B4 -Key points

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Defination - The movement of a substance from an area of high concentraion to an area of low concentration

Diffusion works becuase particle are always moving about in a random way. The rate of diffusion can be increased in a number of ways:

  • A smaller distance
  • A greater surface area
  • A bigger concentration    


Defination - Osmosis is the movement of water across partially permeale membrane from an area of high water concentration to an area of low water concentration.

The cell membrane is an example of a partially permeable membrane. It lets small molecues though - such as water. It stops larger molecules - such as glucose.

When plant cells gain water by osmosis, they swell The cell wal stops them from bursting. This makes the cell stiff or…


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