cce education system

A pump is a protein that hydrolyses ATP in order to transport a particular solute through a membrane in order to generate an electrochemical gradient to confer certain membrane potential characteristics on it. This gradient is of interest as an indicator of the state of the cell through parameters such as the Nernst potential. In terms of membrane transport the gradient is of interest as it contributes to increased system entropy in the co-transport of substances against their gradient. One of the most important pumps in animal cells is the sodium potassium pump, that operates through the following mechanism:[7] binding of three Na+ ions to their active sites on the pump which are bound to ATP.
ATP is hydrolyzed leading to phosphorylation of the cytoplasmic side of the pump, this induces a structure change in the protein. The phosphorylation is caused by the transfer of the terminal group of ATP to a residue of aspartate in the transport protein and the subsequent release of ADP. the structure change in the pump exposes the Na+ to the exterior. The phosphorylated form of the pump has a low affinity for Na+ ions so they are released. once the Na+ ions are liberated, the pump binds two molecules of K+ to their respective bonding sites on the extracellular face of the transport protein.This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell.
The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released into the cytosol. ATP binds, and the process starts again.