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Diffusion

Particles (molecules and ions) in a liquid and a gas move continuously. Because of this movement, particles will spread themselves evenly throughout a liquid or a gas.

If there is a situation where particles of a substance are in a higher concentration, they will move from this region to where they are in a lower concentration. This is called .

It is important to remember that the particles:

  • will move in both directions, but there will be a movement from high to low concentration
  • will end up evenly spread throughout the liquid or gas, but will continue to move

Some examples of diffusion in biological systems

Some substances move into and out of living cells by diffusion.

In a leaf

Diagram showing the process of diffusion in a leaf

In the lungs

Diffusion in the lungs. Oxygen diffuses from high concentration in alveolus to low concentration in blood. Carbon dioxide diffuses from high concentration in blood to low concentration in alveolus.

Liver cells

Some examples of diffusion in biological systems