Question

At equilibrium potential for potassium:

a) The NA+/K+ pump is pumping out of the cell?

b) Leak channels for potassium are closed?

c) There is no current measured ?

d) There an un-equal amounts of potassium ions moving across the membrane depending on the concentration difference?

e) There is no potassium ions moving across the membrane?

Answer 1

Option A-is correct.

At equilibrium potential for potassium---Na+-K+ still pumps 3 Na+ out for 2 K+ inside

In a resting membrane--There is More K+ inside the cell than Outside the cell--So potassium moves out of the channles along its concentration gradient.Also Na+-K+ pump pumps 3 Na+ out for 2 K+ inside the cell.As more potassium leaks down through the K+ Channels--the concentration of Potassium inside the cells decreases.

At a Membrane potential of about -90mV---there will be equilibrium potential for K+.

At equilibrium potential for K+

The concentration gradient of K+ is balanced eventhough there is some electrical potential difference across the membrane.

Here eventhough K+ ions still cross the membrane via Leak channels, there is no net movement of K+ across the membrane.

Option B is incorrect-Potassium still leaks through leak channels

Option C is incorrect-Since there is a net voltage of -90mV there is current .

Option D is incorrect-There is equall amount of K+ moving in and out of the cell---But there is no net movement.

Option E-Incorrect-Eventhough there is no Net movement of K+ ----There is movement of K+ across membrane