Cells maintain a low intracellular Na+ concentration and a high intracellular K+ concentration by sodium-potassium pump which is an example of:

Some carriers transpo substances against their electrical and chemical gradients. This form of transpo requires energy and is called active transpo. In animal cells, the energy is provided almost exclusively by hydrolysis of ATP. One of these ATPases is sodium-potassium adenosine triphosphatase (Na, K ATPase), which is also known as the Na, K pump. Na, K ATPase catalyzes the hydrolysis of ATP to adenosine diphosphate (ADP) and uses the energy to extrude three Na+ from the cell and take two K+ into the cell for each molecule of ATP hydrolyzed. It is an electrogenic pump in that it moves three positive charges out of the cell for each two that it moves in, and it is therefore said to have a coupling ratio of 3:2. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 2. Overview of Cellular Physiology in Medical Physiology. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.