Membrane potential Knowledge-Based Download PDF

Questions

1. 1.

   How does an increase in the extracellular concentration of potassium ions ($\text{K}^+$) affect the resting membrane potential of an animal cell?

   • A) It causes the resting membrane potential to become more negative because potassium efflux is accelerated.
   • B) It has no effect on the resting membrane potential because the resting membrane is completely impermeable to potassium ions.
   • C) It causes the resting membrane potential to become less negative because the concentration gradient driving potassium efflux is reduced.
   • D) It hyperpolarizes the membrane because the sodium-potassium pump immediately stops transporting ions across the lipid bilayer.
2. 2.

   Which statement best describes the condition under which a specific permeant ion reaches its electrochemical equilibrium across a biological membrane?

   • A) The intracellular and extracellular concentrations of the ion become identical.
   • B) Active transport mechanisms responsible for moving the ion shut down completely.
   • C) The plasma membrane becomes completely impermeable to any movement of that ion.
   • D) The electrical gradient across the membrane exerts a force that is equal in magnitude and opposite in direction to the chemical concentration gradient.
3. 3.

   Why is the resting membrane potential of a typical animal cell significantly closer to the equilibrium potential of potassium than to that of sodium?

   • A) The resting membrane has a substantially higher permeability to potassium ions than to sodium ions.
   • B) The sodium-potassium pump actively imports three potassium ions for every two sodium ions extruded.
   • C) Negatively charged intracellular proteins specifically attract sodium ions out into the extracellular fluid.
   • D) The concentration gradient of sodium ions across the plasma membrane is completely dissipated at rest.
4. 4.

   If the plasma membrane of a resting animal cell suddenly becomes significantly more permeable to sodium ions ($\text{Na}^+$), what immediate change in membrane potential occurs?

   • A) The membrane hyperpolarizes because sodium ions move outward down their concentration gradient.
   • B) The membrane potential remains completely stable because active transport prevents passive sodium influx.
   • C) The membrane depolarizes as sodium ions enter the cell down their electrochemical gradient.
   • D) The membrane potential shifts to zero because intracellular anions rapidly exit alongside sodium ions.
5. 5.

   Which of the following primarily establishes and maintains the resting membrane potential in animal cells?

   • A) Rapid influx of calcium ions through ligand-gated channels
   • B) Free diffusion of negatively charged intracellular proteins across the lipid bilayer
   • C) Active transport of ions by the sodium-potassium pump combined with potassium leak channel permeability
   • D) Complete impermeability of the plasma membrane to all positively charged inorganic cations