Discuss the Working of Sodium–Potassium Pump
The sodium–potassium pump (Na⁺/K⁺-ATPase) is a vital membrane-bound enzyme that actively transports sodium (Na⁺) and potassium (K⁺) ions across the plasma membrane, maintaining cellular electrochemical gradients. This process requires energy derived from ATP hydrolysis, making it an example of primary active transport.
Mechanism of Action
- The pump is an antiporter that transports 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell per ATP molecule consumed.
- Initially, the pump binds three intracellular Na⁺ ions.
- ATP is hydrolyzed, and the pump is phosphorylated, leading to a conformational change that expels Na⁺ ions to the extracellular space.
- In this phosphorylated state, the pump binds two extracellular K⁺ ions.
- Dephosphorylation of the pump returns it to its original conformation, releasing K⁺ ions inside the cell.
Significance
- Resting Membrane Potential: Maintains the negative membrane potential in neurons and muscle cells.
- Osmotic Balance: Prevents cell swelling by regulating ion concentration and osmotic pressure.
- Electrochemical Gradient: Provides the driving force for secondary active transport (e.g., glucose and amino acid uptake).
Clinical Importance
Inhibition of the sodium-potassium pump by cardiac glycosides like digoxin increases intracellular Ca²⁺ levels, enhancing cardiac contractility. Malfunctioning pumps can lead to cellular dysfunction, hypertension, and neurological problems.
Overall, the sodium–potassium pump is essential for cellular homeostasis, signal transmission, and physiological processes such as muscle contraction and nerve impulse conduction.