Medical Tests MCAT-TEST Online Practice Questions and Exam Preparation

Medical Tests MCAT-TEST Online Questions & Answers

• Question 101:

  Every atomic orbital contains plus and minus regions, defined by the value of the quantum mechanical function for electron density. When orbitals from different atoms overlap to form bonds, an equal number of new molecular orbitals results. These are of two types: or bonding orbitals, formed by overlap between orbital regions with the same sign, and antibonding * or * orbitals, formed by overlap between regions with opposite signs. Bonding orbitals have lower energy than their component atomic orbitals, and antibonding orbitals have higher energy. The electron pairs reside in the lower-energy bonding orbitals; the higher-energy, less stable orbitals remain empty when the molecule is in its ground state. A benzene ring has six unhybridized pz orbitals (one from each carbon atom), which together from six molecular orbitals, each one delocalized over the entire ring. Of the possible orbital structures for benzene, the one with the lowest energy has the plus region of all six p orbital functions on one side of the ring. The six electrons occupying the orbitals fill the three most stable molecular orbitals, leaving the other three empty. Molecular orbitals are filled from the lowest to the highest energy level. The number of bonds between atoms is determined by the number of filled bonding orbitals minus the number of filled antibonding orbitals; each antibonding orbital cancels out a filled bonding orbital. For a diatomic molecule, orbitals in the n = 2 energy level are filled as follows:

  

  (equal in energy), and * (equal in energy), *2 . (The designation of the three p orbitals as , , and are interchangeable.) Absorption of a photon can raise an electron to a higher-energy molecular orbital. The excited electron does not immediately change its spin, which is opposite to that of the electron with which it was previously paired. This singlet state is relatively unstable: the molecule may interact with another molecule, or fluoresce and return to its ground state. Alternatively, there may be a change in spin direction somewhere in the system; the molecule then enters the so-called triplet state, which generally has lower energy. The molecule now cannot return quickly to its ground state, since the excited electron no longer has a partner of opposite spin with which to pair. It also cannot return to the singlet state, because the singlet has greater energy. Consequently, the triplet state, which has two unpaired electrons in separate orbitals, is long-lived by atomic standards, with a lifetime that may be ten seconds or more. During this period, the molecule is highly reactive.

  Given the order in which orbitals are filled, which molecule is a triplet in its ground state?

  

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

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  Explanation/Reference:

  The answer to this question is found in the passage: You are given the order of orbital filling in paragraph three and are told in the last paragraph what a triplet state is. Remember that when there are orbitals of equal energy, each one will be half-filled before any of the orbitals is completely filled, and all the half-filled orbitals will have electrons with the same spin. Looking at the answer choices for the question, you can see that they are all diatomic; thus, there will be two electrons in a hydrogen molecule, fourteen in nitrogen, sixteen in oxygen and eighteen in fluorine. The passage does not describe how to fill the n = 1 shell, but from knowing that the n = 2 shell has the sigma 2s bonding orbitals and one sigma 2s antibonding orbital, there will be sigma bonding and antibonding orbitals in the n = 1 shell, and these will also hold four electrons. Therefore, molecular hydrogen will fill half the n = 1 shell with the total of two electrons that it has and there will be zero electrons in its second shell. Working in a similar way you will have ten electrons in the second shell for molecular nitrogen, twelve for oxygen, and fourteen for fluorine. When you fill in the molecular orbitals, you will find that nitrogen just fills the pi 2x and 2y bonding orbitals. Since there are no unpaired electrons, molecular nitrogen can't be a triplet. Molecular oxygen has two extra electrons, which go into the pi 2x and 2y antibonding orbitals. In other words, it has unpaired electrons with the same spin. If you’re not sure, check the final choice: In fluorine, these pi 2x and 2y antibonding orbitals are filled with the two extra electrons, so fluorine is not a triplet. Thus, it turns out that the oxygen molecule is a triplet in its ground state, so choice B is the correct answer.

• Question 102:

  A hovercraft is a versatile vehicle capable of traveling over land, water, or any other essentially flat surface. The hovercraft consists of a body or hull onto which a rotor (lift fan) is mounted. The lift fan provides the vertical lift by propelling air into an area beneath the hovercraft called the skirt. The pocket of air in the skirt supports the moving hovercraft and reduces the friction between the vehicle and the ground to almost zero. As such, there is no contact between the hovercraft and the ground.

  A second fan, which generates a horizontal thrust, propels the hovercraft forward. Rudders which direct the airflow from this second fan are used by the pilot to control the movement of the hovercraft. The horizontal movement of the

  

  hovercraft is opposed by air resistance which generates aerodynamic drag.

  The horizontal thrust fan of a hovercraft traveling across a frozen lake in a large circle suddenly fails. Which of the following best describes the path of the hovercraft (as one looks down from above) immediately following thrust fan shutoff?

  

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

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  Explanation/Reference:

  When the thrust fan is shut off, there will no longer be a centripetal force to sustain the hovercraft in its circular motion. Thus, it will proceed in a straight line tangent to its path at the moment the fan is turned off.Choice B is incorrect because a force (centripetal force) is required to cause an object to move in a circle. No such force is being applied to the hovercraft after the thrust fan is shut off.Choice C is incorrect. This arrow indicates the direction of a centripetal force required to keep an object moving in a circle. This would be the force generated by the thrust fan before it is shut off.Choice D is incorrect because a force directed out of the circle would be required to cause the hovercraft to follow this path. No such force exists in this scenario.

• Question 103:

  One distinguishing factor in a redox titration, as opposed to other titrations, is that it involves:

  A. the determining of an unknown concentration in one reactant.
  B. the quantitative analysis of a substance.
  C. the use of a known concentration.
  D. the use of oxidation and reduction.
  D. the use of oxidation and reduction.

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  Explanation/Reference:

  This is the only answer choice that is unique to a redox titration. The other choices are common to various types of titrations.

• Question 104:

  Several models have been developed for relating changes in dissociation constants to changes in the tertiary and quaternary structures of oligomeric proteins. One model suggests that the protein's subunits can exist in either of two distinct conformations, R and T. At equilibrium, there are few R conformation molecules: 10 000 T to 1 R and it is an important feature of the enzyme that this ratio does not change. The substrate is assumed to bind more tightly to the R form than to the T form, which means that binding of the substrate favors the transition from the T conformation to R.

  The conformational transitions of the individual subunits are assumed to be tightly linked, so that if one subunit flips from T to R the others must do the same. The binding of the first molecule of substrate thus promotes the binding of the second and if substrate is added continuously, all of the enzyme will be in the R form and act on the substrate. Because the concerted transition of all of the subunits from T to R or back, preserves the overall symmetry of the protein, this model is called the symmetry model. The model further predicts that allosteric activating enzymes make the R conformation even more reactive with the substrate while allosteric inhibitors react with the T conformation so that most of the enzyme is held back in the T shape. Experiment Evaluating Non-Symmetry Model Enzymes

  Experiments were performed with enzyme conformers that did not obey the symmetry model. The data is summarized in Figure 1.

  

  Figure 1: Equilibrium distribution of two conformers at different temperatures given the free energy of their interconversion. (modified from Mr.Holmium). Allosteric enzymes differ from other enzymes in that they:

  A. are not denatured at high temperatures.
  B. are regulated by compounds which are not their substrates and which do not bind to their active sites.
  C. they operate at an optimum pH of about 2.0.
  D. they are not specific to just one substrate.
  B. are regulated by compounds which are not their substrates and which do not bind to their active sites.

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  Explanation/Reference:

  You must be familiar with how enzyme function is regulated to answer this question. An allosteric enzyme has a site other than the one for the substrate at which a molecule (not the substrate) that directs the function of the enzyme can bind.

  

  The above illustrates the allosteric regulation of an enzyme with a positive effector (on the left) and a negative effector (on the right).

• Question 105:

  Today's new urban Asia is just as sophisticated and in many ways more exciting than Western cities. Urban Asian consumers are knowledgeable, modern, and keen to embrace the global lifestyle. Young, urban Asians have grown up accustomed to many things that originated in the West. They have, for example, completely embraced pizza, some even claiming that it is a part of their heritage. The story is told about a young Singaporean boy who was taken by his father to Rome. "Hey, look, Dad," the little boy exclaimed, "they have pizza here too!" On sampling the product, the boy decided that it was not as good as the original back home. Nury Vitachi, who writes for the South China Post and the Far Eastern Economic Review, describes the Asian middle-class phenomenon: "Executives in Asia have become rich at warp speed by taking full control of their own lives. They invest a great deal of time in their work, they use strategy to scramble up the corporate ladder, and they demand payment in cash -- so they can make their money work as hard as they do." Signs of affluence are everywhere, but don't get carried away. Traveling around Asia, no matter how rich the Asians become, signs of their frugal nature are still apparent. And they are very cost-conscious. Shopkeepers in many Asian cities, most notably in Hong Kong, demand payments for discounted merchandise in cash instead of plastic, and many Asians are accustomed to that. Most people save the increases in their income, and many prefer to put it into fixed or other income-generating assets. Stock, land, and property are their favorites. Many affluent Asians still regard financial security as the most important form of security, and they are confident that Asia is the place to be to achieve that. While many have begun to savor the good life, they are not letting go of their top priority of education for their children. Education is looked upon as the most important contributing factor to success in life. And in many of Asia's competitive urban centers, there is a rush to acquire a second degree and other forms of professional qualification to ensure personal competitiveness in the workplace. There are extraordinary opportunities in Asia for education and training programs from language to software programming. Despite the rise in their assertiveness, Asians still look to the United States and not so much to Europe for ideas and trends. In general, except for those in Hong Kong and Japan, they are not particularly concerned with being fashionable. For today's Asia, Japan and Hong Kong are the sources of Asian fashion ideas, but as Asia becomes more affluent, there is a great opportunity to develop an indigenous fashion industry. For example, a huge market potential exists in introducing new materials and simplified but fashionable designs for countries in tropical Asia with a hot humid climate throughout the year. The population density and lack of space in urban areas has prohibited Asians from exercising frequently and few indulge in outdoor activities. This is changing. Most Asians consider themselves in good health. Compared with Americans, few are overweight -- largely as a result of their Asian diet. But now health clubs are becoming popular among younger Asians. Potential for indoor exercise equipment holds great promise. It is also important to dress for the gym, and younger Asians are serious about looking good, complete with makeup, sunglasses, designer exercise shoes and outfits, and a gym bag. In trying to hit Asia's moving targets, regardless of what you are selling, it is a good idea to stick with market density -- not country by country, but, mostly, city by city. Asian markets can be a marketer's dream in that their densities are among the highest in the world. Java, Indonesia's main island, has 115 million people. On Nanjing Road, Shanghai's busiest street, businesses are open twelve hours a day almost every day of the year. More than 1.5 million people visit the shops there and spend more than $50 million every day. Someone said that you can only become rich if you sell to the rich. I would add that you can become rich faster if you sell to the new rich. For investors in the West, watch for Western companies that are preparing a big push in Asia. The world has not yet seen anything like it before, and you can reap handsome dividends if you back those stocks that are going eastward.

  It can be inferred from the passage that:

  A. the Asian fashion market is already saturated with indigenous designs and manufacturers.
  B. credit cards are gaining acceptance slowly as a form of payment for merchandise in Asia.
  C. the comparative lack of space in urban Asia has led to increased health problems.
  D. competitive professionals often pursue additional education and training.
  D. competitive professionals often pursue additional education and training.

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  Explanation/Reference:

  It is stated in paragraph four that there is a rush to enhance personal competitiveness through further education and training.

  Choice A is negated in the fifth paragraph, which states that great opportunities exist in developing an indigenous fashion industry. Choice B is incorrect. Nothing in the passage hints at an increased acceptance of the credit card as a method

  of payment. In fact, in paragraph three, the author gives an example in which the notion of paying by credit card is still meeting resistance. Choice C is incorrect. Paragraph six discusses the increased congestion but does not judge its impact

  on public health. The author even implies that opportunities for outdoor activities are not as important in Asia as they are in America because of the healthfulness of the Asian diet.

• Question 106:

  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.

  What technique was being used by researchers from the Asian grocery store program if they tried to recruit more participants by asking for referrals to those who had previously agreed?

  A. Random digit dialing
  B. Snowball sampling
  C. Purposive sampling
  D. Simple random sampling
  B. Snowball sampling

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  Explanation/Reference:

  B is correct. Snowball sampling is a non-probabilistic sampling technique that involves asking research subjects to refer or recommend people from their social network who might be interested in participating. The idea is that over time, the "snowball" gets larger. A major limitation of this type of sampling strategy is the amount of sampling bias introduced into the study. Specifically, study participants may lack diversity A. This is incorrect. Random digit dialing is a probabilistic sampling strategy that randomly selects phone numbers within area codes to recruit participants. C. This is incorrect. Purposive sampling is a non- probabilistic sampling strategy that looks for certain characteristics and only selects those who fulfil selection criteria. D. This is incorrect. Simple random sampling is a probabilistic sampling technique that will typically use a number generator to select subjects for a study.

• Question 107:

  The reaction below is NOT spontaneous at any temperature.

  2ICl(g) I2(g) + Cl2(g)

  Which of the following is true?

  

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

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  Explanation/Reference:

  The relationship between G , H, S, and temperature is G = H ?TS For a reaction to be spontaneous, G must be less than zero. If a reaction is not spontaneous at any temperature, H must be positive and S must be negative. No matter what the temperature, G will always be positive and the reaction will be nonspontaneous. Choice B is therefore the correct response. Choice A is for a reaction that would be spontaneous if the temperature was sufficiently high. Choice C is for a reaction that is spontaneous at ALL temperatures. Choice D is for a reaction that would be spontaneous if the temperature was sufficiently low.

• Question 108:

  What is the term for the temperature at which a material loses its permanent magnetism?

  A. the Bose temperature
  B. the Weiss temperature
  C. the Boyle temperature
  D. the Curie temperature
  D. the Curie temperature

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  Explanation/Reference:

  This is also known as the Curie point.

• Question 109:

  What is the wavelength of the light in millimeter?

  A. 5.4 x 10-3
  B. 5.4 x 10-5
  C. 5.4 x 10-4
  D. 5.4 x 10-10
  C. 5.4 x 10-4

• Question 110:

  Aski jump is an inclined track from which a ski jumper takes off through the air. After traveling down the track, the skier takes off from a ramp at the bottom of the track. The skier lands farther down on the slope.

  Figure 1 shows a ski jump, in which the ramp at the lower end of the track makes an angle of 30° to the horizontal. The track is inclined at an angle of to the horizontal and the slope is inclined at an angle of 45° to the horizontal. A ski jumper is stationary at the top of the track. Once the skier pushes off, she accelerates down the track, and then takes off from the ramp. The vertical height difference between the top of the track and its lowest point is 50 m, and the vertical height difference between the top of the ramp and its lowest point is 10 m.

  

  Figure 1

  The distance traveled by the skier between leaving the ski jump ramp and making contact with the slope is called the jump distance. In some cases, in order to increase the jump distance a skier will jump slightly upon leaving the ramp,

  thereby increasing the vertical velocity. Unless otherwise stated, assume that friction between the skis and the slope is negligible, and ignore the effects of air resistance.

  Another ski jumper sets off from a point farther down the jump track, and leaves the ramp at a speed of 16 m/s. If the time in flight is 4 s, what is the total horizontal distance traveled by the ski jumper after leaving the ramp?

  

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

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  Explanation/Reference:

  In this question we are told that the ski jumper leaves the jump slope at a speed of 16 m/s, and that she remains in flight for a time of 4 seconds. Using this information, we need to find the horizontal distance traveled. Now in the horizontal direction, there are no forces acting on the ski jumper; so the horizontal distance traveled is equal to the horizontal speed times the total time in flight. We know the total time in flight, but don't have a value for the horizontal velocity. However,

  

  we do have the total velocity, and we know the angle at which she leaves the jump slope. So we can use the equation , where Vn is the horizontal component of velocity, Vt is the total velocity, and is the angle measured

  

  with respect to the horizontal. Substituting in known values, we get that the horizontal velocity Vn = 16 cos 30? which equals 16 , or 8 m/s. Using this we can calculate the horizontal distance traveled, and we get that the horizontal distance

  

  traveled equals meters, choice C.