MCAT Biochemistry Practice Test 3: Nonenzymatic Protein Function and Protein Analysis

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1. At what pH can protein A best be obtained through electrophoresis? (Note: MM = molar mass)

ProteinpIMM
Protein A4.525,000
Protein B6.010,000
Protein C9.512,000
  • A. 2.5
  • B. 3.5
  • C. 4.5
  • D. 5.5

2. What is the function of sodium dodecyl sulfate (SDS) in SDS-PAGE?

  • A. SDS stabilizes the gel matrix, improving resolution during electrophoresis.
  • B. SDS solubilizes proteins to give them uniformly negative charges, so the separation is based purely on size.
  • C. SDS raises the pH of the gel, separating multiunit proteins into individual subunits.
  • D. SDS solubilizes proteins to give them uniformly positive charges, so separation is based purely on pH.

3. Which of the following is NOT involved in cell migration?

  • A. Dynein
  • B. Flagella
  • C. Actin
  • D. Centrioles

4. Which of the following proteins is most likely to be found extracellularly?

  • A. Tubulin
  • B. Myosin
  • C. Collagen
  • D. Actin

5. Hormones are found in the body in very low concentrations, but tend to have a strong effect. What type of receptor are hormones most likely to act on?

I. Ligand-gated ion channels

II. Enzyme-linked receptors

III. G protein-coupled receptors

  • A. I only
  • B. III only
  • C. II and III only
  • D. I, II, and III

6. Which of the following is most likely to be found bound to a protein in the body?

  • A. Sodium
  • B. Potassium
  • C. Chloride
  • D. Calcium

7. Which of the following characteristics is NOT attributed to antibodies?

  • A. Antibodies bind to more than one distinct antigen.
  • B. Antibodies label antigens for targeting by other immune cells.
  • C. Antibodies can cause agglutination by interaction with antigen.
  • D. Antibodies have two heavy chains and two light chains.

8. Which ion channels are responsible for maintaining the resting membrane potential?

  • A. Ungated channels
  • B. Voltage-gated channels
  • C. Ligand-gated channels
  • D. No ion channels are involved in maintenance of the resting membrane potential.

9. Which of the following is NOT a component of all trimeric G proteins?

  • A. Gα
  • B. Gβ
  • C. Gγ
  • D. Gi

10. Which of the following methods would be best to separate large quantities of the following proteins? (Note: MM = molar mass)

ProteinpIMM
Protein A6.528,000
Protein B6.370,000
Protein C6.6200,000
  • A. Ion-exchange chromatography
  • B. Size-exclusion chromatography
  • C. Isoelectric focusing
  • D. Native PAGE

11. Which amino acids contribute most significantly to the pI of a protein?

I. Lysine

II. Glycine

III. Arginine

  • A. I only
  • B. I and II only
  • C. I and III only
  • D. II and III only

12. How does the gel for isoelectric focusing differ from the gel for traditional electrophoresis?

  • A. Isoelectric focusing uses a gel with much larger pore sizes to allow for complete migration.
  • B. Isoelectric focusing uses a gel with SDS added to encourage a uniform negative charge.
  • C. Isoelectric focusing uses a gel with a pH gradient that encourages a variable charge.
  • D. The gel is unchanged in isoelectric focusing; the protein mixture is treated before loading.

13. Which protein properties allow UV spectroscopy to be used as a method of determining concentration?

  • A. Proteins have partially planar characteristics in peptide bonds.
  • B. Globular proteins cause scattering of light.
  • C. Proteins contain aromatic groups in certain amino acids.
  • D. All organic macromolecules can be assessed with UV spectroscopy.

14. A protein collected through affinity chromatography displays no activity even though it is found to have a high concentration using the Bradford protein assay. What best explains these findings?

  • A. The Bradford reagent was prepared incorrectly.
  • B. The active site is occupied by free ligand.
  • C. The protein is bound to the column.
  • D. The protein does not catalyze the reaction of interest.

15. What property of protein-digesting enzymes allows for a sequence to be determined without fully degrading the protein?

  • A. Selectivity
  • B. Sensitivity
  • C. Turnover
  • D. Inhibition