MCAT Sample Questions

Biochemistry

In order to become active, a Map kinase has to undergo phosphorylation of its catalytic domain on amino acids 183 and 185 according to the primary structure. To create a catalytically inactive Map kinase – a kinase dead mutant – the most likely substitution within its active domain would be:

  • A. A183T185.
  • B. Y183A185.
  • C. G183A185.
  • D. S183Y185.

Biology

The human kidney can be damaged from a number of causes resulting in a patient’s inability to filter toxins (i.e. urea) from the body which could result in death. Complete kidney failure is usually first treated with dialysis which “cleans” the blood.

Figure 1: Dialysis. The “dialyzer” is a glass container that has 3 main components: (1) blood percolating through to be cleaned; (2) a dividing membrane; and (3) the dialysate. The latter is liquid containing chemicals used to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream. (kidney.niddk.nih.gov)

Considering the information provided, which of the following is NOT consistent with the process of dialysis?

  • A. The membrane in the dialyzer separating the dialysate and the blood must be semipermeable.
  • B. The concentration of toxins in the dialysate must increase during dialysis.
  • C. The concentration of glucose and vital minerals in the dialysate must be similar to that of the patient’s blood.
  • D. Excessive minerals and toxins cross the membrane in the dialyzer by osmosis.

Biology/Biochemistry

Apoptosis is the process of programmed cell death that can occur in multicellular organisms. The proteins involved in apoptosis are associated with pathways for cell cycle arrest and DNA repair. These processes are mostly regulated through the interplay of various proteins involved in feedback loops including some of the ones shown in Figure 1.

Figure 1: Feedback loops forming a regulatory network affecting apoptosis, cell cycle arrest and DNA repair. (Bioformatics Institute)

According to Figure 1, CDK2 activity would most reasonably increase due to all of the following EXCEPT:

  • A. degradation of p21.
  • B. high cyclin G concentrations.
  • C. a mutation in the gene that produces PTEN.
  • D. high p53 concentrations.

 

The red bread mold Neurospora crassa grows well on a cultural plate with “minimal” medium which is a fluid containing only a few simple sugars, inorganic salts, and vitamin. Neurospora that grows normally in nature (wild type) has enzymes that convert these simple substances into the amino acids necessary for growth. Mutating any one of the genes that makes an enzyme can produce a Neurospora strain that cannot grow on minimal medium. The mutant would only grow if the enzyme product were to be added as a supplement. On the other hand, if a “complete” medium is provided, containing all required amino acids, then Neurospora would grow, with or without mutation.

 

Figure 1: A synthesis pathway for the amino acid arginine. Each gene in italics in the diagram produces one enzyme necessary for the synthesis of this essential amino acid required for growth.

Table 1: Growth response of mutant strains in “minimal” media with supplements as indicated. Growth is indicated by (+), and no growth is indicated by (-).

Question 2

According to the information provided, a conclusion that can be made with certainty is that neither mutant strain P nor Q have the defective enzyme:

  • A. carbamoyltransferase.
  • B. argininosuccinate synthase.
  • C. argininosuccinase.
  • D. None of the above enzymes are defective in either mutant strain P nor Q.

Question 3

Experiments using the two mutant strains P and Q, reveal that strain P accumulates citrulline, but strain Q does not. Which of the following statements is most consistent with the data provided?

  • A. Strain Q has only one mutation.
  • B. Strain P has a mutation in argF only.
  • C. Strain P has mutations in argF, argG and argH.
  • D. Strain P has a mutation in argG only.

Physics

Electron Beam Therapy (EBT) is a form of radiotherapy where electrons are directed to a tumor site. Consider an electron moving at constant velocity which enters the area between two charged plates, as shown in the diagram below. Which of the paths correctly indicates the electron’s trajectory after leaving the area between the charged plates?

  •  A.  A
  •  B.  B
  •  C.  C
  •  D.  D

General Chemistry

Which of the following energy sublevels can contain the most electrons?

  •  A.  n = 4, l = 0
  •  B.  n = 5, l = 2
  •  C.  n = 6, l = 2, ml = +1
  •  D.  n = 4, l = 3

Psychology 

Drinking a cup of coffee is something people do every day, alone or with friends, at home or at work. A researcher following the theory of symbolic interactionism who is observing two people enjoying a coffee together would primarily point out that:

  • A. The symbolic value of coffee is that the drinking ritual is more important than the drink itself.
  • B. Coffee is a stimulant drug.
  • C. Coffee is the second most valuable commodity in international trade.
  • D. Coffee is a branded and politicized consumption good.

Sociology

If the goal of the health communication is to have influence on individuals, families, neighborhoods, medical and social service organizations, and ultimately public health policy, they are adhering to:

  • A. Ecological theory.
  • B. Family systems theory.
  • C. John Bowlby’s attachment theory.
  • D. Milton Gordon’s assimilation theory.