Investigation osmosis in potato cells

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                Muhammad Kermali 10k

                Biology Coursework

Investigating Osmosis in potato cells

Aim:

To investigate the effect of varying the concentration of sucrose solutions and to see if osmosis occurs in potato cells.

Research/definition:

Osmosis is the diffusion of a solvent through a semi permeable membrane from a region of low solute concentration to a region of high solute concentration. The semi permeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion.

Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become turgid when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid pressure works against osmosis. Turgidity is very important to plants because this is what make the green parts of the plant stand up into the sunlight.

Prediction:

I think that the lower the concentration of sugar in the water, the more mass the potato chip will gain after the experiment is finished.  This is because the water potential in the potato will be lower than the water potential in the solution, and therefore, osmosis will occur, resulting in water being ‘absorbed’ by the potato.

I also think that if the concentration of sucrose in the water is high, the potato will then have a higher water potential than the solution, which will result in water dispersing away from the potato and into the solution, causing the potato to lose mass.

In my experiment, there may be a concentration of the solution which has an equal water potential to the potato, which will result in neither a gain nor a loss of mass for the potato chip as the water would have no preference of location.

Plant vacuoles accumulate enough dissolved compounds to give the plant cell a low enough osmotic potential to absorb water via osmosis.

Preliminary test:

List of apparatus:

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Planned/detailed method:

A range of sucrose solutions will be prepared with concentrations 0.2 molar, 0.4 molar, 0.6 molar, 0.8 molar and 1 molar. This will be done by adding varying amounts of distilled water to varying amounts of sugar solution. Sections of potato will be cut using a scalpel and will be measured using a ruler. The chips should also be weighed and dried before the experiment begins. This part of the preparation must be done very accurately as a change in the surface area may allow more or less osmosis to occur. The weight and length ...

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