What is active transport ?
Active transport is the mediated transport of biochemical and other atomic/molecular substances across cell and nuclear membranes.
It's called active transport because it requires chemical energy (in the form of ATP).
In this form of transport, the molecules move in a direction opposite against their electrical gradient or concentration gradient.
What does the sodium-potassium pump do?
This is an enzyme that is located in the cell membrane of animal cells and pumps sodium ions out of the cell (into the extracellular fluid) and potassium ions into the cell (coming from the extracellular fluid).
This costs energy in the form of ATP, as both ions are pumped against their electrochemical gradient.
The sodium-potassium pump ensures that the sodium concentration in the cell is lower than outside, and the potassium concentration higher.
This will create a concentration difference.
Sodium channels and potassium channels can then generate an action potential to transmit signals or to put the cell to work.
The sodium-potassium pump, in each step, exchanges three sodium ions ( coming from the inside of the cell and going to the extracellular fluid) for two potassium ions (from outside of the cell to the inside of the cell) so that on balance one elemental charge leaves the cell.
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