Sodium-Potassium Pump Notes

Sodium-Potassium Pump

The sodium-potassium pump is a well-known ATPase pump.
Prevalent in the majority of cells, including all muscle and neuron cells.
Important in the kidneys for reabsorption; pumps sodium, and water follows, along with other substances.
Uses the most energy in the body.

Initial State: The pump is open to the inside of the cell.
Sodium Binding: Three sodium ions (Na^+) bind to the pump.
ATP Hydrolysis:
- Binding of sodium ions triggers the conversion of ATP to ADP.
- The released phosphate group attaches to the pump.
Conformational Change 1: Phosphorylation induces a conformational change, opening the pump to the outside of the cell.
Sodium Release: The three sodium ions are released outside the cell.
Potassium Binding: Two potassium ions (K^+) bind to the pump.
Phosphate Release: Binding of potassium ions triggers the release of the phosphate group.
Conformational Change 2: Dephosphorylation induces another conformational change, opening the pump to the inside of the cell.
Potassium Release: The two potassium ions are released inside the cell, and the pump returns to its initial state.
Cycle Repeats: The pump is now open to the inside, ready to bind three sodium ions and repeat the cycle.

The sodium-potassium pump re-establishes the concentration gradients for sodium and potassium.
- High sodium concentration outside the cell.
- High potassium concentration inside the cell.
These concentration gradients are used by regular ion channels or ion carriers to move ions along their concentration gradients via facilitated diffusion.
The pump moves three sodium ions out of the cell for every two potassium ions it moves in.