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Sample MCAT Questions: Biological Sciences

BIOLOGICAL SCIENCES
24 QUESTIONS
35 MINUTES

DIRECTIONS:

 

The following questions or incomplete statements are in groups. Preceding each series of questions or statements is a paragraph or a short explanatory statement, a formula or set of formulas, or a definition. Read the written material and then answer the questions or complete the statements. Select the ONE BEST ANSWER for each question and indicate your selection by marking the corresponding letter of your choice on the Answer Form. Eliminate those alternatives you know to be incorrect and then select an answer from among the remaining alternatives.

 

 

Passage I (Questions 64-66)

 

As the left ventricle of the heart contracts, it generates a pressure, which when more than that in the aorta causes the ejection of a volume of blood. The action of the ventricle can be represented as therelationship between the volume of blood in the ventricle and the intraventricularpressure. The relationship between ventricular pressure and volume is knownas the Frank-Starling law of the heart.

During systole, the ventricle contracts, but no bloodis ejected until the pressure in the ventricle exceeds the pressure in theaorta. This phase of the cardiac cycle is known as isovolumetric contraction.When the aortic valve opens, blood is ejected without further increase inthe ventricular pressure. Therefore, this phase of contraction is isotonicand results in the ejection of a volume of blood known as the stroke volume.

When the pressure that the ventricle can generate exactly equals the aortic pressure, the ejection of blood ceases; and the ventricle undergoes isovolumetric relaxation. The blood from the atrium then fillsthe ventricle, and the pressure increase is the result of passive resistanceof the ventricle.

 64. Assuming a constant mean aortic pressure, patients with renal failure may have an increased blood volume which results in an increased end diastolic volume in the ventricle. What effect does this increase have on cardiac function?

  I. ventricular work remains constant

II. stroke volume increases

III. end systolic volume increases

IV. ventricular work increases

  A. I, II, and III only                    C. II and IV only

B. I and III only                        D. IV only
 
 

 65. Patients with hypertension have a higher mean aorticpressure. If end diastolic volume stays constant:

 

I. stroke volume increases.

II. ventricular work increases.

III. end systolic volume decreases.

IV. ventricular work may or may not increase.

 

A. I, II, and III only                           C. II and IV only

B. I and III only                                 D. IV only
 

66. With a constant mean aortic pressure and as compared to normal, a compensated failure will show:
 

 I. an increase in stroke volume.
II. a stroke volume which may or may not decrease.
III. a decrease in cardiac work.
IV.  an increase in end systolic volume. A.  I, II, and III only                            C. II and IV only
B.I and III only                                    D. IV only
 

 

Passage II (Questions 67-73)

In a laboratory experiment, red blood cells were placed into 0.5 M solutions and the appearance of the solutions was observed two hours later with the naked eye.

 

Solution Cells

0.5 M glucose no change

0.5 M sucrose no change

0.5 M urea hemolysis of RBCs

0.5 M glycerol hemolysis of RBCs

 

 67. How can the solutions of urea and glycerol be described with respect to the red blood cells?

A. isotonic                                    C. hypertonic

B. hypotonic                                 D. none of the above

 68. The reason for these results is that:

  I. the number of particles in the urea and glycerolsolutions is greater than that in the glucose and sucrose solutions.

II. glucose and sucrose form coatings around the red blood cells, which prevent their breaking.

III. glucose and sucrose enter the cells but are immediately metabolized, therefore water does not enter the cells.

IV. urea and glycerol can enter the cell, water follows them into the cell because it is then in greater concentration outside.

 

A. I and II only         C III and IV only

                               B. I and III only        D. IV only


69. The property of the cell membrane that allows for this phenomenon to be demonstrated is called:
A. diffusion.                                C. impermeability.

B. osmosis.                                 D. semipermeability.

 70. The process by which a cell can move a substance from a point of lower concentration to a point of higher concentration (against the diffusion gradient) is called:

A. osmosis               C. turgor pressure
B plasmolysis.          D. active transport.
 

71. Which of the following structures are NOT considered modifications of the cell membrane?

   A. basement membrane

B. terminal bars

C. desmosomes

D. intercalated discs


72. The plasma membrane of animal cells:

  
A. is usually rigid.
B. has selective channels made of proteins
C. is too thin to be seen by the use of any microscope.
D. is composed only of proteins and carbohydrates.   73. Dialysis (as is used for the treatment of chronic kidney ailments) differs from the process of osmosis in the respect that:

 

A. both solvent and solute pass through the membrane.

B. solute selectively passes through the membrane only.

C. solvent selectively passes through the membrane only.

D. gases are the only substances that pass the membrane and blood is cleansed.

 

 

 Passage III (Questions 74-78)

 

Enzymes have often been referred to as biological catalysts. They have many properties in common with other catalysts.

74. Enzymes are generally:

 

           A. carbohydrates         C. lipids. B. proteins                             D. nucleic acids
 

75. Enzymes function in reactions by:

 A.  increasing the net energy yield.
 B.  raising the energy level of the products.
C. decreasing the energy of activation.
D. changing the thermodynamic nature of a reaction, thusmaking a reaction thermodynamically favorable when it would not otherwisebe so.

   76. The nature of enzymes requires that the enzyme is:

 

A. used up in quantities greater than those of substrate that is converted to product.

B. used up in quantities approximately equal to thoseof substrate that is converted to product.

C. used up in quantities significantly less than those of the substrate that is converted to product.

D. essentially not used up and must be rePlacedonly in small quantities.

 

 77. Activity of enzymes is often regulated by covalent modification. This is most often accomplished by:

 

A. phosphorylation/dephosphorylation.

B. sulfation/desulfation.

C. substitution of one cation for another.

D. substitution of one anion for another.

 

 78. The response of most enzymes to being boiled in an aqueous solution is:

 

A. substantially increased activity.

B. substantially decreased activity.

C. an increase of about 1 unit in isoelectric point.

D. no noticeable change is detected.

 

 Passage IV (Questions 79-83)

All of the possible ketopentose sugar isomers have been synthesized in a research project. The ketopentose isomers have then been reduced with sodium borohydride, converting the ketone function to an alcohol.

 

79. The total number of 2-ketopentose isomers is:

A. two.                                       C. six.

. B. four.                          D. eight.

 

80. The total number of isomers of the sugar alcohols produced by sodium borohydride reaction is: A. two.                                      C. four.

B. three.                                    D. five.

 

81. If all the sugar alcohols in the previous question were selectively oxidized so that the number 3 hydroxyl was converted toa ketone, there would be __________ chiral center(s) in each molecule. A. one                                          C. three

B. two                              D. four

 82. The pentose(s) found in RNA usually consists of:

A. deoxyribose.                                    C. various pentoses.

B. ribose.                                              D. glucose.

 83. If the sugar alcohols in question 80 were oxidized to convert carbon numbers 1 and 5 to carboxyls, the number of chiral centers would be:

A. none.                                             C. two.

B. one.                                               D. three.
 

Passage V (Questions 84-87)

The synthesis of proteins and nucleic acids is seen as being directed by a series of coded messages. The messages must be sent,received, and decoded.

 

  84. The primary source or repository of information concerning synthesis of nucleic acids and proteins is considered to be:
                                              A. protein.                         C. RNA.

                                              B. DNA.                            D. peptides.


85. In the polymer that directs protein biosynthesis, there is a requirement of unit(s)

(or monomers) to code for each amino acid.

A. one                             C. three
B. two                              D. four


86. In a chromosome of higher animals there is(are) strand(s) of DNA.

A. one C. three

B. two D. four

 

87. Ultimately, synthesis of protein requires:

A.   DNA.                      C. protein.
B.RNA.                         D. all of the above.

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