| Osmosis is the movement of water particles across a semi-permeable membrane (partially permeable membrane PPM) from an area of high water concentration to an area of low water concentration. |
Cell membranes are partially permeable because they will only permit some things to pass through, but not others. The reason for this is that PPM has extremely small pores in it. They are so small that only water particles can pass through them, and larger particle like glucose and proteins can not.
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Experiment to demonstrate osmosis! You can demonstrate this effect with VISKING TUBING, which is partially permeable membrane. It is sometimes called dialysis tubing as it is used in kidney dialysis machines. |
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From the animation it can be seen that water level in the glass tube begins to rise or fall because water either enters or leaves through the visking tubing by osmosis. |
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Remember: Potato Slices | ||||||||||
| It can be seen from the animation
that potato slices, in pure water, swell up as water
enters their cells by osmosis.
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However, in concentrated sugar solution the potato slices shrink as water leaves their cells as a result of osmosis. |
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