Cell Biology IGCSE
IGCSE (Year 10โ11) ๐ฌ Cell Biology & Biochemistry Detailed cell structure, osmosis, diffusion, active transport.
๐ฌ Osmosis
Osmosis is the movement of water molecules from a region of higher water potential to a region of lower water potential across a selectively permeable membrane.
| Condition | Animal cell | Plant cell |
|---|---|---|
| Placed in distilled water (hypotonic) | Water enters โ cell swells and bursts (lysis) | Water enters โ cell becomes turgid (wall prevents bursting) |
| Same concentration (isotonic) | No net movement โ cell unchanged | No net movement โ flaccid |
| Concentrated solution (hypertonic) | Water exits โ cell shrinks (crenation) | Water exits โ plasmolysis (membrane pulls away from cell wall) |
๐ฌ Diffusion vs Active Transport
| Process | Direction | Energy (ATP)? | Membrane proteins? | Examples |
|---|---|---|---|---|
| Diffusion | High โ low conc. | No | Not required | Oโ, COโ in alveoli |
| Osmosis | High ฯ โ low ฯ (water) | No | Aquaporins | Water into root cells |
| Facilitated diffusion | High โ low conc. (via proteins) | No | Carrier/channel proteins | Glucose into cells |
| Active transport | Low โ high (against gradient) | Yes | Carrier proteins (ATPase) | Mineral ions into roots, glucose reabsorption in kidney |
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Interactive Demo โ Cell Biology IGCSE
Adjust concentration to see osmosis.
Osmosis & Water Potential Calculator
M = I / A and water potential calculations.