osmosis

• Osmosis is the diffusion of water molecules from a high water concentration to a low water concentration across a partially permeable membrane
• Dilute solutions have a high concentration of water molecules
• Concentrated solutions have a low concentration of water molecules
• Turgid cell - when water enters the vacuole of a cell and it pushes against the cell wall, increasing turgor pressure within the cell
• Flaccid cell - when water moves out of the plant cell vacuole, causing the cell to become soft
• If a lot of water leaves the cell, the cytoplasm starts to peel away from the cell wall. This is called plasmolysis.
• When animal cells swell up and burst due to the gain of water, this is called lysis
• When animal cells shrink due to the loss of water, this is called crenation
• If an animal cell is put in pure water, it becomes turgid then bursts
• If an animal cell is put in a concentrated solution, it loses water by osmosis until it is shrunken or haemolysed
• Hypertonic - when there is a higher water concentration outside a cell than inside
• Isotonic - when there is an equal water concentration outside and inside a cell
• Hypotonic - when there is a lower concentration outside a cell than inside
• A plasmolysed cell is hypertonic
• A flaccid cell is isotonic
• A turgid cell is hypotonic
• In a hypertonic solution, animal cells shrink and plant cell vacuoles shrink
• In an isotonic solution, animal and plant cells remain the same
• In a hypotonic solution, animal cells become turgid then burst, while plant cell vacuoles expand, causing the cell to become turgid