The pump maintaining sodium and potassium balance across the cell membrane?

• A. Sodium-Glucose Cotransporter
• B. Potassium Channel
• C. Sodium-Potassium Pump
• D. Sodium-Calcium Exchanger

Answer: (C)

This question tests how cells keep sodium and potassium levels balanced across the cell membrane. The sodium-potassium pump is the primary mechanism for this, actively moving ions against their gradients using energy from ATP. It exports three sodium ions out of the cell and brings two potassium ions in with each ATP molecule hydrolyzed, creating and maintaining the essential gradients that support resting membrane potential and cellular homeostasis. These gradients underpin electrical excitability, volume regulation, and many transport processes. Other mechanisms either allow ions to move passively down their gradients (such as a potassium channel), use the sodium gradient for secondary transport like glucose uptake, or exchange ions to influence calcium handling (such as a sodium-calcium exchanger). But only the sodium-potassium pump directly maintains the sodium and potassium balance across the membrane.