# Goldman equation

**Goldman equation** is an equation used to calculate the electrical equilibium potential across the cell's membrane in the presence of more than one ions taking into account the selectivity of membrane's permeability. It is derived from the Nernst equation.

## Equation

The Goldman equation can be expressed as follows:

or

where

E_{m} is the potential difference of an ion between membranes

R is the universal gas constant; R = 8.314471 J mol-1

T is the thermodynamics temperature, in Kelvin; 0 K = -273.15oC

z is the number of moles of electrons transferred between membranes (defined by the valency of ion)

F is the Faraday's constant; F = 96,485.3415 C mol-1

P_{A or B }is the permeability of the membrane to a particular ion (A or B)

[A or B]_{o} is the concentration of ion outside the membrane

[A or B]_{i} is the concentration of ion inside the membrane

## See also

## References