Animation of plasmolysis
This animation shows how water passes by osmosis out of a plant cell placed in a concentrated solution (lower water content than cytoplasm). The vacuole reduces in size and disappears, and the cytoplasm shrinks away from the side of the cell wall. Eventually the cell contents become a ball of cytoplasm with a central nucleus, resembling an animal cell inside the outline of a plant cell wall. The cell membrane (red in this animation) can now be seen - it was previously pushed against the cell wall.
The cell membrane is differentially permeable (allowing water to pass through), and the more substantial cell wall is completely permeable to water and solutes.
