Physiology Quiz -
The Membrane Potential - Part 4
Cells of multicellular organisms such as animals and plants, as well as those of unicellular organisms such as yeast exhibit a potential difference across the cell plasma membrane. That is to say that there is an electrical potential difference between the inside of the cell and the surrounding bathing medium of the cell. This potential difference is referred to as the membrane potential (Vm). The numerical value of the membrane potential is generally negative, meaning that the inside of the cell is negative with respect to the outside solution, which is taken as the reference or zero value.

Test your knowledge of the membrane potential by taking this series of quizzes. For more information about the membrane potential, see the Resting Membrane Potential lecture notes.
(1)   Assuming resting physiological cytoplasmic and extracellular concentrations of Na+ (see here), determine the Na+ equilibrium potential (VNa).
 (A)   0 mV (B)   +61 mV (C)   −61 mV (D)   +96 mV (E)   −96 mV
(2)   Assuming resting physiological cytoplasmic and extracellular concentrations of K+ (see here), determine the K+ equilibrium potential (VK).
 (A)   0 mV (B)   +61 mV (C)   −61 mV (D)   +96 mV (E)   −96 mV
(3)   Assuming resting physiological cytoplasmic and extracellular concentrations of Cl (see here), determine the Cl equilibrium potential (VCl).
 (A)   0 mV (B)   +64 mV (C)   −64 mV (D)   +96 mV (E)   −96 mV
(4)   Assuming resting physiological cytoplasmic and extracellular concentrations of Ca2+ (see here), determine the Ca2+ equilibrium potential (VCa).
 (A)   0 mV (B)   +137 mV (C)   −137 mV (D)   +274 mV (E)   −274 mV
(5)   Assume that in a cell at rest, only K+ channels are open in the plasma membrane. This situation could arise if all other ion channels are blocked by the addition of pharmacological agents (i.e., blockers or inhibitors). Under this condition, what is the value of the membrane potential (Vm) in this cell?
 (A)   The membrane potential is the same as the equilibrium potential for K+ (Vm = VK). (B)   The membrane potential is the same as the equilibrium potential for Na+ (Vm = VNa). (C)   The membrane potential is the same as the equilibrium potential for Cl− (Vm = VCl). (D)   None of the above is correct. (E)   All of the above are possible.
(6)   Assume that in a cell at rest, only Na+ channels are open in the plasma membrane. This situation could arise if all other ion channels are blocked by the addition of pharmacological agents (i.e., blockers or inhibitors). Under this condition, what is the value of the membrane potential (Vm) in this cell?
 (A)   The membrane potential is the same as the equilibrium potential for K+ (Vm = VK). (B)   The membrane potential is the same as the equilibrium potential for Na+ (Vm = VNa). (C)   The membrane potential is the same as the equilibrium potential for Cl− (Vm = VCl). (D)   None of the above is correct. (E)   All of the above are possible.
(7)   Assume that in a cell at rest, only Cl channels are open in the plasma membrane. This situation could arise if all other ion channels are blocked by the addition of pharmacological agents (i.e., blockers or inhibitors). Under this condition, what is the value of the membrane potential (Vm) in this cell?
 (A)   The membrane potential is the same as the equilibrium potential for K+ (Vm = VK). (B)   The membrane potential is the same as the equilibrium potential for Na+ (Vm = VNa). (C)   The membrane potential is the same as the equilibrium potential for Cl− (Vm = VCl). (D)   None of the above is correct. (E)   All of the above are possible.

Posted: Thursday, August 14, 2014
Last updated: Thursday, August 14, 2014