Comparing Osmosis in Plants & Animals (Cambridge (CIE) AS Biology): Revision Note
Exam code: 9700
Osmosis in cells: comparison
| Plant cells | Animal cells |
|---|---|---|
Cell membrane | Present Composed of a phospholipid bilayer Selectively permeable | |
Cell wall | Present Composed of cellulose Fully permeable | Absent |
Osmosis of water into and out of cell | Can occur | |
Cell placed in solution with a lower water potential | Water leaves through the selectively permeable cell surface membrane by osmosis Volume of the cell decreases Protoplast shrinks / pulls away from the cell wall Cell is plasmolysed | Water leaves the cell through the selectively permeable cell surface membrane by osmosis Volume of cell decreases Cell shrinks / shrivels up |
Cell placed in solution with a higher water potential | Water enters the cell through the selectively permeable cell surface membrane by osmosis Volume of cell increases Protoplast expands / pushes against the cell wall The cell wall withstands the increased pressure created The pressure increases until the cell is rigid and firm (turgid) The cell is fully inflated with water and no more can enter | Water enters the cell through the selectively permeable cell surface membrane by osmosis Volume of cell increases There is no cell wall to resist the increased pressure that is created The cell membrane is eventually overstretched and the cell bursts |
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