English: This diagram shows the resting membrane potential of a cell membrane and the movement of ions across it. Sodium ions are concentrated outside the cell, while potassium ions and negatively charged proteins are more concentrated inside the cell. These unequal ion distributions create a resting membrane potential of approximately -70 mV, making the inside of the cell negatively charged relative to the outside. Depending on the cell, membrane potential can range from -20 to -200 mV.