B4 - Diffusion

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If someone let's off a stink bomb at the end of the corridor why does everyone smell it? It's called diffusion. The smelly gaseous particles spread out in to all the spaces available.

Diffusion (definition):

- movement of a substance from a region of high concentration to a region of low concentration.

Diffusion helps substances get in and out of cells.

Diffusion and cells

All living things are made out of cells. In plants the contents are surrounded by a cell membrane and cell wall. Substances such as oxygen and carbon dioxide pass through these by diffusion.

It passes through by the:

 - outer cell wall which is completely permeable to many molecules

 - the cell membrane which is partially - permeable

Diffusion and the leaf

Plants use up carbon dioxide during photosynthesis. And because of this the concentration of carbon dioxide is low during photosynthesis. The higher concentration of carbon dioxide…


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