Medical Tests MCAT-TEST Online Practice Questions and Exam Preparation

Medical Tests MCAT-TEST Online Questions & Answers

• Question 391:

  A body is projected with high velocity at 45o (angle) with ground, which falls after 15 seconds, its horizontal component of velocity during its motion will:

  A. increase.
  B. decrease.
  C. remain constant.
  D. first decrease then increase.
  C. remain constant.

• Question 392:

  Although we know more about so-called Neanderthal men than about any other early population, their exact relation to present-day human beings remains unclear. Long considered sub-human, Neanderthals are now known to have been fully human. They walked erect, used fire, and made a variety of tools. They lived partly in the open and partly in caves. The Neanderthals are even thought to have been the first humans to bury their dead, a practice which has been interpreted as demonstrating the capacity for religious and abstract thought. The first monograph on Neanderthal anatomy, published by Marcelling Boule in 1913, presented a somewhat misleading picture. Boule took the Neanderthals' lowvaulted cranium and prominent brow ridges, their heavy musculature, and the apparent overdevelopment of certain joints as evidence of a prehuman physical appearance. In postulating for the Neanderthal such "primitive" characteristics as a stooping, bent-kneed posture, a rolling gait, and a forward-hanging head, Boule was a victim of the rudimentary state of anatomical science. Modern anthropologists recognize the Neanderthal bone structure as that of a creature whose bodily orientation and capacities were very similar to those of present-day human beings. The differences in the size and shape of the limbs, shoulder blades, and other body parts are simply adaptations which were necessary to handle the Neanderthal's far more massive musculature. Current taxonomy considers the Neanderthals to have been fully human and thus designates them not as a separate species, Homo neanderthalensis, but as a subspecies of Homo sapiens: Homo sapiens neanderthalensis. The rise of the Neanderthals occurred over some 100,000 years -- a sufficient period to account for evolution of the specifically Neanderthal characteristics through free interbreeding over a broad geographical range. Fossil evidence suggests that the Neanderthals inhabited a vast area from Europe through the Middle East and into Central Asia from approximately 100,000 years ago until 35,000 years ago. Then, within a brief period of five to ten thousand years, they disappeared. Modern human, not found in Europe prior to about 33,000 years ago, thenceforth became the sole inhabitants of the region. Anthropologists do not believe that the Neanderthals evolved into modern human beings. Despite the similarities between Neanderthal and modern human anatomy, the differences are great enough that, among a population as broad-ranging as the Neanderthals, such an evolution could not have taken place in a period of only ten thousand years. Furthermore, no fossils of types intermediate between Neanderthals and moderns have been found. A major alternative hypothesis, advanced by E. Trinkaus and W.W. Howells, is that of localized evolution. Within a geographically concentrated population, free interbreeding could have produced far more pronounced genetic effects within a shorter time. Thus modern human could have evolved relatively quickly, either from Neanderthals or from some other ancestral type, in isolation from the main Neanderthal population. These humans may have migrated throughout the Neanderthal areas, where they displaced or absorbed the original inhabitants. One hypothesis suggests that these "modern" humans immigrated to Europe from the Middle East. No satisfactory explanation of why modern human beings replaced the Neanderthals has yet been found. Some have speculated that the modern humans wiped out the Neanderthals in warfare; however, there exists no archeological evidence of a hostile encounter. It has also been suggested that the Neanderthals failed to adapt to the onset of the last Ice Age; yet their thick bodies should have been heat-conserving and thus well-adapted to extreme cold. Finally, it is possible that the improved tools and hunting implements of the late Neanderthal period made the powerful Neanderthal physique less of an advantage than it had been previously. At the same time, the Neanderthals' need for a heavy diet to sustain this physique put them at a disadvantage compared to the less massive moderns. If this was the case, then it was improvements in human culture -- including some introduced by the Neanderthals themselves -- that made the Neanderthal obsolete.

  Boule considered all of the following to be evidence that Neanderthals were sub-human EXCEPT their:

  A. posture.
  B. bone structure.
  C. cranial structure.
  D. ability to use tools.
  D. ability to use tools.

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  Explanation/Reference:

  The characteristics which Boule took as evidence that the Neanderthals were subhuman are listed in Paragraph 3. Choice D is correct because Boule never cites the use of tools as evidence of subhuman development.

• Question 393:

  Which of the following molecules is a hormone capable of creating physiological and anatomical changes during adolescence which will last a person's entire life?

  B

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  Explanation/Reference:

  A: Polypeptide. Note all of the amide bonds. This polypeptide is vasopressin.

  B: Classic four-ring steroid structure. This is estradiol.

  C: Sugar ring attached to nitrogenous base makes this a nucleotide. This is cytosine monophosphate.

  D: Lengthy carbon chains attached to a phosphate group indicates a phospholipid.

• Question 394:

  The simple harmonic motion of a mass suspended from vertical springs is investigated in two experiments. The springs used in both experiments have a spring constant k and a natural length L0. The material used to make the springs has a

  Young's modulus of 2 x 1011 Pa.

  In the first experiment a mass m is suspended from a spring. The mass stretches the spring to a new length L, called the equilibrium length.

  In the second experiment the mass m is suspended from two identical springs as shown in Figure 2 below. When the mass m is in equilibrium, each spring is stretched from its natural length by the same amount xe.

  In both experiments the masses of the springs are negligible, and the elastic limits of the springs are never exceeded.

  

  The two springs in Experiment 2 are replaced by a single spring having a spring constant k' such that the equilibrium length xe does not change. What is the ratio of k' to k?

  

  A. Option A
  B. Option B
  C. Option C
  D. Option D
  D. Option D

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  Explanation/Reference:

• Question 395:

  At a recent meeting of the American Public Transit Association, the Environmental Protection Agency unveiled stringent new standards for pollution control. The transit authorities were particularly concerned about the implementation of a proposed "Clean Air Act." They believed the provisions of the Clean Air Act could severely affect basic services to their local communities. Many transit agencies were concerned that it would be difficult to comply with the pollution and emissions control standards while continuing to operate within realistic budgets. The aim of the Clean Air Act is to assure that by the year 2000, there will be a reduction of at least 10 million tons of sulfur dioxide from 1980 levels. The bill also calls for a reduction in pollutants that contribute to the depletion of ozone. Strict regulations of toxic air emissions would have to be established and enforced. Additionally, the Clean Air Act would establish specific acid-rain reduction quotas and enforce severe penalties for transgressors of any of the new clean air regulations. There is little doubt that mass-transit suppliers will be considerably affected by this new legislation, just as the chemical and petroleum industries have already been affected by similar legislation. Transit authorities are challenged to strike a difficult balance between complying with the government's new standards and developing an official concern for the environment, while continuing to fulfill the transportation needs of the general population. Among the areas addressed by the Clean Air Act, the topic of mobile resources is of particular interest to mass transit authorities. Provisions contained in the Act under this title are aimed at encouraging the development and practical use of alternative fuel sources, like solar energy and methane fuel. The goal of this section of the Act is to eradicate toxic fuel emissions in order to provide cleaner air and a more favorable environment. The Act even goes so far as to declare that in cities like New York, Los Angeles and Houston -- where air quality is particularly noxious and toxins exceed the limits of federal regulations -- forms of mass transit should run on so-called "clean-burning fuels" by the year 2000. Such fuels include reformulated gasoline, propane, electricity, natural gas, ethanol, methanol, or any similar type of low-emission fuel. In addition, the Act proposes that, by 1994, all new urban buses in cities with populations exceeding one million must operate solely on clean-burning fuels. The topics of alternative fuels and alternative fuel vehicles represent, by far, the most controversial issue in the Clean Air Act. President Bush has called alternative fuels "bold and innovative" means to control pollution, but according to many transportation experts, the Act's proposals on alternative fuel usage are unrealistic. The transit authorities recognize that concern for the environment and health hazards like pollution are global issues. However, most transit officials concur that inventing and developing new ways to fuel mass transit will take at least 50 years to realize. They point out that the Act does not mention the political and social ramifications of usurping the role of the petroleum industries. The Act does not mention if or how the thousands of people employed by the oil industry will get retrained to produce and implement the use of "clean" fuel. No one disputes the fact that people need some form of transportation to get from place to place. Preserving the environment should be a priority, yet we need to remember that even if toxic emissions are completely eliminated sometime in the future, the challenge of moving mass numbers of people where they want to go will still exist and must remain a priority. Transit authorities contend that unless the Clean Air Act also acknowledges this, and develops a way to encourage mass transit over personal transportation, the problems of pollution might not be significantly altered. They suggest that there are many areas in this country that have little or no mass transit and that, if the Clean Air Act's goal is to reduce pollution, perhaps the most practical and realistic means to achieve that goal is to encourage the development and maintenance of mass transit systems.

  In general, transit authorities feel that complying with the provisions in the Clean Air Act will:

  A. be fairly easy as long as strict compliance is followed by all agencies of mass transit.
  B. prove difficult because only wealthy private corporations can afford to drastically change their methods of business.
  C. demand an increase in government funding for mass transit.
  D. be challenging because transit authorities must meet the public's transportation needs while adhering to the new provisions.
  D. be challenging because transit authorities must meet the public's transportation needs while adhering to the new provisions.

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  Explanation/Reference:

  In the third paragraph, the author states that transportation agencies will find it challenging to strike a balance between complying with the government's new standards and continuing to fulfill the transportation needs of the general public

  (Choice D).

  Choice A is incorrect because it contradicts the whole theme of the passage, i.e. that compliance with the provisions of the Act will be difficult for transit agencies. Choice C can be ruled out because government funding for mass transit is not

  discussed anywhere in the passage. Similarly, Choice B is out because the abilities of wealthy private corporations to change their methods of business is not discussed by the author.

• Question 396:

  The simple harmonic motion of a mass suspended from vertical springs is investigated in two experiments. The springs used in both experiments have a spring constant k and a natural length L0 . The material used to make the springs has a

  Young's modulus of 2 x 1011 Pa.

  In the first experiment a mass m is suspended from a spring. The mass stretches the spring to a new length L, called the equilibrium length.

  In the second experiment the mass m is suspended from two identical springs as shown in Figure 2 below. When the mass m is in equilibrium, each spring is stretched from its natural length by the same amount xe.

  In both experiments the masses of the springs are negligible, and the elastic limits of the springs are never exceeded.

  

  If the spring in Experiment 1 was suspended from the ceiling of an elevator accelerating with acceleration a, how would the equilibrium length of the spring compare to the equilibrium length of the spring when the elevator is stationary?

  A. The equilibrium length of the spring would be greater when the elevator is accelerating upward.
  B. The equilibrium length of the spring would be greater when the elevator is stationary.
  C. The equilibrium length of the spring would be greater when the elevator is accelerating downward with acceleration smaller than the acceleration due to gravity.
  D. The equilibrium length of the spring doesn't depend on the acceleration of the elevator.
  A. The equilibrium length of the spring would be greater when the elevator is accelerating upward.

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  Explanation/Reference:

• Question 397:

  The body compensates for increased environmental temperature by:

  A. decreasing salt retention.
  B. increasing respiration rate.
  C. increasing heart rate.
  D. increasing water lost through skin.
  D. increasing water lost through skin.

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  Explanation/Reference:

  The body compensates for increased environmental temperature by sweating and losing water through the skin. Respiration and heart rate increase during exercise in response to internal demand for more oxygen. Salt retention has little to do with environmental temperature.

• Question 398:

  One of the most common methods that scientists use to determine the age of fossils is known as carbon dating. 14C is an unstable isotope of carbon that undergoes beta decay with a half-life of approximately 5,730 years. Beta decay occurs when a neutron in the nucleus decays to form a proton and an electron which is ejected from the nucleus. 14C is generated in the upper atmosphere when 14N, the most common isotope of nitrogen, is bombarded by neutrons. This mechanism yields a global production rate of 7.5 kg per year of 14C, which combines with oxygen in the atmosphere to produce carbon dioxide. Both the production and the decay of 14C occur simultaneously. This process continues for many half-lives of 14C, until the total amount of 14C approaches a constant. A fixed fraction of the carbon ingested by all living organisms will be 14C. Therefore, as long as an organism is alive, the ratio of 14C to 12C that it contains is constant. After the organism dies, no new 14C is ingested, and the amount of 14C contained in the organism will decrease by beta decay. The amount of 14C that must have been present in the organism when it died can be calculated from the amount of 12C present in a fossil. By comparing the amount of 14C in the fossil to the calculated amount of 14C that was present in the organism when it died, the age of the fossil can be determined. The bones of a living human adult contain about 8 grams of 14C at any given time. If a prehistoric human adult skeleton is found to contain 1 gram of 14C, what is the approximate age of the fossil?

  A. 5,730 years
  B. 17,190 years
  C. 34,380 years
  D. 45,840 years
  A. 5,730 years

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  Explanation/Reference:

  The passage states that after death, the 14C in a skeleton that beta decays is not replaced by new 14C. Consequently, as time passes, the amount of 14C in the skeleton decreases. The half-life quantifies the rate of this decrease. The half-life of an isotope is the length of time it takes for half of the atoms in a sample of that isotope to decay. A skeleton starts out with 8 g of 14C, and the half-life of 14C is 5,730 years. Therefore, after 5,730 years, 8 g of 14C will decay to 4 g. After another 5,730 years, 4 g will decay to 2 g, and after yet another 5,730 years, 2 g will decay to 1 g, which is the amount present in the prehistoric skeleton. Hence, the prehistoric skeleton must be 3(5,730) = 17,190 years old, and choice B is correct.

• Question 399:

  The Russia which emerged from the terrible civil war after the 1917 Revolution was far from the Bolsheviks' original ideal of a non-exploitative society governed by workers and peasants. By 1921, the regime was weakened by widespread famine, persistent peasant revolts, a collapse of industrial production stemming from the civil war, and the consequent dispersal of the industrial working class -- the Bolsheviks' original base of support. To buy time for recovery, the government in 1921 introduced the New Economic Policy, which allowed private trade in farm products (previously banned) and relied on a fixed grain tax instead of forced requisitions to provide food for the cities. The value of the ruble was stabilized. Trade unions were again allowed to seek higher wages and benefits, and even to strike. However, the Bolsheviks maintained a strict monopoly of power by refusing to legalize other parties. After the death of the Revolution's undisputed leader, Lenin, in January 1924, disputes over the long-range direction of policy led to an open struggle among the main Bolshevik leaders. Since open debate was still possible within the Bolshevik Party in this period, several groups with differing programs emerged in the course of this struggle. The program supported by Nikolai Bukharin -- a major ideological leader of the Bolsheviks with no power base of his own -- called for developing agriculture through good relations with wealthy peasants, or "kulaks." Bukharin favored gradual industrial development, or "advancing towards Socialism at a snail's pace." In foreign affairs, Bukharin's policy was to ally with non-Socialist regimes and movements that were favorable to Russia. A faction led by Leon Trotsky, head of the Red Army and the most respected revolutionary leader after Lenin, called for rapid industrialization and greater central planning of the economy, financed by a heavy tax on the kulaks. Trotsky rejected the idea that a prosperous, human Socialist society could be built in Russia alone (Stalin's slogan of "Socialism in One Country"), and therefore called for continued efforts to promote working-class revolutions abroad. As time went on, he became bitterly critical of the new privileged elite emerging within both the Bolshevik Party and the Russian state. Joseph Stalin, General Secretary of the Bolshevik Party, was initially considered a "center," conciliating figure, not clearly part of a faction. Stalin's eventual supremacy was ensured by three successive struggles within the party, and only during the last did his own program become clear. First, in 1924?5, Stalin isolated Trotsky, allying for this purpose with Grigori Zinoviev and Lev Kamenev, Bolshevik leaders better known than Stalin himself, whom Trotsky mistakenly considered his main rivals. Stalin maneuvered Trotsky out of leadership of the Red Army, his main potential power base. Next, Stalin turned on Zinoviev and Kamenev, using his powers as head of the Party organization to remove them from party leadership in Leningrad and Moscow, their respective power bases. Trotsky, Zinoviev, and Kamenev then belatedly formed the "Joint Opposition" (1926?7). With Bukharin's help, Stalin easily outmaneuvered the Opposition: Bukharin polemicized against Trotsky, while Stalin prevented the newspapers from printing Trotsky's replies, organized gangs of toughs to beat up his followers, and transferred his supporters to administrative posts in remote regions. At the end of 1927, Stalin expelled Trotsky from the Bolshevik Party and exiled him. (Later, in 1940, he had him murdered.) Zinoviev and Kamenev, meanwhile, recanted their views in order to remain within the Party. The final act now began. A move by kulaks to gain higher prices by holding grain off the market touched off a campaign against them by Stalin. Bukharin protested, but with the tradition of Party democracy now all but dead, Stalin had little trouble silencing Bukharin. Meanwhile, he began a campaign to force all peasants -- not just kulaks -- onto state-controlled "collective farms," and initiated a crash industrialization program during which he deprived the trade unions of all rights and cut real wages by 50%. Out of the factional struggle in which he emerged by 1933 as sole dictator of Russia, Stalin's political program of building up heavy industry on the backs of both worker and peasant emerged with full clarity.

  According to the passage, a similarity between Stalin and Trotsky was their attitude and policy toward:

  A. the elite of the Bolshevik Party.
  B. the importance of industrialization.
  C. democracy within the party.
  D. trade unions.
  B. the importance of industrialization.

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  Explanation/Reference:

  Details of Trotsky's and Stalin's policies and attitudes can be found in Paragraphs 4 and 7. Trotsky called for rapid industrialization and Stalin sought to build up heavy industry, so it's clear that industrialization was important to both of them

  (Choice B).

  Choice A is incorrect; the author states that Trotsky was critical of the elite, but Stalin's attitude toward them is left unstated. Similarly, you don't know how either of them felt about democracy within the party (Choice C) or how Trotsky felt

  about trade unions (Choice D), so these choices are wrong.

• Question 400:

  Which type of DNA mutation involves the insertion of extra base pairs into the sequence?

  A. inversion
  B. substitution
  C. addition
  D. deletion
  C. addition

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  Explanation/Reference:

  Addition involves the insertion of extra base pairs into the DNA sequence.