What contributes significantly to membrane potential in cells?

The Na-K-ATPase pump plays a pivotal role in establishing and maintaining the membrane potential in cells. This pump actively transports sodium ions out of the cell and potassium ions into the cell against their concentration gradients, using ATP as an energy source. By moving three sodium ions out for every two potassium ions brought in, the pump creates a net negative charge inside the cell relative to the outside.

This activity not only helps maintain concentration gradients essential for various cellular functions but also contributes to the electrical gradient, which is critical for processes such as action potential generation in neurons and muscle cells. The continuous operation of the Na-K-ATPase pump is fundamental to sustaining the resting membrane potential, typically around -70mV in neurons.

In summary, the Na-K-ATPase pump's function as an active transport mechanism is crucial for establishing the electrochemical gradients that dictate membrane potential, making it a significant contributor to this essential physiological characteristic.