What is the combined effect of concentration gradient and membrane potential on ion movement called?

The combined effect of concentration gradient and membrane potential on ion movement is referred to as the electrochemical gradient. This term encompasses both the concentration gradient, which is the difference in the concentration of ions across the membrane, and the voltage difference, or membrane potential, which affects how ions move in response to electric fields.

When considering ion movement in biological systems, ions naturally diffuse from an area of higher concentration to an area of lower concentration, which is driven by the concentration gradient. Simultaneously, the membrane potential influences ion movement, as positively charged ions will tend to move toward more negative areas and vice versa for negatively charged ions. The interplay of these two forces determines the overall direction and magnitude of ion flow across membranes, making the electrochemical gradient a crucial concept in cellular biology and physiology.