Ionic Potentials across Cell Membranes Conceptual Question In its resting state,

Question

Ionic Potentials across Cell Membranes Conceptual Question In its resting state, the membrane surrounding a neuron is permeable to potassium ions but only slightly permeable to sodium ions. Thus, positive K ions can flow through the membrane in an attempt to equalize K concentration, but Na ions cannot as quickly. This leads to an excess of Na ions outside of the cell. If the space outside the cell is defined as zero electric potential, then the electric potential of the interior of the cell is negative. This resting potential is typically about -80 mV. A schematic of this situation is shown in the figure. During the resting phase, what is the electrical potential energy of a typical K ion inside of the cell? -40 meV +40 meV -80 meV +80 meV 0 meV Part C During depolarization, what is the work done (by the electric field) on the first few Na ions that enter the cell? - 40 meV +40 meV -80 meV +80 meV -120 meV +120 meV 0 meV

Explanation / Answer

Solution:

B)

As we know;

there's no electric potential outside of the cell membrane.
=> U=qV=eV

=> U = eV = -80 meV

C)

just to conquer the potential difference

i.e;

negative of the above

=> +80meV

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