Transport in Cells: Osmosis and Active Transport

This lesson covers osmosis and active transport as required by AQA GCSE Biology specification 4.1.3. You need to understand the process of osmosis, how to investigate it experimentally, the effects of osmosis on plant and animal cells, and how active transport differs from diffusion and osmosis.

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What Is Osmosis?

Osmosis is the movement of water molecules from a region of higher water concentration (a dilute solution) to a region of lower water concentration (a more concentrated solution) through a partially permeable membrane.

Osmosis is a special case of diffusion — it specifically describes the movement of water molecules only, and it always involves a partially permeable membrane.

Key Definitions