Investigating Osmosis in Potatoes

Investigating Osmosis in Potatoes

Aim:

Investigate the movement of osmosis through a selectively permeable

membrane, in this case potato.

Introduction:

Osmosis is the movement of water through a semi permeable membrane.

The water passes from an area of high concentration to an area of low

concentration, until the two concentrations are equal in

concentrations of water.

Many cell membranes behave as semi permeable membranes, and osmosis is

a vital part in the movement of liquids in living organisms, for

example, in the transport of water from the soil to the roots in

plants.

If a cell is in contact with a solution of lower water concentration

than its own contents, then water leaves the cell by osmosis, through

the cell membrane. And if the cell is in contact with a solution of

high water concentration than its own then water goes into the cell.

If you put a plant cell in water, water enters by Osmosis, then it

swells up. However, the cell will not burst. This is because the cell

walls are made from something which is extremely strong. Eventually,

the cell stops swelling, and when this happens, we say the cell is

turgid. This is important, because it makes plant stems strong and

upright.

Osmosis:

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Preliminary Work:

For my preliminary work, I used 30mm of potato. To begin, I used 25mls

of Sucrose solution. The first thing I needed to see was how different

concentrations affected the weight and length of the potato. So I

needed to see each extreme - highest concentration and lowest

concentration. I used 0 molar concentrations (the lowest) and 1 molar

(the highest.)

I then left each test for 20 minutes, but found after that time a

slight reaction had taken place - the potato chips only increased or

decreased by a very short amount. I then predicted that now I would

have to leave the tests for a longer amount of time and use longer

potato chips to ensure that there is enough of a reaction to compare