The sodium-potassium pump actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, both against their concentration gradients, using ATP as its energy source.
Here's a breakdown of the process:
-
Binding of Sodium Ions: The pump protein (Na+/K+ -ATPase) initially binds three sodium ions (Na+) from the intracellular fluid.
-
ATP Hydrolysis: Simultaneously, ATP (adenosine triphosphate) binds to the pump. The pump then hydrolyzes ATP, breaking it down into ADP (adenosine diphosphate) and a phosphate group. The phosphate group remains attached to the pump.
-
Conformational Change: The attachment of the phosphate group causes the pump to change its shape (undergo a conformational change).
-
Release of Sodium Ions: This shape change causes the sodium ions to be released into the extracellular fluid.
-
Binding of Potassium Ions: The new shape of the pump now has a high affinity for two potassium ions (K+) from the extracellular fluid, which bind to the pump.
-
Dephosphorylation: The binding of potassium ions triggers the release of the phosphate group from the pump.
-
Return to Original Conformation: The loss of the phosphate group causes the pump to revert to its original shape.
-
Release of Potassium Ions: This shape change causes the potassium ions to be released into the intracellular fluid. The pump is now ready to bind sodium ions again, and the cycle repeats.
In summary, the sodium-potassium pump uses the energy from ATP hydrolysis to actively transport 3 Na+ ions out of the cell and 2 K+ ions into the cell, maintaining the electrochemical gradient necessary for nerve impulse transmission, muscle contraction, and other vital cellular functions.
