TYPES OF OSMOTIC SOLUTIONS
A) Hypotonic Solutions (hypo - low solute)
A hypotonic solution contains a lower solute concentration than the solution in the cell. Therefore the solution must also have a high solvent (water) concentration as compared to the cell.
solute
100% H2O
0% solute 80% H2O
Outside the Cell 20% solute
Inside the Cell
H2O
Therefore the direction of osmosis is into the cell because
[H2O]outside is greater than the [H2O] inside.
The pressure produced by the movement of water into the cell is call osmotic pressure.
Effects on Animal Cells Effects on Plant Cells
As the animal cell gains water by osmosis, As the plant cell gains water by osmosis. the cell membrane is being stretched and if Water will enter and fill the central vacuole, swelling continues the cell will undergo which will push on the cytoplasm and the cell cytolysis (lyse) and cause the cell to burst. wall. This internal pressure is called turgor pressure. The increase pressure causes the Therefore animal cells need to remove excess cell to swell. The cell wall prevents the cell water. from rupturing. In this condition the cell is said to be turgid. This is an ideal state for plants. B) Hypertonic Solutions (hyper - high solute) ______0898e0b3f3333d651c4eca90345ef319.doc A hypertonic solution contains a high solute concentration than the solution in the cell. Therefore the solution must also have a low solvent (water) concentration as compared to the cell.
solute
90% H2O
10% solute 99% H2O
Outside the Cell 1% solute
Inside the Cell
H2O
Therefore the direction of osmosis is out of the cell because
[H2O]outside is less than the [H2O] inside.
Effects on Animal Cells Effects on Plant Cells
An animal cell will lose water by osmosis. As the plant cell loses water by osmosis, the The cell will shrivel or crenate. central vacuole will shrink causing the turgor pressure to drop. The cell membrane will A cell can conserve water by pumping out salt come away from the cell wall causing the cell (solute). to be less rigid. This condition is called plasmolysis. i.e. Bony fish in sea water If the cell reaches this state it will be lethal and the cell may not recover.
C) Isotonic Solutions
______0898e0b3f3333d651c4eca90345ef319.doc An isotonic solution contains an equal solute concentration as the one found inside the cell.
solute
75% H2O
25% solute 75% H2O
Outside the Cell 25% solute
Inside the Cell
H2O
Therefore rate of osmosis into the cell is equal to the rate of osmosis out of the cell because
[H2O]outside is equal to [H2O] inside.
Therefore the net movement of molecules is zero.
Effects on Animal Cells Effects on Plant Cells
The volume of the animal cell remains Since there is no net movement of water unchanged since there is a dynamic across the membrane of the cell, the size of equilibrium across the cell membrane. the cell remains the same. The cell membrane is just touching the cell wall.
The plant cell has become flaccid (limp) and therefore the plant cell will lose some of its structural support do to low turgor pressure.
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