CAIE IGCSE Biology 3.1.1 Diffusion

Practise recognising and defining diffusion from particle movement, gas exchange and membrane examples in plants, animals and air.

Exam points

state diffusion as net particle movement down a concentration gradient
link oxygen or carbon dioxide movement to higher and lower concentration regions
select diffusion, rather than osmosis or active transport, for gas or scent movement

[Maximum number: 2]

Fig. 1.1 shows the movement of particles through an epithelial cell in the small intestine.

Fig. 1.1

In Fig. 1.1, arrow P represents the diffusion of oxygen molecules.

Describe what is meant by the term diffusion.

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