Sample battle · revision
Training Camp · Mission Brief
Biology · Cell Transport
Cells move substances across their membrane to stay alive. Some methods need energy (active), others don't (passive). Direction and energy cost depend on concentration gradients and molecule size.
Key terms
- Diffusion — Passive movement of particles from high to low concentration.
- Osmosis — Passive movement of water across a semi-permeable membrane.
- Active transport — ATP-powered movement against a concentration gradient.
Memory trick: OWL — Osmosis = Water Loves moving down its gradient.
Common mistake: Osmosis is not 'water moving from low to high water concentration' — it's high water to low water (i.e. low solute to high solute).
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