Wednesday, September 14, 2011

Sodium Potassium Pump

The sodium-potassium pump is an active transport protein (ATPase) which is located in the plasmatic membrane of cells. It pumps three sodium ions (Na+) out of the cell, and two potassium ions (K+) into the cytoplasma of the cell. The sodium-potassium pump works with the interference of ATP (adenosine triphosphate), which phosphorylates the pump and change its shape, making it possible the release of the three Na+ out of the cell and into the extra cellurar space (outside the cell). Once the sodium-potassium pump has changed its shape, letting the three Na+ out, it immediately binds two K+ from outside the cell; this change the pump back to its original shape, absorving the two K+ into the cell.

Thus, for each ATP that is broken down, the pump moves 3 sodium ions out and 2 potassium ions in. When the cell is depleted of sodium, it creates an electrical gradient and a concentration gradient, both of which are put to use for many tasks. Nevertheless, the resting membrane potential is mosly decided by the permeability of the membrane to K and Na. The permeability through "leaky channels" for K is around 75 more times more permeable than Na. Therefore, The electric gradient is established when K goes down its concentration gradient, causing more positive charge outside of the cell. The Na/K pump only contributes to 20% of resting membrane potential.

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.

Sodium-Potassium Pump (Video)