The potential difference that is observed to exist between the fluid inside a living cell and the surrounding fluid is maintained by an electrical double layer on the cell membrane. The potential diff...The potential difference that is observed to exist between the fluid inside a living cell and the surrounding fluid is maintained by an electrical double layer on the cell membrane. The potential difference that is observed at the electrodes of a battery is the difference between the electrode potentials of two dissimilar conductors immersed in an electrolyte.