Maintains an electrical gradient that is the basis for excitability in nerve and muscle cells. Where is the cell more negative? Inside or out? Inside! This is important for propogation of signals in neurons
Export of sodium from the cell provides the driving force for several facilitated
transporters, which import glucose, amino acids and other nutrients into the cell.
Creates an osmostic gradient that drives absorption of water. Examples are found in small intestine and in the kidney.