Comparing Osmosis in Plants & Animals | CIE AS Biology Revision Notes 2025

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