MCAT Biochemistry Practice Test 8: Biological Membranes

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1. A student is trying to determine the type of membrane transport occurring in a cell. She finds that the molecule to be transported is very large and polar, and when transported across the membrane, no energy is required. Which of the following is the most likely mechanism of transport?

  • A. Active transport
  • B. Simple diffusion
  • C. Facilitated diffusion
  • D. Exocytosis

2. A researcher treats a solution containing animal cells with ouabain, a poisonous substance that interferes with the sodium–potassium ATPase embedded in the cell membrane, and the cell lyses as a result. Which of the following statements best describes ouabain's effects?

  • A. Treatment with ouabain results in high levels of extracellular calcium.
  • B. Treatment with ouabain results in high levels of extracellular potassium and sodium.
  • C. Treatment with ouabain increases intracellular concentrations of sodium.
  • D. Treatment with ouabain decreases intracellular concentrations of sodium.

3. Resting membrane potential depends on:

I. the differential distribution of ions across the membrane.

II. active transport processes.

III. selective permeability of the phospholipid bilayer.

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

4. Which of the following is NOT a function of the cell membrane?

  • A. Cytoskeletal attachment
  • B. Protein synthesis
  • C. Transport regulation
  • D. Second messenger reservoir

5. The dynamic properties of molecules in the cell membrane are most rapid in:

  • A. phospholipids moving within the plane of the membrane.
  • B. phospholipids moving between the planes of the membrane.
  • C. proteins moving within the plane of the membrane.
  • D. proteins exiting the cell through exocytosis.

6. Which lipid type is LEAST likely to contribute to membrane fluidity?

  • A. Unsaturated glycerophospholipids
  • B. trans glycerophospholipids
  • C. Cholesterol
  • D. Unsaturated sphingolipids

7. A membrane receptor is most likely to be a(n):

  • A. embedded protein with catalytic activity.
  • B. transmembrane protein with sequestration activity.
  • C. membrane-associated protein with sequestration activity.
  • D. transmembrane protein with catalytic activity.

8. Which of the following is NOT a cell–cell junction in animals?

  • A. Desmosomes
  • B. Gap junctions
  • C. Plasmodesmata
  • D. Tight junctions

9. Which of the following is true of diffusion and osmosis?

  • A. Diffusion and osmosis rely on the electrochemical gradient of only the compound of interest.
  • B. Diffusion and osmosis rely on the electrochemical gradient of all compounds in a cell.
  • C. Diffusion and osmosis will proceed in the same direction if there is only one solute.
  • D. Diffusion and osmosis cannot occur simultaneously.

10. The bulk movement of liquid into a cell through vesicular infoldings is known as:

  • A. phagocytosis.
  • B. pinocytosis.
  • C. exocytosis.
  • D. drinking.

11. Which of the following is LEAST likely to be the resting membrane potential of a cell?

  • A. –70 mV
  • B. –55 mV
  • C. 0 mV
  • D. +35 mV

12. How does the inner mitochondrial membrane differ from the outer mitochondrial membrane?

  • A. The inner mitochondrial membrane is more permeable and lacks cholesterol.
  • B. The inner mitochondrial membrane is less permeable and lacks cholesterol.
  • C. The inner mitochondrial membrane is more permeable and has cholesterol.
  • D. The inner mitochondrial membrane is less permeable and has cholesterol.

13. For most cells, the extracellular calcium concentration is around 10,000 times higher than the intracellular calcium concentration. What is the membrane potential established by this electrochemical gradient?

  • A. –123 mV
  • B. –61.5 mV
  • C. +61.5 mV
  • D. +123 mV

14. Which of the following statements conflicts with the fluid mosaic model?

  • A. The cell membrane is static in structure.
  • B. Membrane components can be derived from multiple biomolecules.
  • C. Hydrophobic interactions stabilize the lipid bilayer.
  • D. Proteins are asymmetrically distributed within the cell membrane.

15. Which of the following is a sphingolipid?

  • A. Lecithin
  • B. Phosphatidylinositol
  • C. Cholesterol
  • D. Gangliosides