The biologically necessary concentration gradient between a number of different ions must constantly be maintained by active, energy-consuming transport mechanisms (ion pumps).
Living cells spend a large part of their energy on these pumps (ca. 30 % for a typical mammalian cell). The transport, which naturally runs opposite to the concentration gradient, is relatively slow (ca. 400 - 500 ions per second).
For comparison, ion chanels can transport up to 107 ions per second.
The transport is coupled to an overall charge transport through the membrane and to the consumption of ATP (ATPase !!).
The transporter, whose molecular structure is not yet fully known, is a glycoprotein. Its conformation is changed by the coordination of K+ and Na+ ions and/or by phosphorylation. Ions are permanently transported through the membrane by this process.