Medical Tests MCAT-TEST Online Practice Questions and Exam Preparation

Medical Tests MCAT-TEST Online Questions & Answers

• Question 731:

  In the United States, breast cancer is the second leading cause of death for women, and as a result, the American Cancer Society, has recommended annual mammography screening for women age 40 years and older. It is estimated that the risk of mortality can be reduced through this procedure by approximately 20-25% during a ten-year period for women age 40 years and older.

  In general, cancer screening behaviors have increased in the United States. According to the National Health Interview Survey, in 1987, approximately 29% of women age 40 years and older reported having had a mammogram in the last 2 years. By 2000, this increased to 70%. However, there are racial disparities, as fewer African American and Hispanic women have mammograms compared to their Caucasian female counterparts. Some studies have looked into these differences. Cultural factors seem to play a role in minority women obtaining fewer mammograms. Asian women, for example, do not like to discuss sensitive topics with strangers.

  Prevention promotions have been designed to increase awareness for the need of breast cancer screening, particularly for women in racial and ethnic minority groups. An innovative breast cancer education program, called the Educational Intervention Asian Grocery Store-Based Education Program, was designed to target Asian women. Located in 20 different Asian grocery stores in communities, the cancer screening exhibits were placed at the entrances of the stores. As Asian women came into the grocery store, health information was passed out to Asian women. Even though only a small amount of women who were considered non-adherents to breast cancer screening ended up scheduling a screening, the study demonstrated an innovative culturally competent approach to health promotion.

  Source: Adapted from G.R. Sadler, P.R. Beerman, K. Lee et al. "Promoting Breast Cancer Screening Among Asian American Women: The Asian Grocery Store Based Cancer Education Program." Copyright 2012 Journal of Cancer Education.

  How would diffusion of innovations theory attempt to explain why African American women get fewer mammograms compared with their Caucasian female counterparts?

  A. African Americans tend to feel stigmatized when they seek medical treatment.
  B. It is possible that African American females experience multiple role conflicts and therefore, they are more likely to relegate their personal needs to the needs of their family.
  C. It is possible that there is pervasive distrust of medical personnel in African-American communities.
  D. Religiosity is a vital ingredient in the fabric of African American lives, and therefore, they will initially opt to see faith healers for their health.
  C. It is possible that there is pervasive distrust of medical personnel in African-American communities.

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  Explanation/Reference:

  C is correct. Everett Rogers' (1962) cultural diffusion of innovations model describes how the diffusion of new ideas can spread directly or indirectly across society. He posited that communities which were more conservative and unwilling to adopt new technology would be slow to accept innovative ideas. Distrust of medical personnel would be a driver for that unwillingness to change. A. This is incorrect. A stigma is a socially discrediting attribute, behavior, or reputation that is assigned to an individual due to that person's belongingness to a particular social group. It usually involves social exclusion or rejection. This does not pertain to diffusion of innovations theory.

  B. This is incorrect. Gender role conflict occurs when people have multiple but incompatible roles associated with their gender. This does not pertain to diffusion of innovations theory. D. This is incorrect. According to Georg Simmel, religiosity is an inner disposition toward the sacred ?faith, for example ?while religion is the objective, organizational form that religiosity assumes in a social world (e.g., churches). This does not pertain to diffusion of innovations theory.

• Question 732:

  Synthetic dyes constitute a commercially significant area of organic chemistry. The color producing properties of these compounds are the result of highly delocalized electron systems giving rise to electronic transitions whose absorptions occur in the visible region. Most commercially useful dyes can be classified as one of three types -- anthraquinones, azo dyes, or triarylmethyl salts. Examples of each type are illustrated in Figure 1.

  

  Figure 1

  In order for a dye to be useful in the fabric industry, it must have sufficient affinity for the polymeric fibers of which the material is composed; the dye must not only impart a color to the fabric, but must also do so in a relatively permanent manner (color fastness). Proper design of synthetic polymers requires the placement of acidic or basic side chains along the polymer backbone such that binding sites are available for dying. Similarly, dyes must be produced not only with the appropriate color-producing structure, but also with an affinity for the fabric in question. The structural units of several common synthetic fibers are shown in Figure 2.

  

  Figure 2

  Cotton is a natural fiber composed of cellulose, a polymer of glucose. Which of the compounds shown in Figure 1 would adhere to a cotton fiber via hydrogen bonding?

  A. Alizarin only
  B. Malachite green only
  C. Alizarin and aniline yellow only
  D. Malachite green, alizarin, and aniline yellow
  C. Alizarin and aniline yellow only

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  Explanation/Reference:

  Hydrogen bonding occurs between OH groups and NH groups in any combination. Since the glucose monomer in cellulose has OH groups, cellulose should be capable of hydrogen bonding to either alizarin, with its two OH groups, or to aniline yellow, with its aromatic amine functionality. Malachite green, on the other hand, has no acidic protons available for hydrogen bonding due to the methylation of the nitrogen atoms.

• Question 733:

  The nuclei of certain unstable isotopes will spontaneously decay, producing a more stable nucleus and releasing a particle or quantity of energy. Alpha decay releases a helium nucleus, beta decay emits an electron, while gamma decay is the emission of a high energy photon. Each type of radioactive decay is characterized, in part, by the half-life of the radioactive material--the time required for half of the nuclei in a sample to undergo decay. Examples of such decays are shown in Figure 1.

  

  Figure 1 A Geiger counter can be used to detect the decay of radioactive materials. A simple Geiger counter consists of a hollow metal cylinder with a wire along its axis. The cylinder is filled with low pressure argon gas and a high voltage difference is applied between the wire and the cylinder. When alpha, beta, or gamma radiation passes through the cylinder, it interacts with the gas particles and leads to the formation of ions which cause a discharge between the wire and the cylinder.

  The consequent current may be used to drive a speaker, producing the characteristic clicking sound of the Geiger counter each time a pulse of current occurs. The Geiger counter circuitry is shown in Figure 2.

  

  Figure 2

  Which of the following statements is true concerning two isolated radioactive samples examined separately with a Geiger counter?

  A. The sample with the shorter half-life will produce a higher frequency of clicks.
  B. The sample with the longer half-life will produce a higher frequency of clicks.
  C. The sample with the shorter half-life will generate a larger current.
  D. The half-life cannot be determined from the click frequency alone.
  D. The half-life cannot be determined from the click frequency alone.

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  Explanation/Reference:

  The half-life indicates the time required for half of a sample to decay and is thus a relative measure of the frequency of decay between two samples of equal mass. However, without knowing the mass, we cannot determine the absolute frequency of decays. A huge sample with a long half-life may produce more decays than a small sample with an extremely short half-life.

• Question 734:

  X-rays are produced by a device which beams electrons with an energy between 103 and 106 eV at a metal plate. The electrons interact with the metal plate and are stopped by it. Much of the energy of the incoming electrons is released in the form of X-rays, which are highenergy photons of electromagnetic radiation. An example of such a device is shown below. Electrons are accelerated from the cathode towards the anode by an electric field.

  

  There are two mechanisms by which the X-rays are produced within the metal. The first mechanism is called bremsstrahlung, which is German for "breaking radiation." X-rays are emitted by the electrons as they are brought to rest by

  interactions with the positive nuclei of the anode.

  The second mechanism occurs when an incoming electron knocks an inner electron out of one of the metal atoms of the anode. This electron is replaced by an electron from a higher energy level of the atom, and a photon making up the

  energy difference is emitted.

  X-rays are absorbed by a material when they pass through it. The amount of X-rays absorbed increases with the density of the material. In addition, lower energy X-rays are more likely to be absorbed than higher energy X-rays. (Note: 1 eV =

  1.6 x 1019 J; Planck's constant h = 4.1 x 10–15 eV•s; speed of light c = 3 x 108 m/s.)

  What is the minimum potential difference required to produce a 0.06 nm X-ray from an electron transition in a metal?

  A. 15,000 V
  B. 20,000 V
  C. 20,500 V
  D. 21,500 V
  C. 20,500 V

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  Explanation/Reference:

  In the passage, we are told that an X-ray is emitted when an electron makes a transition from a higher to a lower energy level in an atom. This question asks us to calculate the minimum potential difference required to produce a 0.06-nm X-ray from an electron transition. First, we have to determine the energy of the X-ray produced. We use the equation E = hc/, where E is the energy, h is Planck's constant, c is the speed of light in a vacuum, and is the wavelength. Substituting in, we get that E = (4.1 x 10-15 x 3 x 108 )/(0.06 x 10-9), which equals 20,500 electron-volts. This is the energy of an X-ray whose wavelength is 0.06 nm, and it is therefore the minimum energy required to create an X-ray with a wavelength of

  0.06 nanometers. This energy comes from accelerating electrons through a potential difference. Now, recall that 1 electron- volt is the energy of an electron accelerated through a potential difference of 1 volt. Therefore 20,500 electron-volts requires that an electron be accelerated through a potential difference of 20,500 volts. So this represents the minimum potential difference required to produce an X-ray with a wavelength of 0.06 nanometers, and answer choice C is correct.

• Question 735:

  Millenialism is, generally speaking, the religious belief that salvation and material benefits will be conferred upon a society in the near future as the result of some apocalyptic event. The term derives from the Latin word for 1,000; in early Christian theology, believers held that Christ would return and establish his kingdom on earth for a period of a thousand years.

  Millenialist movements, Christian and non-Christian, have arisen at various points throughout history, usually in times of great crisis or social upheaval. In "nativistic" millenialist movements, a people threatened with cultural disintegration attempts to earn its salvation by rejecting foreign customs and values and returning to the "old ways". One such movement involving the Ghost Dance cults, named after the ceremonial dance which cult members performed in hope of salvation, flourished in the late 19th century among Indians of the western United States.

  By the middle of the 19th century, western expansion and settlement by whites was seriously threatening Native American cultures. Mining, agriculture and ranching encroached on and destroyed many Indian land and food sources. Indian resistance led to a series of wars and massacres, culminating in the U.S. Government's policy of resettlement of Indians onto reservations which constituted a fraction of their former territorial base. Under these dire circumstances, a series of millenialist movements began among western tribes.

  The first Ghost Dance cult arose in western Nevada around 1870. A Native American prophet named Wodziwob, a member of a Northern Paiute tribe, received the revelation of an imminent apocalypse which would destroy the white man, restore all dead Indians to life, and return to the Indians their lands, food supplies (such as the vanishing buffalo), and old way of life. The apocalypse was to be brought about with the help of a ceremonial dance and songs, and by strict adherence to a moral code which, oddly enough, strongly resembled Christian teaching. In the early 1870s, Wodziwob's Ghost Dance cult spread to several tribes in California and Oregon, but soon died out or was absorbed into other cults.

  A second Ghost Dance cult, founded in January 1889, evolved as the result of a similar revelation. This time Wovoka -- another Northern Paiute Indian, whose father had been a disciple of Wodziwob -- received a vision during a solar eclipse in which he died, spoke to God, and was assigned the task of teaching the dance and the millennial message. With white civilization having pushed western tribes ever closer to the brink of cultural disintegration during the previous twenty years, the Ghost Dance movement spread rapidly this time, catching on among tribes from the Canadian border to Texas, and from the Missouri River to the Sierra Nevadas -- an area approximately one-third the size of the continental United States.

  Wovoka's Ghost Dance doctrine forbade Indian violence against whites or other Indians; it also involved the wearing of "ghost shirts," which supposedly rendered the wearers invulnerable to the white man's bullets. In 1890, when the Ghost Dance spread to the Sioux Indians, both the ghost shirts and the movement itself were put to the test. Violent resistance to white domination had all but ended among the Sioux by the late 1880s, when government- ordered reductions in the size of their reservations infuriated the Sioux, and made them particularly responsive to the millenialist message of the Ghost Dance. As the Sioux organized themselves in the cult of the dance, an alarmed federal government resorted to armed intervention which ultimately led to the massacre of some 200 Sioux men, women and children at Wounded Knee, South Dakota in December of 1890. The ghost shirts had been worn to no avail, and Wounded Knee marked the end of the second Ghost Dance cult.

  The passage implies that a paradoxical element of the Ghost Dance cults was their:

  A. organized resistance to cultural change.
  B. mixture of anti-white sentiment and Christian morality.
  C. belief in the ability of "ghost shirts" to protect them in combat.
  D. combination of millenialist message and desire to revive the "old ways".
  B. mixture of anti-white sentiment and Christian morality.

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  Explanation/Reference:

  This asks what was paradoxical about the Ghost Dance cults. A paradox is something that seems to be contradictory and yet is true. The correct answer, choice (B), can be found paragraph 3. In explaining the doctrine of the first Ghost Dance cult, the author notes that, although the point of the dance was to destroy the white man and foster a return to the old ways, believers were instructed to follow a strict code of morality that, "oddly enough, strongly resembled Christian teaching." The paradox of the Ghost Dance was that it borrowed the moral teachings of the people it hoped to destroy, so choice (B) is our answer. There is nothing paradoxical about choice (A). As defined in the first paragraph, a nativistic millenialist movement like the Ghost Dance is designed to unite a people threatened with cultural disintegration. Choice (C) describes an irrational element of the Ghost Dance religion, not a paradoxical one. Practically all religions are based on one or more articles of faith, and the Indians' belief that "ghost shirts" would protect them in combat was a straightforward, if doomed, element of their cult doctrine. Choice (D) is wrong because there's nothing odd or contradictory in combining a millenialist message with a desire to revive the "old ways". As the author says in paragraph 1, the desire to revive old ways is a defining characteristic of nativistic millenialist movements.

• Question 736:

  The Earth's atmosphere reaches hundreds of kilometers above the surface of the planet. The lowest layer, the troposphere, extends from the ground to a height of approximately 12 km. Air pressure within the troposphere decreases with height above the ground, accompanied by a parallel trend in air density. The decrease in density has important consequences for the dissipation of air pollution from industrial smoke stacks. The gas from the stack is typically hotter and less dense than the surrounding air and rises. As a parcel of hot air rises, it expands approximately adiabatically doing work on the surrounding air. This results in a decrease in both its temperature and its density.

  

  Figure 1 A smoke stack functions to expel gaseous waste products from a chemical process. It is also an important means of removing heat from a reaction mixture. The heat corresponding to a change in temperature of a gas at constant pressure is

  

  given by , where is the heat added to the gas, n is the number of moles of gas, is the molar heat capacity of a particular gas at constant pressure, and T is the change in temperature. At atmospheric pressure, the

  

  molar heat capacity for steam, O (g) is approximately four times that of air.

  According to Figure 1, what is the approximate relationship between the energy content of a liter of air at 12 km and that of a liter of air at 120 km?

  A. The energy content in a liter at 12 km is greater because the mass is greater.
  B. The energy content in a liter at 120 km is greater because the temperature is higher.
  C. The energy content in a liter at 120 km is greater because the air is less dense.
  D. The energy contents are equal because the volumes are equal.
  A. The energy content in a liter at 12 km is greater because the mass is greater.

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  Explanation/Reference:

  Looking at Figure 1, we see that the temperature at 120 km is significantly higher than at 12 km.

  

  However, the graph also indicates that the pressure at 120 km is essentially zero. The passage indicates that as the pressure decreases, so does the density. Thus, the mass of a liter of air at this altitude is near zero and the energy content of the air is minimal, regardless of the higher temperature. You may also rearrange the ideal gas law to obtain:

  

  which tells you that as P approaches zero, so does n/V, which is an indication of density.

• Question 737:

  If a man having blood group AB marries a woman who is heterozygous for blood group, what is the probability of their first child having blood group B?

  A. 100%
  B. 50%
  C. 25%
  D. 0%
  B. 50%

• Question 738:

  Given the reduction potentials for the following half-reactions:

  Br2 (l) + 2e? 2 Br?aq) Eored= + 1.07 V

  Au3+ (aq) + 3 e? Au (s) Eored= + 1.55 V

  What is the electrochemical potential for the following chemical reaction?

  2Au3+ (aq) + 6Br?aq) 3Br2 + 2Au (s)

  Eocell = ?

  A. Eo= -0.48 V
  B. Eo= -0.11 V
  C. Eo= +0.11 V
  D. Eo= +0.48 V
  D. Eo= +0.48 V

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  Explanation/Reference:

  This question is testing your understanding of electrochemical cells and using half-reactions to determine the cell potential. To answer this question, you must first know that the electrochemical potential for a cell is equal to the reduction

  potential plus the oxidation potential:

  Eocell = Eored + Eoox

  In this chemical reaction, Au3+ is reduced to Au making this the reduction half-reaction (Eored= + 1.55 V). Oppositely, Br?is oxidized to Br2, so this would be the oxidation half-reaction.

  Therefore, you must reverse the reduction potential given for Br2 so that it matches the chemical reaction given, as follows:

  2Br?aq) Br2 (l) + 2e?Eoox= ?Eored= -(+1.07 V) = -1.07 V

  Therefore, the Eocell = Eored + Eoox = (+1.55 V) + (-1.07 V) = + 0.48 V, making D the correct answer.

  Note:

  When calculating the cell potentials, do not multiply the reduction potential or oxidation potential by the coefficients.

• Question 739:

  Early experimentation on the single-celled organism Acetabularia led to important discoveries about the role of the nucleus in regulating cell function. Acetabularia is an enormous single cell with three distinct regions: a cap, a root-like rhizoid,

  and a stalk which connects the two. The following experiments were conducted to study the development of the cell:

  Experiment 1

  The stalk of an Acetabularia was cut, fragmenting the cell. The fragment which included the cap died shortly afterwards while the fragment containing the rhizoid regenerated to form a complete Acetabularia.

  Experiment 2

  The nucleus from Acetabularia mediterranea, which has a flat cap, was transplanted into Acetabularia crenulata, which has a tufted cap, following removal of the Acetabularia crenulata nucleus. The Acetabularia crenulata cap eventually

  assumed the flat shape.

  Experiment 3

  The nucleus of Acetabularia mediterranea was removed from the young cell before it first formed a cap. A normal cap formed several weeks later. The cell proved to be inviable and died shortly thereafter.

  Experiment 4

  A young Acetabularia was fractioned into a number of portions before it first formed a cap. Several weeks later, both the portion containing the nucleus and the portion containing the apical tip of the stalk formed caps. The other portions did

  not form caps.

  The mRNA sequence shown below is transcribed from which of the following DNA fragments?

  z5'-UGUAAUC-3'

  mRNA

  A. 5'-GAUUACA-3'
  B. 5'-ACATTAG-3'
  C. 5'-CTAATGT-3'
  D. 5'-GATTACA-3'
  D. 5'-GATTACA-3'

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  Explanation/Reference:

  mRNA is transcribed through complementary base pairing from the template strand of DNA. The sequence of mRNA runs antiparallel to the strand of DNA from which it was synthesized. The base pairs in DNA bind to base pairs in RNA in the following way -- G-C, C-G, A-U, T-A. Note that RNA contains uracil in place of thymine. The complementary strand of DNA to the given mRNA is:

  

  

  The DNA strand above must be rewritten in the 5' 3' direction to fit the answer choices.

  

  Choice A is incorrect because there is no uracil in DNA.

  Choice B is incorrect because the sequence is backwards. Note that the strands must be antiparallel. Choice C is incorrect because the base pairs are not complementary.

• Question 740:

  Which of the following compounds share the same absolute configuration?

  

  A. I and III
  B. II and IV
  C. I and II
  D. II, III, and IV
  B. II and IV

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  Explanation/Reference:

  This question asks you to compare the absolute configurations of four compounds which are in the form of Fischer projections. There are certain rules which you need to be familiar with in order to decipher the absolute configuration. First, the substituent with the lowest priority must be positioned vertically, that is, either up or down. Remember that in 3-D terms, vertical lines represent bonds going into the page. Second, to move your diagram around on the page you have to remember that interchanging any two pairs of substituents will give you the same compound -- that is, it will preserve the absolute configuration. Interchanging just ONE pair of substituents will always REVERSE the absolute configuration. Also, you can hold one group steady while rotating the other three clockwise or counterclockwise. The third rule is that once you have the lowest-priority group positioned vertically, you should determine the order of priority among the other three substituents. If that order increases clockwise, that means the chiral carbon has an R configuration, while if it increases counterclockwise, the chiral carbon has an S configuration. If you look at compound I, you can see that the order of increasing priority is hydrogen, methyl, carboxyl, and hydroxyl. In order to get the hydrogen into a vertical position, you can hold the methyl group steady and rotate the others by 90? The order of increasing priority is clockwise and so the configuration is R, for compound II, the hydrogen is already placed vertically, so you don't have to worry about moving the molecule around the page. The order of increasing priority is hydrogen, methyl, carboxyl and amine, so when you draw arrows between the last three, the direction is counterclockwise and so the configuration is S. Therefore, you can discard choice C since these two molecules have opposite configurations. Compound III may catch you off guard, because if you look at this molecule closely you can see that it is achiral. Although they are written differently, there are two ethyl substituents in this molecule, therefore this molecule is neither R nor S, and so choices A and D can be eliminated. This leaves choice B, but let's just look at compound IV anyway. Again, the hydrogen is positioned vertically and the order of priority is the same as in compound I. However, if you connect the arrows this time, you can see that the direction is counterclockwise and so the configuration is S. This makes compounds II and IV the same, and so choice B is correct.