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Osmosis Investigation

Satisfactory Essays
Osmosis Investigation

Osmosis is a “type of diffusion where water passes through a

semi-permeable membrane from where water is in high concentration to a

low concentration.”

A French scientist (Jean-Antoine Nollett) discovered osmosis in 1748.

He discovered it by filling a pig’s bladder with alcohol. This was

then placed in water for several hours. The water had moved into the

pig’s bladder but very little alcohol had moved out. The pig’s bladder

was a semi-permeable membrane.

The particles in a liquid are constantly moving. When small particles

or water molecules meet a semi-permeable membrane they may pass

through. But larger particles, like glucose cannot get through the

membrane at all. If there is a high concentration of water molecules

on one side of the membrane, then water molecules will pass through

the membrane and the water appears to have moved through the membrane

to the lower concentration.

If the concentrations on both sides of the membrane are equal, then

there will be no movement of water. This is the Isotonic Point. In

this way we can find the concentration of cytoplasm. If the

concentration of a sugar solution that caused no osmosis to occur was

found, then the concentrations of both the sugar solution and the

cytoplasm must be equal.

This process happens in both plant and animal cells. Plants have a

strong cellulose wall surrounding them. So they gain water through

the roots by osmosis and move water into the plant cells using

osmosis. This is how plants become turgid or stiff, which helps keep

them upright. Then the pressure of the cell will rise so that no more

water can enter the cell. This is called “Hydrostatic pressure” it

works against osmosis. But when plants are faced with a low

concentrated water solution (sucrose) the will lose water and become

flaccid. Which is the opposite of turgid. So the plant cell will

shrink instead of grow. When a plant is placed in an equal

concentration solution between water and sugar then the plant will be
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