How does ATP deficiency cause cell swelling?
The cell volume depends on the proper functioning of the plasma membrane, which remains semipermeable only if properly energized with ATP. ATP provides fuel for the Na/K ATPase, which acts as a pump, keeping the high concentration of sodium in the intercellular fluid and the high concentration of potassium inside the cell. If this ATPase malfunctions because of an energy deficiency, an uncontrolled influx of sodium and water from the extracellular space occurs. A consequent net increase of the total fluid content in the cytoplasm results in cell swelling. The intracellular concentration of potassium declines because potassium leaks out of the cell.