During the repolarization phase of an action potential, the potassium ions diffuse out of the cell, and active transport begins.
What I do not understand is why active transport is needed when the movement of ions is not against their concentration gradient?
Since the potassium ions have diffused out in repolarization, only the sodium ions are left in the intracellular space.
The sodium/potassium pump is used to pump 3 sodium ions out and 2 potassium ions in. However, isn't there a concentration gradient as the sodium ions are moving out of the cell, where there are no sodium ions, and thus from a high concentration to a low concentration?
Is it because the active transport allows the imbalance to occur (3 out and 2 in)?