Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!

Did you know?

We also have Bitesize study guides covering many subjects at National 4 and National 5 on our Knowledge & Learning BETA website.

Home > Biology > Revision videos > Cells and diffusion


Cells and diffusion


Osmosis is the net movement of water from a high water concentration to a low water concentration across a membrane. In this video osmosis is explained with the help of a large net and a crowd of human volunteers.

In order to see this content you need to have both Javascript enabled and Flash installed.


Key points

  • Cell membranes are selectively permeable.
  • Water is able to move across membranes by the process of osmosis.
  • Osmosis is the net movement of water from an area of high concentration to an area of low concentration through a selectively permeable membrane.
  • Plants use osmosis to take up water into their roots and this makes the cells firm or turgid.
  • Animal cells have no cell wall and so there is a danger they will burst if they take in too much water.
  • Animal cells shrivel up if they lose too much water.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.