The membrane potential in a particular hyperpolarized cell is measured to be -70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is presented. Indicate whether each channel is driven to pass the ion into (I) or out of (O) the cell. Your answer would be a four-letter string composed of letters I and O only, e.g. IIII.
( ) K? channel; the K? equilibrium potential is -60 mV.
( ) Na? channel; the Na? equilibrium potential is +70 mV.
( ) Ca²? channel; the Ca²? equilibrium potential is +130 mV.
( ) Cl- channel; the Cl- equilibrium potential is -90 mV.

Question

The membrane potential in a particular hyperpolarized cell is measured to be -70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is presented. Indicate whether each channel is driven to pass the ion into (I) or out of (O) the cell. Your answer would be a four-letter string composed of letters I and O only, e.g. IIII.
( )	K? channel; the K? equilibrium potential is -60 mV.
( )	Na? channel; the Na? equilibrium potential is +70 mV.
( )	Ca²? channel; the Ca²? equilibrium potential is +130 mV.
( )	Cl- channel; the Cl- equilibrium potential is -90 mV.

Quizplus · Accepted Answer

The driving force for the transport of these ions comes from the electrochemical gradient across the membrane; that is, the membrane potential minus the Nernst potential for each ion-the ion is transported in the direction that would dissipate this gradient. For example, in this particular cell, the positively charged potassium ions tend to enter the cytoplasm to change the membrane potential from -70 mV to the more positive value of -60 mV.

The Membrane Potential in a Particular Hyperpolarized Cell Is Measured