<P> Export of sodium from the cell provides the driving force for several secondary active transporters membrane transport proteins, which import glucose, amino acids, and other nutrients into the cell by use of the sodium gradient . </P> <P> Another important task of the Na - K pump is to provide a Na gradient that is used by certain carrier processes . In the gut, for example, sodium is transported out of the reabsorbing cell on the blood (interstitial fluid) side via the Na - K pump, whereas, on the reabsorbing (lumenal) side, the Na - glucose symporter uses the created Na gradient as a source of energy to import both Na and glucose, which is far more efficient than simple diffusion . Similar processes are located in the renal tubular system . </P> <P> Failure of the Na - K pumps can result in swelling of the cell . A cell's osmolarity is the sum of the concentrations of the various ion species and many proteins and other organic compounds inside the cell . When this is higher than the osmolarity outside of the cell, water flows into the cell through osmosis . This can cause the cell to swell up and lyse . The Na - K pump helps to maintain the right concentrations of ions . Furthermore, when the cell begins to swell, this automatically activates the Na - K pump . </P> <P> Within the last decade, many independent labs have demonstrated that, in addition to the classical ion transporting, this membrane protein can also relay extracellular ouabain - binding signalling into the cell through regulation of protein tyrosine phosphorylation . The downstream signals through ouabain - triggered protein phosphorylation events include activation of the mitogen - activated protein kinase (MAPK) signal cascades, mitochondrial reactive oxygen species (ROS) production, as well as activation of phospholipase C (PLC) and inositol triphosphate (IP3) receptor (IP3R) in different intracellular compartments . </P>

Why is the sodium potassium pump called an electrogenic pump