The effect of sugar concentration on potato tubers.

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The effect of sugar concentration on potato tubers

Aim;

I will be carrying out this experiment to investigate the effects reflected on a potato tuber; which is left in sugar solutions of various concentrations.

Prediction;

I predict that the more dilute (the solution with more water than sugar in it) will result with the potato's mass increasing. I base this prediction on the knowledge I have about osmosis. Osmosis is the term given for the process of water passing through a semi-permeable membrane from the less concentrated solution to a more concentrated solution.

If, as in diagram 1, the potato tuber has a higher sugar concentrate than the sugar solution surrounding it, osmosis will take place into the potato, causing the potato in the solution to swell. This is because the plant cells; which make up the potato have become turgid, So that the cytoplasm is pushing outwards onto the cell wall. (Please refer to diagram 2 on separate sheet)

To find out how much water the potato is able to take in you may use a simple potometer. The potato takes up water through a capillary tube as shown in diagram 4. The rate of up take can be measured by allowing a small air bubble to enter the tube. The bubble must be ejected from the capillary tube by squeezing the plastic tube, and must not be allowed to enter the plastic tube. To find out how much water the potato has taken in, just read off where the bubble is. You should leave this experiment standing until there is no noticeable change and the reading will give you how much water the potato will absorb until osmosis is no longer possible. (As read from 'Text III The maintenance of life').

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There is another way, however it is not as accurate, You could carry out the proposed experiment draw up the graph, and using it, you could draw in the estimated equilibrium point as I have done.

Once the potato tuber in the test tube has reached the same ratio of sugar: water as the solution surrounding it the process will stop as osmosis will only take place where there is a separation of low and high concentrate, there fore there will be no change in weight.

How ever if the situation is reversed and there is a lower concentration of ...

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