Biological implications of osmosis
Tonicity describes the relative solute concentration of a cell and its surroundings.
There are three types of tonicity:
- A hypotonic solution has a low solute concentration relative to the cell. When a cell is in a hypotonic solution, water will enter.
- A hypertonic solution has a high solute concentration relative to the cell. When a cell is in a hypertonic solution, water will leave.
- Isotonic solutions have the same concentration as the cell. There is no net movement of water in or out of the cell.
An animal cell will burst when in a hypotonic solution. Plant cells will not burst, because they are protected by cell walls. Instead, they become turgid (stiff).
Stems of non-woody plants can stand upright due to turgidity.
Animal cells shrivel and become flaccid (loose) in hypertonic solutions. Plant cells first become flaccid and then undergo plasmolysis. Plasmolysis is the shrinking of the cytoplasm away from the cell wall.