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Sodium-potassium pump
 
To support vital functions cell needs an intense exchange of various compounds with extracellular medium. One way for the exchange is a passive transportation when the compounds enter into the cell due to gradients of concentration (like oxygen, carbon dioxide, glucose) or by osmosis (water). In addition there are mechanisms of the compounds or ions transportation against gradient. This kind of transfer needs energy support and it is called active transportation. Special proteins called pumps are responsible for such kind of exchange. This model represents a functioning of the pump that provides transportation of sodium and potassium ions through cellular membrane. Intracellular part of the protein hydrolyzes molecules of ATP and utilizes the released energy to support the active ion transportation. Two ions of potassium enter the cell instead of three ions of sodium released. This is a mechanism that provides high concentration of potassium ions inside of cell (35 times higher than in extracellular media) and low concentration of sodium ions (14 times lower than outside the cell). These ratios provide a support of electrical potentials on the membranes, a stimulation of nervous and muscle cells, regular functioning of some other intracellular processes. The model is initiated by the "Start" button. The "Stop" button interrupts the animation, while the "Reset" button returns it into initial state.
 
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