Final answer:
When the membrane is permeable to several different ions, the Goldman-Hodgkin-Katz voltage equation is used to calculate diffusion potential. It factors in the permeabilities and concentrations of ions that can cross the membrane.
Step-by-step explanation:
The equation used for diffusion potential when the membrane is permeable to several different ions is known as the Goldman-Hodgkin-Katz voltage equation or just the Goldman equation. The voltage across a cell membrane in its resting state arises because the membrane is semipermeable, allowing certain ions to pass while blocking others. In typical mammalian cells, the membrane is permeable to K+ (potassium) and Cl- (chloride) ions but impermeable to Na+ (sodium) ions. As ions diffuse down their concentration gradient, a charge separation occurs, establishing a membrane potential. The Goldman equation takes into account the permeability and concentration of each ion that can cross the membrane, providing a way to calculate the resulting potential difference.