AEMCA Practice Exam

How does the sodium-potassium pump operate?

1. Pumps 2 potassium to the extracellular space for every 3 sodium intracellularly

2. Pumps 3 sodium to the intracellular space for every 2 potassium extracellularly

3. Pumps 3 sodium to the extracellular space for every 2 potassium intracellularly

4. Transfers sodium and potassium equally without preference

The correct answer is: Pumps 3 sodium to the extracellular space for every 2 potassium intracellularly

The sodium-potassium pump operates through a mechanism that is crucial for maintaining the electrochemical gradients across the plasma membrane of cells. It actively transports sodium ions out of the cell and potassium ions into the cell, which is essential for various cellular functions, including maintaining cell potential, regulating cell volume, and facilitating nutrient absorption. The correct understanding of the pump's operation is that it typically transports three sodium ions out of the cell and two potassium ions into the cell. This means that for every cycle of the pump, a net movement of positive charge occurs out of the cell, contributing to the resting membrane potential. This specific arrangement of movement is vital for the proper functioning of many physiological processes. It establishes a concentration gradient, where sodium is more concentrated outside the cell, and potassium is more concentrated inside. Additionally, the pump's action is critical for other transport systems, as it helps maintain the necessary gradients for secondary active transport mechanisms. Other options do not accurately represent the mechanism of the sodium-potassium pump. The key aspect of option C aligns with the established physiological knowledge about the pump's role and function.