Osmosis Experiment

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Osmosis Experiment

Aim: To investigate the factors which affect osmosis in potatoes and

to investigate one in detail.

Introduction: Osmosis is the net movement of water from a high

concentration to a low concentration through a semi permeable

membrane. This diagram demonstrates it.

In plants osmosis takes place between the cytoplasm and the solution

outside of the cell. The effects of osmosis on the plant cell are

visible to the eye. When a plant cell is placed in a less concentrated

sugar solution the water passes through the cell wall, cell membrane

and cytoplasm and into the central vacuole. The increased pressure in

the central vacuole pushes out on the walls of the cell which gives

the cell rigidity. When the plant cell is in this state it is known as

being turgid.

Sometimes plants cells can be placed in more concentrated sugar

solutions, although

this is unlikely in nature. If this happens the water passes out

through the central vacuole,

through the cytoplasm, the cell membrane and the cell wall into the

solution outside

the cell. This causes the pressure inside the central vacuole to

decrease. The cell looks

visibly deflated and limp. This state is known as plasmolysed.

The solution which has a higher osmotic pressure is known as being

hypotonic. If the cell is turgid the solution inside the central

vacuole is hypotonic, if a cell is plasmolysed the solution outside

the cell is hypotonic. There is also a stage where the concentrations

of solution inside and outside the cell are equal. This is known as an

isotonic state.

Factors: There are many factors which could affect osmosis in

potatoes, they are:

· The size of the potato- a larger potato would have a larger surface

area which would mean more cells are closely exposed to the sugar


· The type of the potato may have an effect on the rate of osmosis.

· Concentration of the solution - the greater the difference in
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