If a solution of pure water has the highest water potential possible. A red blood cell is placed into this solution of pure water. The red blood cell has a much lower water potential than the pure water. Which way will the water move and why? And what will happen to the cell?
Water moves from the region of higher water potential to the region of lower water potential. Thus, in this case water will move into the cell. The volume of the red blood cell will be gradually increasing. The cell will swallow, and it may even burst.