. carbohydrate. Chitin (C8H13O5N)n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose. This classifies the structure as a carbohydrate. B. polypeptide. C. disaccharide. The two monosaccharide units joined together by a glycosidic bond make this a disaccharide. D. polymer. Monomers joined together make this a polymer.

B. polypeptide. Chitin (C8H13O5N)n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose. The molecule shown comprises two of these rings attached via a β-1,4 linkage. As such, it can be classified as a carbohydrate, a polymer, and a disaccharide. It does not contain amino acid monomers joined via amide bonds, so it cannot be classified as a polypeptide.

Question 5 (p/b) When in vivo studies were performed on the three drug-polymer combinations, it was found patients in the polaxemer-188 group experienced the most stomach pains after administration. Given the results of the study, this is most likely due to: A. elevated drug concentration causing inflammation of the gastric mucosa. The data shows that the glipizide/polaxemer matrix demonstrated the lowest percent of drug release, eliminating this choice, which implies the opposite (that elevated drug concentration is the cause of the pain). If this were the case, the β-cyclodextrin in trial 2 would promote the most pain, since it dissolves the most rapidly. B. tablet fragments causing inflammation of the gastric mucosa. C. glipizide/polaxemer-188 matrices being the smallest of the 3 tested. The passage states that small matrices lead to increased drug release, but the figure indicates that the polaxemer tablets released the drug the most slowly, implying that the polaxemer tablets have large matrices. D. increased pH of the stomach contents. We have no reason to conclude that any of the drug contents alter stomach pH. In fact, basicity (or increased pH) was never mentioned in the passage.

B. tablet fragments causing inflammation of the gastric mucosa. Since the glipizide/polaxemer-188 pill displayed the lowest solubility, the pill must remain partially undissolved for a longer time than the other medications, and the resulting solids could cause the most inflammation.

Question 4 (p/b) The flow rate of stomach content emptying is 100 cm3/sec. Patients who undergo gastric bypass surgery will increase this rate to almost 1600 cm3/sec. Assuming the flow of stomach contents approximates Poiseuille's Law, what change to their gastrointestinal connection would explain this, provided no other changes occur in the conditions of stomach content flow? A. The new connection is 2 times longer. This change would decrease, rather than increase, the flow rate. B. The new connection is 4 times longer. This change would decrease, rather than increase, the flow rate. C. The new connection radius is 2 times larger. D. The new connection radius is 4 times larger. This would cause the flow to increase by a factor of 44 to 25,600 cm3/sec.

C. The new connection radius is 2 times larger. If we model this GI connection as a pipe, we can quantify the flow using Poiseuille's Law, which states: Flow = ΔPπr4 / 8Lη ΔP is the pressure difference across the pipe, r is the radius of the pipe, L is the length of the pipe, and η is the viscosity of the fluid in the pipe. The question states that the flow increased from 100 to 1600 cm3/sec, a 16-fold change. Of all the answers provided, only doubling the radius would result in a 24 increase in the flow.

Question 1 (oral drug passage) (p/b) Which of the following correctly lists the floating lag times for the three trials in increasing order? (note: assume that the mixing of the drug and polymer does not change the density of either component) A. Trial 1 < Trial 2 < Trial 3 B. Trial 2 < Trial 1 < Trial 3 C. Trial 3 < Trial 2 < Trial 1 D. Trial 2 < Trial 3 < Trial 1

C. Trial 3 < Trial 2 < Trial 1 The passage defines lag time as the time taken for the tablet to rise to the surface of the dissolution media. Object flotation is determined only by density - a less dense object will rise quickly in a fluid and will then float with more of its volume above the fluid surface. A more dense object will rise more slowly and will float with more of its volume submerged. (An even more dense object may sink.) At this point, you may guess that the pill with the least dense polymer (trial 3) will rise the most rapidly, giving it the smallest lag time. That would lead you to choice C and you could move on. However, if you wish to do the calculations for density, they are listed below. Note that we are told that all pills have the same volume, so to determine the density of a particular pill, we must simply find the weighted average of the density of its components: Trial 1 is a 1:1 ratio of glipizide (ρ = 0.2) and gelucire (ρ = 0.6), so the density of the pill is: (1/2)(0.2) + (1/2)(0.6) = 0.4 Trial 2 is a 1:4 ratio of glipizide (ρ = 0.2) and β-cyclodextrin (ρ = 0.3), so the density of the pill is: (1/5)(0.2) + (4/5)(0.3) = 0.28 Trial 3 is a 1:8 ratio of glipizide (ρ = 0.2) and polaxemer-188 (ρ = 0.1), so the density of the pill is: (1/9)(0.2) + (8/9)(0.1) = 0.11

Question 22 Some proteins and antibodies are susceptible to pH damage. In order to prevent this damage, what would be the most efficient and effective additional step to perform at the end of the elution process? A. 0.1 M glycine•HCl, pH 3.0 Note that the question asks for an additional step to perform after the elution process has taken place. Acid was already added to elute the proteins from the beads, so this solution would only continue to lower the pH, potentially damaging the molecules. B. 0.1 M NaCl, pH 7.0 This solution has a neutral pH and will not be able to neutralize the acidity of the final eluate. C. 1 M Tris•HCl, pH 8.5 D. 0.7 M KOH, pH 13.85 This solution is far too strong; a very high pH can damage the molecules as much as an excessively low pH.

C. 1 M Tris•HCl, pH 8.5 The passage describes the final step of the process as lowering the pH to elute the proteins off of the beads. To reduce the risk of damage, we need to neutralize any excess acid. 1 M Tris•HCl, pH 8.5 is the buffer that will most effectively dissociate most protein:protein and antibody:antigen binding interactions without permanently affecting protein structure. Eluted protein fractions are best neutralized immediately by addition of alkaline buffers.

Question 11 Which of the following would most closely parallel the traditional decision-making process it is described in the passage? A. A non-profit organization examines the costs for a number of different initiatives and chooses the one whose potential benefit maximizes the utility of dollars spent. This relates to cost-benefit analysis as described in the final paragraph rather than the decision-making described in the second paragraph. B. An oil refinery's manager allocates several portions of the plant's equipment and space to simultaneously test several potential improvements on refining techniques while continuing to implement traditional ones. This is closer to Morgan's recursive approach, where an adaptive policy is started at the same time as work is continued on the problem. C. A beverage company does several consumer surveys and focus groups and uses the results to design and then sell a new brand of soda. D. An education company goes out of business because it chooses not to invest in new learning technologies while its competitors all do so. The notion of getting out-competed is not relevant to the passage.

C. A beverage company does several consumer surveys and focus groups and uses the results to design and then sell a new brand of soda. Traditional decision-making is a linear process in which research leads to options, which lead to implementation and a solution to the issue. This matches the idea of doing surveys first and then designing a new product based on those surveys.

Question 15 Early research into the mechanism of antibiotics theorized that it was implausible that the amide in penicillin would convert to an ester. Which of the following explains this doubt? A. Amides possess better leaving groups than esters. This statement is false. Additionally, note that if choice A were true, choice B would necessarily be true as well, which is an impossibility. B. Esters possess poorer leaving groups than amides. This statement is false. Additionally, note that if choice A were true, choice B would necessarily be true as well, which is an impossibility. C. Amides are less reactive than esters. D. Serine contains no good nucleophiles. Serine contains an -OH group on its side chain. The oxygen atom of this group is electron-rich and able to act as a good nucleophile.

C. Amides are less reactive than esters. Carbonyl reactivity is determined by the strength of the leaving group attached to the carbonyl. Good leaving groups are usually weak bases. For the MCAT, you can simply remember the relative reactivities of these carboxylic acid derivatives, starting with the most reactive: acyl halides > anhydrides > esters and acids > amides. It is not thermodynamically favorable for a molecule to transform from a less reactive (more stable) form, like an amide, to a more reactive (less stable) form, like an ester.

Question 26 In patients with a certain medical condition, the intercellular path described in the passage is damaged in the large intestine, causing lower levels of transport. What change would be expected? A. Increased Cl- in the lumen of the colon Lower levels of transport will result in lowered Cl- levels in the lumen of the colon. B. Decreased Cl- in the lumen of the duodenum The question stem referenced only the large intestine. The duodenum is the region of the small intestine that is most proximal to the stomach. C. Decreased waste fluidity in the colon D. Increased waste fluidity in the colon This would be caused by increased, not decreased, chloride ion transport.

C. Decreased waste fluidity in the colon Paragraph 3 states that this pathway can be used to transport ions and fluids into the lumen of the large intestine. The addition of fluid softens the waste material and allows it to move. Without this mechanism, fewer ions will be secreted into the lumen and less water will follow. This will results in a dehydrated, more solid waste in the colon.

Question 13 Which of the following would the passage author most likely recommend to a multi-national corporation seeking to utilize portfolio theory to deal with uncertainty? A. Mitigate risk by placing financial resources in very different sectors of the economy within the most politically stable nation available Portfolio theory specifically suggests working across different countries, not within a single one. B. Take a recursive approach to decision-making that allows risk reduction by updating strategies in the face of new information This is a decision-making approach from the third paragraph, not the portfolio theory from the fourth paragraph. C. Diversify business holdings across different sectors in different countries' economies D. Avoid investing in either petrochemical industries or those businesses that rely on biodiversity in subtropical climates The mention of petrochemical industries and subtropical climates is a side example used near the end of the passage and is not relevant to portfolio theory.

C. Diversify business holdings across different sectors in different countries' economies Portfolio theory is discussed in the fourth paragraph as a way to reduce risk by spreading out investments as broadly as possible. Diversifying holdings across different sectors in different countries would most align with this.

Question 1 In the first paragraph, the passage implies which of the following about Wittgenstein's work? A. Despite claiming to be his disciples, many of Wittgenstein's followers intentionally misrepresented his ideas. The passage never suggests that anyone was being malicious and intentionally skewing Wittgenstein's ideas. B. Wittgenstein would not have approved of the final, edited form of the Philosophical Investigations and would have insisted on significant rewrites. Since the work was compiled after he died, we have no particular way of knowing what Wittgenstein would have thought of the Philosophical Investigations. His choice not to publish those manuscripts while alive may suggest he thought they were not yet ready to be published, but nothing in the passage tells us what he would have thought of the editing job done after his death. C. Had Wittgenstein published more works during his life, his ideas may have been better understood by others. D. Wittgenstein's small publishing output was a result of his being distracted by his engineering interests, in particular aeronautical engineering. Wittgenstein's engineering work came earlier in his life than his later philosophical work, so there couldn't be any distractions there.

C. Had Wittgenstein published more works during his life, his ideas may have been better understood by others. In the first paragraph, the passage tells us that the misunderstanding that people have of Wittgenstein's work is partly his fault and then immediately follows by stating how little he published while alive. This implies that, had he published more work, he may have been better able to explain himself and be better understood by others.

Question 20 According to the passage, which of the following can be inferred regarding Taoist religious texts? I. The Tao Te Ching lacks the historicity of the Qur'an. II. The authorship and structure of the Zhuangzi, unlike the Tao Te Ching, has been clearly established by historians. III. The Tao Tsang lacks the coherence of the Talmud. A. I only B. II only This is probably false, since the passage tells us that the origin of the Zhuangzi is both ancient and shrouded in mystery. The third paragraph specifically mentions that the work was "supposedly" written by Zhuangzi and his disciples, giving us a tenuous authorship, at best (II). C. I and III only D.I, II, and III The passage tells us that the origin of the Zhuangzi is both ancient and shrouded in mystery. The third paragraph specifically mentions that the work was "supposedly" written by Zhuangzi and his disciples, giving us a tenuous authorship, at best (II).

C. I and III only At the start of the passage, the author concedes that Taoist religious texts lack two major qualities found in other works: coherence and historicity. The author specifically cites the Qur'an and the Talmud as works that have these qualities. Therefore, the Taoist texts would lack these qualities when compared to Western religious texts (I and III).

Question 10 Which of the following words would the author most likely use to describe the establishment of the IRP as the "official" party? A. Short-sighted Given that the IRP lasted for decades, their methods could not be described as "short-sighted." B. Immoral There is no discussion of morals by the author of this passage when it comes to the IRP party or its role in economic dominance. C. Manipulative D. Generous While the IRP did provide funds, it is implied that such funds were only given in exchange for party support. This would not be characterized as generous.

C. Manipulative Phrases used in paragraph 2 include "...dispense state funds to organizations supportive of the 'official' party..." and "...newly created interest groups depended heavily on the state for their financing and were required to maintain strong ties to the ruling party." This implies that the IRP used economic influence to control and coerce businesses to support the party. When the funds dried up later, "the pattern of Mexican politics instituted by Calles and Cárdenas began to break down." This all serves to suggest that these connections were made out of self-preservation, or manipulation, rather than though a genuine feeling of support.

Question 7 Which of the following waves would have a wavelength larger than any standard electrospun fiber? A. Red light This would not be the longest wavelength of these choices. B.Blue light This would not be the longest wavelength of these choices. C. Microwaves D. X-rays This would not be the longest wavelength of these choices.

C. Microwaves Since only one of these options can be correct, we are simply looking for the choice with the largest wavelength. Be familiar with the electromagnetic spectrum! Visible light (ROYGBIV) ranges from approximately 7 x 10-7 m to 4 x 10-7 m in wavelength. X-rays are smaller than all visible light, with wavelengths around 1 x 10-11 m. Finally, microwaves are larger than visible light waves, with wavelengths of 1 x 10-3 m. As the longest-wavelength option, microwaves must be the correct answer.

Question 18 On the penicillin heteroatom ring, what is the absolute configuration of the carbon labeled 1? A. + This answer refers to optical activity, which can only be determined experimentally. B. - This answer refers to optical activity, which can only be determined experimentally. C. S D. R This is the reversal of the correct answer (S configuration). If you chose this answer, you may have incorrectly identified the priorities of groups attached to the carbon.

C. S The carbon labeled 1 is sp3 hybridized, indicating that its geometry is tetrahedral. This allows us to infer that the unwritten H atom attached to C1 is coming out at us, above the ring. Using the method of chiral designation: 1) Identify the four substituents bonded to the carbon in question. 2) Assign priorities to those substituents (atomic number ~ priority). 3) Count 1-2-3 and record what direction you move in. Counterclockwise = S, clockwise = R (remember the mnemonic "clockwise is the Right way for a clock to run"). 4) Determine which direction the lowest-priority (#4) group is facing. If #4 faces away from you, keep your answer. If #4 is coming out at you, invert your designation. Dashed wedges indicate that the atom is facing away from you, while solid wedges indicate that the atom is coming out at you. Here, #1 priority is the nitrogen atom, while #2 priority is the carbon bonded to sulfur and #3 priority is the carbon bonded to oxygen. Looking at this carbon, we are moving clockwise from 1 to 2 to 3, but the #4 group, the unwritten H, must be facing out of the screen; thus, this carbon has the S designation.

Question 12 The figure shown below shows the pressure and volume changes of the left ventricle during the cardiac cycle for two different patients. Which of the following is true? A. The change in systolic pressure in patient 1 is greater. Since pressure is denoted on the y-axis, the changes in diastolic and systolic pressure are represented by the "heights" of the curves during relaxation and contraction. These "heights" appear to be the same for both patients B. The change in diastolic pressure in patient 1 is greater. Since pressure is denoted on the y-axis, the changes in diastolic and systolic pressure are represented by the "heights" of the curves during relaxation and contraction. These "heights" appear to be the same for both patients C. The work done by patient 2's left ventricle is greater. The area under or inside the curve represents the product of the two variables on the axes. For fluid systems, Wby system = PΔV. Here, you can see that patient 2 has a greater change in volume at the same pressures during filling and emptying. Thus, the left ventricle of patient 2 is doing more work. The PΔV curve also encloses a larger area, so if you know that the area inside the curve represents work, you can quickly conclude that patient 2's heart is doing more work. D. The work done by patient 1's left ventricle is greater.

C. The work done by patient 2's left ventricle is greater. The area under or inside the curve represents the product of the two variables on the axes. For fluid systems, Wby system = PΔV. Here, you can see that patient 2 has a greater change in volume at the same pressures during filling and emptying. Thus, the left ventricle of patient 2 is doing more work. The PΔV curve also encloses a larger area, so if you know that the area inside the curve represents work, you can quickly conclude that patient 2's heart is doing more work.

Question 3 After injury-induced cataract formation has begun, which of the following are LEAST likely to be found in nearby monocytes? A. TGFβ transporters The passage states that monocytes export their TGFβ once it is synthesized. The cells must have a mechanism to transport this TGFβ into the aqueous humor. B. TGFβ receptors TGFβ receptors are involved in recognizing TGFβ molecules. According to the passage, monocytes are able to recognize and respond to the presence of TGFβ to aid in the inflammatory response. This means the cells must have functional receptors on their surface. C. Tight junctions D. Cytokines Cytokines are small proteins that are important to cell signaling processes, like inflammation and immune response. Cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations.

C. Tight junctions Tight junctions are areas where the membranes of two closely-joined cells adhere tightly and form a near-impenetrable barrier. This is a hallmark of epithelial barriers and is not likely to be a property of nearby monocytes. In addition, the passage says that the epithelial cells are undergoing a transition into mesenchymal cells (EMT) during this process. Thus, the number of epithelial cells would be decreasing as they turn into mesenchymal cells, which do not have such tight junctions.

Question 17 Patients with excess fat are more likely to require larger therapeutic doses of which vitamin? A. Vitamin B1 Since this vitamin is water-soluble, its absorption is unlikely to be affected by excess fat. B. Vitamin C Since this vitamin is water-soluble, its absorption is unlikely to be affected by excess fat. C. Vitamin D D. Vitamin B3 Since this vitamin is water-soluble, its absorption is unlikely to be affected by excess fat.

C. Vitamin D The lipid-soluble vitamins are A, D, E, and K. The water-soluble vitamins are B and C. Greater amounts of subcutaneous fat sequester more of the lipid-soluble vitamins and lower their release into the circulation. Thus, excess fat increases the initial dose of vitamin required to achieve a particular effect.

Question 13 In the figure below, the black line represents an enzyme-catalyzed reaction and the grey line represents that same reaction after adding 0.05 mM of factor X. Factor X can best be described as: A. a noncompetitive inhibitor. A noncompetitive inhibitor would lower the Vmax but leave the Km unchanged. B. an allosteric activator. An activator would not increase the [substrate] required to reach Vmax, as the image depicts. C. a competitive inhibitor. A competitive inhibitor will increase the Km of a given reaction while leaving the Vmax unchanged at high substrate concentrations. This is depicted in the figure. D. a chelating agent. A chelating agent is typically an organic molecule that forms two or more coordinate bonds with a metal atom or ion. We have no particular reason to suppose that this competitive inhibitor is a chelating agent.

C. a competitive inhibitor. A competitive inhibitor will increase the Km of a given reaction while leaving the Vmax unchanged at high substrate concentrations. This is depicted in the figure.

Question 20 32P has a very short half-life of 14 days and decays into sulfur as shown below. 32/15P --> 32/16S + e- This nuclear reaction is an example of: A. alpha decay. Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (He nucleus), thereby transforming into an atom with a mass number 4 less and an atomic number 2 less than those of the parent species. B. beta plus decay. In β+ decay, or positron emission, the parent nucleus converts a proton into a neutron while emitting a positron (e+). C. beta minus decay. D. positron emission. In β+ decay, or positron emission, the parent nucleus converts a proton into a neutron while emitting a positron (e+).

C. beta minus decay. In β- decay, the weak parent nucleus converts a neutron into a proton while emitting an electron (e-). The atomic mass stays constant while the atomic number increases by 1.

Question 18 The author asserts that the major difference between the Tao Te Ching and the Zhuangzi is that: A. the Zhuangzi attempts to show how to apply Taoist concepts in daily life by using short, abstract poems. This is a distortion; it is the Tao Te Ching that uses short abstract poems . B. the Tao Te Ching developed after the Zhuangzi as a distillation of the core concepts of Tao and Te expressed in the Zhuangzi. This is the opposite of what the passage asserts. We're told that the Tao Te Ching has been a subject of debate for "two and a half millennia," giving it an authorship date around 400-500 BC. The Zhuangzi was written almost 800 years later, around 400 AD. C. the Zhuangzi attempts to be more practical, both in its subject-matter and in its style. D. the Tao Te Ching requires its readers to have fully contemplated the works of the meditation grotto for full appreciation. The grottoes of the Tao Tsang were not compiled until centuries or millennia after the Tao Te Ching, so it doesn't seem reasonable that fully appreciating the Tao Te Ching could require reading through the works in the Tao Tsang.

C. the Zhuangzi attempts to be more practical, both in its subject-matter and in its style. The third paragraph tells us that the Zhuangzi focuses on practical application and has a more down-to-earth style, which includes parables and dialogue.

Question 3 (p/b) A student prepA student preparing for the experiments inadvertently adds an additional 400 mL of the same acid solution to the dissolution vessel. What will be the new pOH of this solution? A. 1.0 The question asks for pOH, which should be greater than 7 for a solution of concentrated acid, eliminating this answer choice. B. 6.0 The question asks for pOH, which should be greater than 7 for a solution of concentrated acid, eliminating this answer choice. C. 11.0 This answer results from an incorrect assumption or calculation. See the correct answer for a complete explanation. D. 13.0

D. 13.0 First, note that the question asks for pOH, which should be greater than 7 for a solution of concentrated acid. This eliminates choices A and B. To decide between the remaining options, remember that solution chemistry tells us that if concentration remains the same, then volume changes will not affect pH. The pH of a solution is calculated by taking the negative log of the proton concentration. For this experiment, the dissolution vessel contains 0.1 M HCl, whether it is the original 900 mL or the 1300 mL present in this question. For the MCAT, we can assume that a strong acid will completely dissociate, meaning the effective [H+] = 0.1 M = 1 x 10-1 M. Calculating the pH gives -log[1 x 10-1] = 1. We should also remember that at standard conditions, pH + pOH = 14 for any aqueous solution. Thus, we can calculate the pOH = 14 - pH = 14 - 1 = 13.

Question 6 What is the expected ploidy of a cyst that has completed an encystation? A. 2n See answer choice D for a correct explanation. B. 4n See answer choice D for a correct explanation. C. 8n See answer choice D for a correct explanation. D. 16n

D. 16n The protozoa will typically be diploid, and as stated in the second paragraph, cyst formation involves a round of DNA replication, followed by nuclear replication, followed by a second round of DNA replication. This process is illustrated below, and the presence of 4 4n nuclei yields a final total ploidy of 16n.

Question 8 Assuming a mass of 0.04 g, what is the power exerted by the electrical forces on a fragment of fiber if the fragment has a velocity of 200 mm/s, 10 ms after ejection? A. 5 x 10-10 W This is the result of a miscalculation. B. 1 x 10-8 W This is the result of a miscalculation. C. 2 x 10-5 W This is the result of a miscalculation. D. 8 x 10-5 W

D. 8 x 10-5 W Mechanical power is a measurement of work/time (J/s, also known as watts). Via the work-energy theorem, we can calculate: Work = ΔKE = KEf - KEi Thus, power can be calculated as ΔKE/time. Remember also that KE = ½ mv2. Power = [½ (0.04 x 10-3 kg)(200 x 10-3 m/s)2] J / (10 x 10-3) s = (0.5 x 4 x 10-5 x 4 x 10-2) / (1 x 10-2) = 8 x 10-5 J/s

Question 3 Which of the following people would the author find to have had a career most analogous to Wittgenstein's? A. A musician who created one of the most successful rock singles of all time but who otherwise spent his career touring small venues where he covered other musicians' songs The passage never suggests that Wittgenstein spent time working on other writer's works. B. A sculptor whose life's work was a single massive building containing and composed of dozens of distinct sculptures Wittgenstein's one published work, the Tractatus, was a small book, not a massive one. C. A physics professor who is willing to spend several years forgoing the professional acclaim that comes from original research because she knows that it is more important that she create a much-needed textbook to fill a gap in her school's undergraduate curriculum Although Wittgenstein took time to teach schoolchildren, it was because a company refused to publish his Tractatus, not because he willingly took time away from his work to publish a "much-needed" other book. D. A law professor who only published a single, highly influential book analyzing the structure of Supreme Court decisions but whose collected lecture notes were posthumously published as a series of law review articles

D. A law professor who only published a single, highly influential book analyzing the structure of Supreme Court decisions but whose collected lecture notes were posthumously published as a series of law review articles The passage tells us that Wittgenstein only published a single influential work during his life and that the rest of his manuscript work was collated after he died into the Philosophical Investigations. This most resembles the professor who published a single work and then had the rest of his writing published after he died.

Question 28 Which of the following properties explains why sound wave velocity increases as it travels from air to a liquid medium at the same temperature? A. Kinetic energy of the medium Since the gas and liquid are stated to have equal temperatures, their kinetic energies should be equal as well. Remember, Tfluid ~ KEavg. B. Volume of the medium The volume of the medium does not affect sound wave velocity. C. Density of the medium Density has an inverse relationship to sound wave velocity. A density increase (e.g., from warm air to cold air) would cause velocity to decrease. D. Bulk modulus of the medium

D. Bulk modulus of the medium In general, sound travels fastest in solids and slowest in gases. The equation for sound velocity is given by v = √(Κ/ρ), where K is a coefficient of stiffness termed the bulk modulus (or the modulus of bulk elasticity for gases) and ρ is the density. From this equation, we can see that the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material; since solids are considerably more stiff than liquids and especially gases, sound travels fastest through them. Since density is present in the denominator of the equation, sound waves moving through two equally-stiff solids will travel faster in the less dense material. But when comparing solids to gases, density has a smaller effect than stiffness, because the extent to which a typical solid is more stiff than a gas far exceeds the ratio of their densities.

Question 19 Which of the following is most likely to be the precursor of the group found linked to the N-terminus of a Wnt protein? A. (NH2)6COOH NH2 groups would not form a fatty acid chain. B. CH3(CH2)8OCH3 This is an ether group, not a fatty acid. C. C6H6 This is benzene, an aromatic ring, not a fatty acid.

D. CH3(CH2)10COOH Paragraph 1 tells you that "Wnts are unusual as secreted proteins in that they have a fatty acid chain covalently attached to their N-terminus." Fatty acids are long alkyl chains that terminate in a carboxylic acid group.

Question 23 Which step of the procedure corresponds to the release of DNA-coupled conjugates? A. B B. C C. E D. D

D. D We are looking for the step in which the DNA-coupled antibodies are released. Paragraph 2 outlines each step of the procedure shown in Figure 1. Beginning with step A, DNA oligonucleotides are hybridized to the oligonucleotides in the mixture. In step B, agarose beads are used to capture the biotinylated capture oligonucleotides, both in the form of conjugates and free oligonucleotides. In step C, the unconjugated antibodies are removed by washes. In step D, the MlyI enzyme is used to cleave the captured oligonucleotide hybrids, allowing both conjugates and oligonucleotides to be eluted from the solid support. Thus, step D is our answer. At that point, you should answer the question and move on. However, note that in step E, the eluate is then incubated with protein G beads, while free oligonucleotides are removed by washes. Finally, in step F, purified conjugates are eluted from the solid support.

Question 19 Which of the following would most weaken one of the author's central arguments? A. In several major schools of Taoist teaching, the grotto of meditation is taught as the middle grotto in the progression towards becoming a master, with the final grotto being the grotto of rituals. The author only briefly discusses the three grottoes. Even if this choice does weaken that minor point, note that the question directly refers to the author's central arguments. B. The parables presented by the Zhuangzi are held as infallible representations of the Tao in action in daily life, and questioning the core truth of these stories is typically punished by banishment from the community. This would add to the idea that Taoism has sacred texts, that it is not a "religion without religious texts." As such, it does not weaken the passage at all. C. During Taoist ceremonies, the priest's copy of the Tao Te Ching is treated reverently, placed on a special dais between readings, with only the priest being permitted to touch the book. This would add to the idea that Taoism has sacred texts, that it is not a "religion without religious texts." As such, it does not weaken the passage at all. D. Despite the existence of many works that discuss Taoist themes, the texts themselves are not seen as sacred by most Taoists and the ideas expressed in these works are taken as general guidance that can be disregarded by any local priest or follower of the religion.

D. Despite the existence of many works that discuss Taoist themes, the texts themselves are not seen as sacred by most Taoists and the ideas expressed in these works are taken as general guidance that can be disregarded by any local priest or follower of the religion. The author starts by presenting a view he will oppose: that Taoism is a religion without religious texts. He then goes on to discuss Taoism's various religious texts at great length. However, if it were true that these works were not seen as sacred, or if they were perceived as having no particular authority, then that would weaken one of the author's central concerns in the passage.

Question 2 Monocytes, in conjunction with epithelium-derived factors, can act to facilitate which biological process? A. Fatty acid oxidation While oxidized fatty acids have been shown to aid in monocyte activation, monocytes do not facilitate fatty acid oxidation. B. Transfection Transfection is the process of introducing nucleic acids to cells, usually by way of a non-viral vector. C. Lipid synthesis Synthesis of fatty acids takes place in the cytoplasm and involves 1) initiation via the formation of acetoacetyl carrier protein and 2) an elongation cycle where carbon units are successively added to the growing chain. Neither of these processes involve monocytes. D. Host immune response

D. Host immune response Monocytes are the largest type of white blood cells. Factors secreted by the epithelium help form a cascade that leads to accumulation of immune cells at the site of an injury.

Question 25 Which of the following could serve as an appropriate title for the passage? I. Physician-Recommended Exercise Plans: Disparities in Action II. The Benefits of Exercise in Addiction Recovery III. Doctors and Patients Both Fail to Adequately Address Exercise A. I only B. III only C. I and II only The benefits of exercise in addiction recovery are only mentioned briefly in the first paragraph. A good title should sum up the whole passage, or at least the major focus (II). D. I and III only

D. I and III only The passage is concerned with the exercise plans recommended by doctors, the various factors that influence when such discussions take place, and the disparities that exist in which patients get time spent addressing such plans. The author discusses studies that address the behavior of both the patients and the healthcare professionals. Thus, these both adequately sum up the general discussion in the text (I and III).

Question 16 Which of the following will cause a blood pH of 8.2? A. Decreased O2 concentration O2 concentration itself does not directly impact blood pH, but the hypoventilation that could cause decreased O2 concentration would cause blood pH to fall below 7.4. B. Decreased tidal volume This will cause blood pH to drop below 7.4 due to decreased exhalation of CO2. C. Increased H2O concentration Adding more water to the blood would not cause the system to become more basic. D. Increased respiratory rate

D. Increased respiratory rate Physiological pH is 7.4; thus, 8.2 represents an increase in pH, or alkalosis. The bicarbonate buffer system of the blood is given by: H+ (aq) + HCO3- (aq) ↔ H2CO3 (aq) ↔ H2O (l) + CO2 (g) According to Le Châtelier's principle, a decrease in products will cause the equilibrium to shift to the right. An increased respiratory rate will cause excess CO2 (a product) to be exhaled. The resulting rightward shift will cause a drop in H+ concentration and, thus, an increase in pH.

Question 7 Which of the following is NOT characterized as a contributing factor to present-day Mexican politics? A. Adherence to a legal precedent This factor is discussed in paragraph 1 ("adherence to a highly codified civil law tradition..."). B. Uneven power among branches of government This factor is also referenced in paragraph 1, which mentions the "deference accorded the executive over other branches of government." C. Foreign military occupation This factor is discussed in paragraph 6 ("...traumatic experiences of the nineteenth century, including foreign military occupations..."). D. Land grants from the United States

D. Land grants from the United States This question requires you to research several answers to identify the one factor that is not cited by the passage as contributing to the current political climate. This background information can be found throughout the passage, and only the land grants are not mentioned. In fact, the final paragraph states the opposite: that the U.S. took land from Mexico at some point in history.

Question 21 Which nucleophile was likely used to prepare the oligonucleotides used in the purification procedure? A. NaOH This reagent does not include N3-. B. (CH3)3CCl This reagent does not include N3-. C. HCN This reagent does not include N3-. D. NaN3

D. NaN3 Paragraph 2 states that the oligonucleotides are azide-modified. Azide (N3-) is a powerful nucleophile which can readily add to available electrophiles, such as nucleotide molecules.

Question 21 In the study discussed in the fourth paragraph, the researchers created audio recordings of the doctor-patient interactions in order to: A. prove that physicians unconsciously discriminate against lower class patients by not discussing exercise with them. "Prove" is often a sign of an incorrect answer, as it is extremely strong. This choice also extends far beyond the passage, both by saying that the researchers were setting out to "prove" a particular conclusion in advance, and by stating outright that the physicians were discriminating. B. determine differences in doctor-patient interactions when the doctor and patient are of the same or of different ethnicities. This is the opposite of what the passage says, as we're specifically told that the study failed to address this factor. C. ascertain whether doctors were more likely to discuss exercise regimens with obese male patients than with obese female patients. This is the opposite of what the passage says, as we're specifically told that the study failed to address this factor. D. assess both how often exercise was discussed and for how much time it was discussed.

D. assess both how often exercise was discussed and for how much time it was discussed. The passage directly gives us information about both the frequency of exercise-related discussions (22% more for patients from a high economic class) and the duration of such conversations (420% longer conversations).

Question 25 Studies show that macula communicans are common but not found in tissues such as the gall bladder and skeletal muscle. One possible explanation for this could be that these organs are: A. not under autonomic nervous control. The gall bladder is under autonomic control, while skeletal muscle is under somatic control. B. not involved in digestion of materials. The gall bladder is directly involved in secreting bile for digestion, but neither the gall bladder nor skeletal muscle is involved in the absorption of nutrients. C. not involved in secretion of materials. The gall bladder is directly involved in secreting bile for digestion, but neither the gall bladder nor skeletal muscle is involved in the absorption of nutrients. D. not involved in absorption of materials.

D. not involved in absorption of materials. The passage states that gap junctions allow for the exchange of ions and fluids. One such reason for their absence would be that the organs in question have no need for absorptive or secretive mechanisms.

Question 12 The easiest method to separate the two subunits of the botulinum protein for subsequent analytical purposes would be: A. gas chromatography. Gas chromatography separates molecules based on affinity and would thus be less useful than SDS-PAGE, which separates based on size alone. GC also requires that the molecules be vaporized, and typical proteins are much too large to be easily vaporized. B. mass spectrometry. Mass spectrometry is used to measure the size of one molecule and would not be useful to carry out a separation of two molecules. Remember that subjecting a sample to mass spec ionizes the molecule and breaks it into smaller ion fragments. After conducting such a procedure, you would not be left with two samples that could be subjected to further analysis. C. thin-layer chromatography. Thin-layer chromatography separates molecules based on affinity and would not be useful to separate molecules by size. D. size-exclusion chromatography.

D. size-exclusion chromatography. The second paragraph states that the two subunits are different in size (100 kDa vs. 50 kDa). Size-exclusion chromatography could therefore be used to separate the two proteins by size.

Passage 1 (Questions 1 - 5) Cataract generation triggered by lens injury is considered to be driven by the action of the proliferation and epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) as a complication of injury and inflammation. The epithelium quickly expands, creating a hundredfold increase in the number of cells. In response to trauma, irritation or surgery, cytokines and growth factors increase in the aqueous humor and stimulate LECs to proliferate and undergo EMT. This response is significantly diminished in organisms where EMT is inhibited by the inactivation of transforming growth factor β (TGFβ), especially TGFβ2, the major isoform in the aqueous humor. Key terms: cataract generation, EMT, LECs, injury stimulate LECs to proliferate, cytokines, growth factors, diminished where EMT is inhibited, TGFβ2 Cause and effect: injury to the lens causes inflammation, which leads to increased LEC production and EMT; this process is stimulated by cytokines and growth factors and inhibited when TGFβ is inactivated During the process of EMT, LECs undergo cytoskeletal rearrangement, with the addition of a large amount of extracellular matrix proteins, such as collagen and fibronectin. In anterior cataracts, the proliferation and EMT of LECs in situ leads to the formation of opaque plaques just beneath the lens anterior capsule. Key terms: EMT, cytoskeletal rearrangement anterior cataracts, opaque plaques Cause and effect: EMT causes increases in cytoskeletal components, resulting in plaques under the lens that form cataracts The production of TGFβ is catalyzed by histone deacetylase-1 (HDAC1). HDAC1 removes acetyl groups from N-acetyl lysine groups on histone. Once synthesized, TGFβ is secreted by activated monocytes in the aqueous humor. Since monocytes mediate almost 80 percent of the local TGFβ, scientists tested the theory that TGFβ is responsible for the monocytes' impact on LEC production. The number of LECs expressing MIB1, a nuclear protein, was utilized as a measure of LEC proliferation and expected EMT. Key terms: production of TGFβ, HDAC1 catalyst, histone, monocyte secreted TGFβ, test theory that TGFβ is responsible, MIB1, measure LEC proliferation Cause and effect: the histone modifying enzyme HDAC1 catalyzes TGFβ production; TGFβ is then secreted; a test is conducted to determine TGFβ role in monocytes Experiment 1 After simulated injury, monocyte/LEC cultures were treated with an antibody that lyses all but a negligible fraction of available monocytes; a division of these cultures was also treated with a TGFβ agonist. A second set of cell cultures was treated with antagonists of epithelial cell TGFβ receptors TGFBR1 and TGFBR2 (Table 1). Key terms: cultures treated, lysed monocytes, TGFβ agonist, TGFβ receptor antagonists Table 1 Results of the study on monocyte lysis, TGF agonist, and TGF receptor antagonists Table 1 results show that the addition of the antibody significantly lowered MIB1 levels, and when treated with a TGFβ agonist, the MIB1 levels recovered. Receptor antagonist TGFBR1 also significantly reduced MIB1 levels, but the addition of a 2nd antagonist did not reduce levels much further. Experiment 2 In an effort to determine whether MIB1 is associated with LEC regulation, LEC density was assessed during the course of epithelial growth in wild-type and MIB1-null cell cultures (Figure 1). Key terms: MIB1, LEC regulation, LEC density assessed wile-type, MIB1-null Figure 1 Growth of LECs after an injury in both wild-type and MIB1-null strains Figure 1 shows us that the presence of MIB1 serves to increase LEC count

Passage 1 of bio/c with additional information for questions 1-5

Passage 2 (Questions 6 - 10) CARS Mexicans have long attributed the origins of their political system to the Revolution of 1910-20. They cite the constitution of 1917 as the foundation of their modern political institutions and practices. Mexico's governing institutions and political culture also bear the imprint of three centuries of Spanish colonial rule. Mexicans' adherence to a highly codified civil law tradition, their acceptance of heavy state involvement in business and civic affairs, and the deference accorded the executive over other branches of government can be traced to the administrative and legal practices of the colonial period. Key terms: Mexicans, origins of their political system, Revolution Cause and effect: Spanish colonial rule created a system that has a civil law tradition, heavy state involvement, and a strong executive branch During the 1920s, President Elías Calles reorganized Mexican politics along corporatist lines to contain latent social conflicts. Calles expanded government bureaucracy to enable it to mediate among rival constituencies and to dispense state funds to organizations supportive of the "official" party. Calles also created umbrella organizations that lumped together disparate groups according to broad functional categories. Newly created interest groups depended heavily on the state for their financing and were required to maintain strong ties to the ruling party, the newly created Institutional Revolutionary Party (IRP). Key terms: 1920s, Calles, IRP Cause and effect: Calles reorganized the government, expanded bureaucracy, and used money to buy the loyalty of many groups Calles's successor, Lázaro Cárdenas, revived populism as a force within the IRP by redistributing land to landless peasants via state-sponsored communal farming known as the ejido system. Cárdenas emphasized nationalism as a political force by expropriating the holdings of foreign oil corporations. By 1942, the political processes and institutions that would define Mexican politics for the next forty years were established: a strong federal government dominated by a civilian president and his loyalists within the ruling party, a symbiotic relationship between the state and the official party, a regular rotation of power among rival factions within a de facto single-party system, and a highly structured corporatist relationship between the state and government-sponsored businesses. Key terms: Cardenas, populism, ejido Cause and effect: the government expanded power by seizing oil company holdings and giving land to peasants to create populist loyalty During the 1980s, the pattern of Mexican politics instituted by Calles and Cárdenas began to break down. Public funding for a variety of programs dried up, which led to the state's role in the economy being scaled back, and the relationships developed over four decades between government agencies and legally recognized constituent groups were weakened. An internal rift emerged between the populists and the more technocratic wing of the ruling party over the market reforms and the authoritarian nature of the IRP-dominated political system. This internal rift developed into the first major mass defection from the IRP when a key minority group broke ranks and contested the 1988 presidential election as a coalition of populist parties. Key terms: 1980's, technocratic wing Contrast: IRP had a sharp division between the populists (the peasants) and the technocratic wing (passage doesn't say, but implies the rich higher-ups in the party) Cause and effect: when the money dried up the relationships built on funding were weakened; eventually a large group of populists (the common people) left the party Self-preservation can help explain this breach in partisanship. IRP members' longstanding loyalty to the party means that in the absence of disrupting forces, they can be expected to vote for that party. However, when drastic changes occur in the political and financial landscape, members are responsive to a range of pressures that can weaken their loyalty. Obvious variations occur in such factors as the charisma of the candidates, the impact of economic and domestic policy issues, foreign policy, and especially local economic changes. These factors may well have caused members to dissociate from the IRP. Contrast: normally members remain loyal but when the environment changes loyalty wavers and may break Opinion: the author mentions economic issues twice and mentioned financing several times in previous paragraphs, indicating the importance of money in politics and individual voting behavior Cause and effect: during times of weakened loyalty, various factors (economic issues, personal charisma, local economics) can influence voting patterns Since 1987, the IRP has managed to defeat most of the serious electoral challenges to its central role in Mexican politics. However, by 2002, most believed, correctly, that the IRP-dominated political system was in an advanced state of decay and that a move to greater pluralism in organized political activity was at hand. How this transition period would unfold, and whether it would result in a more participatory and competitive political process for Mexico, was yet to be determined. Traumatic experiences during the nineteenth century, including foreign military occupations, the loss of half of the national territory to the United States, as well as the disillusion sown by a series of unconstitutional regimes, continue to have a profound impact on contemporary political culture. Key terms: greater pluralism Opinion: the author shares the opinion of others that the IRP system of power was decaying by the early 2000s Cause and effect: as the old system broke down, more pluralistic and populist politics were coming into replace it; contemporary political culture is affected by history from earlier centuries Main Idea: Mexican politics were heavily influenced by revolutionary roots, with a strong central government that maintains power through economic power. Economic problems in the 1980's allowed the central rift between commoners and the powerful to worsen until party divisions have now caused the decaying of the IRP.

Passage 2 of CARS with additional information for questions 6-10

Passage 2 (Questions 6 - 10) Giardiasis, caused by the intestinal flagellant protozoa Giardia lamblia, is a common intestinal disease. Giardia are unique in their possession of two nuclei that are similar in appearance, DNA content and transcription. Usually G. lamblia are transmitted by contaminated water with cysts. G. lamblia have seven complex genotypes, but only two genotypes cause human infections. The illness is transmitted by differentiation into infective cysts. Three known cyst wall proteins (CWPs) are highly synthesized in a concerted manner during differentiation into cysts. Key terms: Giardia, genotypes, CWP, two nuclei Cause and effect: disease transmission depends on cyst formation, which depends on CWPs Encystation specific vesicles (ESVs) give the organism the ability to modify or partition cyst wall cargo during secretory transport. These organelles aid the accumulation and maturation of cyst wall material (CWM) composed of at least 3 cyst wall proteins (cwp1-3) complexed with β-(1-3)-N-acetyl-D-galactosamine polymer. CWP is eventually deposited in the plasma membrane of the host's intestinal cells. Trafficking of mature CWM from ESVs to the cell surface, where it forms the cyst wall, is rapid. During cyst formation, a round of DNA replication occurs. Then, nuclear replication takes place, with the DNA divided equally among the resulting 4 nuclei, followed by a second round of DNA replication. Key terms: ESV, CWM, DNA replication, cyst formation Cause and effect: as the CWM levels are increased during infection/cyst formation, the cwp proteins are anchored into the host cell membrane Figure 1 Regulation of cwp abundance within 2-hour transitions during the 14-hour encystation time-course (hpie = hours post initiation of encystations. N = total protein in sample) Figure 1 shows the dominating regulation behavior for each time period; dark = upregulated; light = downregulated At any given time throughout the parasite's lifespan, only one cwp gene is expressed. During an infection, however, the particular cwp gene that is transcribed regularly alternates in a process termed antigenic variation. Both expressed and silent cwp genes are located in the nuclear periphery, but in different specific regions. In expressed cwp genes, promoter histone H4 is acetylated on arginine 6 and trimethylated on arginine 2; in contrast, silent cwp genes include a trimethylated histone H4 at arginine 6. During the homologous recombination in cyst nuclei, type II topoisomerases assist in chromosome replication and tissue development for Giardia differentiation into dormant cysts. In addition, the levels of cyst formation and the cwp1-3 gene expression are increased by Topo II overexpression. Key terms: cwp gene, promoter histone, topoisomerases, cyst differentiation Contrast: the cwp gene switches locations in the nucleus when it actively infects Cause and effect: topo II expression directly correlates to cyst formation levels

Passage 2 of b/c with additional information for questions 6-10

Passage 3 (Questions 11 - 15) A woman began canning her own jams as a hobby. She shared several cans of her jam with her mother for lunch. The next day, her mother was found suffering from blurry vision, difficulty swallowing and troubled breathing. Given the quick progression of symptoms, associated with the new food, the ER physician suspected botulism poisoning. Due to the danger and toxicity of botulism, tests were performed immediately to determine the best course of treatment. Key terms: vision, breathing, botulism Cause and effect: the ingested toxin caused a series of neurologically-based symptoms The botulinum toxin is a neurotoxin produced by the bacterium Clostridium botulinum. Botulism is a life-threatening illness in humans, although forms of the toxin are used for various cosmetic and medical procedures. The eight distinct toxin types are designated A to H. The botulinum toxin protein is a two-chain polypeptide with a 100-kDa heavy chain joined by a disulfide bond to a 50-kDa light chain. This light chain is a protease that attacks one of the fusion proteins (SNARE protein) at a neuromuscular junction, preventing vesicles from anchoring to the membrane to release acetylcholine. Key terms: neurotoxin, 8 types, polypeptide, heavy vs. light chain, ACh Cause and effect: toxin prevent ACh release Figure 1 Mechanism of neuromuscular blockade by botulinum toxin Figure 1 shows the direct effect of the toxin on the neuromuscular junction, where it blocks ACh from activating its receptors Tests employed to detect botulism include brain scans and nerve conduction tests. Toxicity testing of serum specimens, wound tissue cultures, and stool specimen cultures are the best methods for identifying botulism, though they are time-consuming. If the symptoms are diagnosed early, treatment can reduce fatality to less than 20%. A faster way to detect the toxin in humans is using mass spectrometry. Key terms: detection, identification, fatality, clinical effects Cause and effect: earlier detection reduces risk

Passage 3 of b/c with additional information for questions 11-15

Passage 4 (Questions 19 - 23) The quality of DNA-labeled affinity probes is critical in DNA-assisted protein analyses, such as proximity ligation assays (PLA) and immuno-PCR. Efficient, high-performance methods are therefore required for isolation of pure conjugates from reactions where DNA strands have been coupled to antibodies or recombinant affinity reagents. An important step in the synthesis of these molecules is sequentially removing any unconjugated affinity reagents and remaining free oligonucleotides from conjugation reactions as shown in Figure 1. Key terms: probes, DNA, oligonucleotides Cause and effect: removing any unwanted molecules from the nucleotides is a necessary step for purification Figure 1 Illustration of purification of affinity binder-oligonucleotide conjugates Figure 1 outlines the process described in paragraph 2 First, the conjugation is performed in solution by mixing antibodies with an excess of azide-modified oligonucleotides. The resulting mix containing antibody-DNA conjugates and remaining free antibodies and oligonucleotides is incubated, and the products are immobilized on agarose beads. After washes to remove unconjugated antibodies, the captured antibody-DNA conjugates along with unconjugated oligonucleotides are both released by enzymatic cleavage using the restriction enzyme MlyI that cleaves at the border of the complementary region (Figure 2) between the capture and conjugate oligonucleotides to release single-stranded DNA-coupled conjugates. The cleavage process required both ATP and S-adenosyl-L-met in order to run to completion. The eluate was then captured on protein G beads and washes were conducted to remove any free oligonucleotides having no antibodies attached. Finally, purified conjugates were eluted from the protein G beads by lowering the pH. Key terms: azide modification, agarose, MlyI, enzymatic cleavage, protein G, pH Cause and effect: the washes remove unconjugated antibodies and then unconjugated nucleotides to allow for isolation and purification of the oligonucleotide-Ab conjugates These purified high-grade probes extend the capabilities of traditional immunoassays to allow direct detection of proteins and modifications with high specificity and sensitivity. With them, designated protein targets can be readily detected and localized with single molecule resolution and objectively quantified in unmodified cells and tissues. Key terms: specificity, sensitivity Cause and effect: the extensive purification creates an oligonucleotide-Ab conjugate so precise that it can find targets at the level of single-molecule resolution Figure 2 Enzymatic cleavage by MlyI Figure 2 shows the genetic composition of the enzymatic cleavage site

Passage 4 of b/c with additional information for questions 19-23

Passage 5 (Questions 24 - 28) The human digestive tract is fundamentally a long tube running right through the body, with dedicated sections that are capable of digesting material put in at the proximal end and extracting any useful components from it, then expelling the waste products at the terminal end. Key terms: digestive tract function The small intestine is the site where most of the chemical and mechanical digestion is carried out, and where virtually all of the absorption of useful materials is carried out. The intestines also have a smooth muscle wall with two layers of muscle. This enables the generation of rhythmical contractions that force products of digestion through the intestine. To allow for absorption and secretion to take place, specialized zones known as macula communicans exist between the muscle cells. These directly connect the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells. Key terms: small intestine, absorption, contractions, secretion, macula communicans Cause and effect: the MC allows for a direct cytoplasm to cytoplasm connection between cells for easy transport of molecules In the large intestine, these connections allow for the movement of ions and fluids. For example, if material is too solid, it cannot move fluidly and can result in blockage. To prevent this, Cl- ions are secreted into the lumen. Cations and water will trail the chloride anions into the lumen by passing through the intercellular space between the cells. This method of transport is in contrast to typical transcellular transport, where the substances travel through the cell. Key terms: large intestine, ion/fluid movement, intercellular vs. transcellular Contrast: intercellular transport allows the passing of ions between cells, while transcellular transport causes the molecules to travel through the cells Figure 1 Electrolyte transport in the colonic epithelium Diseases of the intestines are often due to chronic inflammation, which can arise from imbalances in the regulation of fluids and solute movement. Elevated levels of enzymes like thymidine kinase are often used to predict the risk of cancer in the colon. Key terms: thyimidine kinase, intestinal diseases, fluid/solute imbalance Cause and effect: imbalances can lead to pathological conditions that elevate enzyme levels, and excess inflammation can increase the risk of cancer

Passage 5 of b/c with additional information for questions 24-28

Passage 5 (Questions 23 - 27) p/s A key modulator of action potential firing is the hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channel. These channels are permeable to both Na+ and K+. The HCN current, Ih, is found in neurons under hyperpolarization of the cell membrane. Ih is proportional to the frequency of firing of action potentials. Key terms: HCN channel, Ih, permeable to ions Cause and effect: Ih is proportional to action potential frequency Neurologists wished to determine if a new drug, Compound X (Figure 1) is able to block Ih and reduce neuropathic pain, providing significant analgesic effects to those with pain. Figure 1 Structure of lidocaine (left) and compound X (right), a potential ion channel blocker Key terms: Compound X, analgesic Cause and effect: Compound X can inhibit Ih to reduce pain Compound X's effect on neuronal firing was first compared to lidocaine, a known sodium channel inhibitor. Ganglion cells were treated with 3 different concentrations of Compound X. Sodium current was isolated and then recorded using patch-clamping. Figure 2 shows the results of these recordings. Figure 2 Na+ current in ganglion neurons treated with Compound X; traces were recorded in the presence and absence (control) of different concentrations of Compound X Key terms: neuronal firing rate, lidocaine, ganglion cells, Na+ current Cause and effect: Figure 2 shows that when compound X was introduced, Na+ current was reduced in all doses, with higher doses reducing current further To test if compound X was indeed also a blocker of HCN channel currents, the effect of the drug on HCN currents in ganglion cell neurons was recorded. HCN channel whole cell current in neurons was induced by giving a membrane potential step from a holding potential of -60 mV step to -140 mV for 700 ms and then back to -70 mV. Solutions of 5 mL each were prepared with differing amounts of compound X. Figure 3 shows the concentration effect of compound X on HCN currents in neurons. Figure 3 Inhibition of HCN currents by addition of compound X Key terms: test HCN blocking, concentration effect Cause and effect: Figure 3 shows that as concentration of X increases, the Ih is inhibited more; the y-axis is (change in current)/(max current)

Passage 5 with additional information for 23-27

Passage 1 of physics and bio Oral drug delivery systems are limited by the short gastrointestinal transit time, leading to low bioavailability. Drug delivery systems able to retain the dosage form in the stomach are needed. Research into floating drug delivery systems (FDDS) may satisfy this need. Key terms: oral delivery systems, limited, FDDS satisfies need Cause and effect: drug quick movement through GI lead to low bioavailability, FDDS may fix FDDS can be approached by either effervescent or non-effervescent techniques. Ideal effervescent techniques achieve floating duration times > 16 hours in the stomach. Effervescent FDDS incorporate gas-generating agents, which provide buoyancy. Newer research focuses on non-effervescent systems, where the swelling of polymers joined to the drug entraps air within the polymeric matrix, providing buoyancy to the dosage form. Key terms: FDDS, effervescent, non-effervescent, buoyancy Contrast: effervescent agents generate gas for buoyancy; non-effervescent ones trap air to do same Cause and effect: release or trapping of gases allows for more buoyant compounds A study was performed on the antidiabetic sulfonylurea glipizide. The drug and one of three polymers were mixed in a mortar according to the ratios described in Table 1. A drop of water was added, and the mixture was kneaded until a homogeneous paste was obtained. The mixture was then placed in an oven at 50°C for 30 min to remove water. The compound was then compressed into tablets which served as the basis for drug release and buoyancy measurements. Key terms: glipizide Cause and effect: the drug-polymer compounds were made into tablets for testing Table 1 shows us that the polymers have different densities and the matrices have different ratios for each trial; we see that polaxemer-188 is less dense than the drug itself and all compounds listed are less dense than water To test in vitro drug release of solid dispersions, the tablets were placed into dissolution vessels containing 900 mL of 0.1 M HCl. Dissolution studies were carried out for one hour, with samples withdrawn at predetermined intervals. Drug concentrations were assayed using HPLC methods. The dissolution experiments were carried out in triplicate, and the results are shown in Figure 1. In vitro buoyancy was also tested. Tablets were placed in a vessel containing 500 mL of 0.1 M HCl. The time taken for the tablet to rise to the surface of the dissolution media (floating lag time) and total duration that the tablet remained on the surface (total floating time) were recorded. Key terms: floating lag time, total floating time Cause and effect: the acidic environment allowed for the production of gas and buoyancy data collection Figure 1 shows that the polaxemer/drug mixture resulted in the lowest drug release rate, presumably due to the enhanced buoyancy and reduced solubility in the aqueous phase The Ksp for glipizide-cyclodextrin in a chyme solution at 37º C was determined to be 5.8 x 10-4. Increased solubility of drug dispersions may be achieved by wetting via hydrophilic polymers, or polymer size reduction. (Note: all pills for the above trials have the same volume.) Key terms: Ksp, increased solubility Cause and effect: using hydrophilic polymers or smaller polymers can raise drug solubility

passage 1 with additional information for questions 1-5 physics

Passage 3 (Questions 14 - 18) p/b β-lactam antibiotics like penicillin are derived from fungi which use the molecules to defend against environmentally-borne diseases. Once discovered, these antimicrobial agents were quickly employed by physicians to treat pathogens which invade humans. These molecules are typically formed via intramolecular attack within an amino acid and secondary reactions between amino acids. The lactam designation refers to the cyclic amide ring found in the molecule. Penicillin-like drugs are analogues of amino acid residues on bacterial cell walls. The structural similarity between β-lactam antibiotics and these residues facilitates their binding to the active sites in the machinery required to build the peptidoglycan wall. Figure 1 Molecular structure of penicillin; the R group can be variable Figure 1 shows the lactam structure and potential sites of attack mentioned in paragraph 1 Key terms: lactam ring, intramolecular attack, similar to amino acid structure Cause and effect: similarity in structure allows the lactam drugs to bind to enzymes used during bacterial cell wall synthesis These β-lactam molecules are particularly reactive due in part to significant ring strain. Nearby nucleophiles can be acylated by the ring, allowing the ring to open. The antimicrobial efficacy of penicillin lies in its ability to acylate serine residues on enzymes that bacteria require for normal cell wall production. During the acylation of serine, the amide on penicillin is converted to an ester. This causes binding and locking of the molecules, which prevents serine from activating the cell wall-synthesizing enzymes. An intact cell wall is necessary for bacteria to stay alive. Key terms: antimicrobial, acylation, conversion to ester Cause and effect: when the ring opens and acylates serine on enzymes, the enzyme is prevented from building the bacterial cell wall Figure 2 Molecular structure of the amino acid serine Figure 2 shows possible nucleophilic sites (side chain OH) that penicillin can attack

passage 3 with additional information for 14-18 p/b

Passage 4 (Questions 19 - 22) p/b Wnt proteins are secreted signal molecules that act as local mediators to control many aspects of development. Wnts are unusual as secreted proteins in that they have a fatty acid chain covalently attached to their N-terminus, which increases their binding to cell surfaces. Wnts can activate the intracellular signaling pathway, the Wnt/β-catenin pathway. The Wnt/β-catenin pathway acts by regulating the proteolysis of the protein β-catenin, which functions in gene regulation. An experiment was performed to test the effect of β-catenin phosphorylation on the rate of degradation. Key terms: Wnt proteins, phosphorylation, catenin Cause and effect: the fatty acid chain helps Wnt bind to cell surfaces; Wnt signals use the β-catenin pathway Mouse cell cultures were treated with radioactive P-labeled phosphate (32PO43-) ions in order to determine if the degraded β-catenin was phosphorylated or not. At various intervals, 5 mL of the cell solution were collected and fractionated with the aid of centrifugation to separate cytoplasmic contents from cellular nuclei. The separated mixtures were then assayed for the presence of 32P. Assay results are summarized in Figure 1. Key terms: radio-labeled Cause and effect: the experiment attempts to quantify the levels of 32P in two different areas of the cell to determine which form of catenin is degraded Figure 1 Results of radioactive phosphate assay (Note: Radioactivity is normalized to total protein content in the sample) Figure 1 shows a contrast in that the cytoplasmic levels of labeled 32P drop off slower and remain significant while the nuclear 32P levels drop to 0 The degradation of cytoplasmic β-catenin depends on a large protein degradation complex, which binds β-catenin and keeps it out of the nucleus while promoting its degradation. Intact β-catenin accumulates and translocates to the nucleus. Once in the nucleus, β-catenin binds to its receptors, displaces the co-repressor Groucho, and acts as a coactivator to stimulate the transcription of Wnt target genes. In the absence of Wnt signaling, most of a cell's β-catenin is located at cell-cell junctions, where it is associated with cadherins, which are transmembrane adhesion proteins. The β-catenin in these junctions helps link the cadherins to the actin cytoskeleton. Any β-catenin not associated with cadherins is rapidly degraded in the cytoplasm. Key terms: degradation, translocation, coactivator Contrast: degraded catenin is kept in cytoplasm by a large protein complex but intact catenin is allowed to enter the nucleus; normally β-catenin is found on the edges of the cell at cell junctions but it can also accumulate and move into the nucleus to activate transcription Cause and effect: nuclear entrance of catenin activates transcription of the target genes Figure 2 Mechanism of intact β-catenin Figure 2 shows the interaction of catenin and its related molecules in gene regulation

passage 4 with additional information for 19-22 p/b