Water in cells should be maintained in narrow range of concentration for optimal function.
What happens if water concentration of a cell increases beyond the range?
If we put a cell in a hypotonic solution... (Solution with less salt concentration).
Osmosis is the net movement of water molecules from a region of high concentration to a region of their low concentration through a selectively permeable membrane.
Therefore water molecules move from external watery environment to the cell. This is known as endosmosis.
If a plant cell has lower water potential than the narrow range, water molecules move towards the cell until the concentration of cell reaches the narrow range. Therefore the cell will absorb water until it reaches the maximum volume. Rigid cell wall controls the volume of cell. This state is known as turgid.
If animal cell has lower water potential than its limit the cell will absorb water from external environment.
Animal cells do not have cell wall. Therefore there is no limitation for absorption of water. Cell will burst when their volume exceed than maximum level. This can be seen if we place a red blood cell (erythrocyte) in distilled water on a microscopic slide and observe under the microscope. Red blood cell soon begins to inflate and burst like an inflated balloon.
What happens if water concentration in cell decreases below its range?
If we put a cell in a hypertonic solution... (Solution with high salt concentration), the cell starts to shrink due to water in cell moves out side the cell. This is known as exosmosis.
In Plant cell the cytoplasm is attached with cell wall due to shrinkage the cytoplasm will shrink and detached from the cell. This shrinkage is known as plasmolysis. Eventually cell will die due to loss of water.