Animal cells have a membrane that separates the interior of the cell from the outside environment. Typically, an electric potential difference exists between the inner and outer surfaces of the membrane. Consider one such cell where the magnitude of the potential difference is 50 mV, and the inner surface of the membrane is at a higher potential than the outer surface. A sodium ion (Na+) is initially just outside the cell membrane (initially at rest). How much work (in J) is required for a cell to absorb the ion, so that it moves from the exterior of the cell to the interior? X Note that a positive charge is moving from a lower to a higher potential. What does this mean about change in potential energy of the system? For this to occur, does energy exit the system, or does energy need to be supplied? How is electric potential energy related to electric potential? Be careful with units. J