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Investigation to work out the concentration in potato cell sap

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Introduction

Sarah Carr Biology Coursework 2001 Investigation to work out the concentration in potato cell sap Preliminary work As an introduction to osmosis, an experiment was carried out with a model cell. The model cell experiment shown how osmosis occurs, demonstrated with two cells - Cell A Cell B Water diffuses into 'cell' Water diffuses out of 'cell' Visking Visking Tubing Tubing (Partially (Partially Permeable Permeable Membrane) Membrane) Cell A was filled with sugar solution, cell B was filled with water, and then the two cells were weighed. Cell A was placed into a beaker of water and cell B was placed into a beaker of sugar solution. They were both left for 30 minutes, and then the cells were weighed again. It was discovered that cell A (containing sugar solution), increased in weight. This was because water was allowed to pass into the cell and into the strong solution by osmosis. Therefore cell B, decreased in weight because water had passed out of the cell and into the strong solution by osmosis again. ...read more.

Middle

to cut samples of potato in the same diameter * Scalpel * Ruler * White tile * 25 cm3 measuring cylinder * Top pan balance * Paper towels Diagram Method The equipment needed to carry out the experiment was set up according to the diagram. Seven test tubes were labelled with concentration levels and placed in order, in the test tube rack. 10ml of each sugar solution (1/32, 1/16, 1/8, 1/4, 1/2) was placed into the labelled test tubes; 10ml of 1/32 sugar solution into the tube labelled 1/32 and so on. After this was completed seven pieces of potato were cut out with a cork borer, and then cut to a length of 1.5 cm (15mm). The pieces of potato were then weighed separately, the weights were recorded and then the potatoes were placed into the test tubes. The time was noted and each potato piece was left in the solution for 30 minutes. After this time, the solutions were poured away and each potato piece was taken out of the tubes and weighed separately. ...read more.

Conclusion

Each piece of potato should be placed in the solution at the same time. Secondary sources Biology for you - textbook From this textbook I researched information about osmosis and the model cell experiment. Diagrams have also been taken from the same textbook. Results Experiment 1 Solution strength Start weight Finish weight Difference (decimal) Difference (percentage) 1 1.10g 0.97g 0.13 -11.8% 1/2 0.91g 0.90g 0.01 -1.1% 1/4 0.85g 0.86g 0.05 -5.8% 1/8 1.03g 1.06g 0.03 +2.9% 1/16 0.85g 0.82g 0.03 +3.5% 1/32 1.13g 1.16g 0.03 +2.7% Distilled 0.76g 0.81g 0.05 +6.6% Experiment 2 Solution strength Start weight Finish weight Difference (decimal) Difference (percentage) 1 0.91 0.87 0.04 -4.3 1/2 0.91 0.91 0.01 -1.1 1/4 0.86 0.90 0.04 +4.7 1/8 0.90 0.94 0.04 +4.4 1/16 0.80 0.84 0.04 +5.0 1/32 0.81 0.84 0.03 +3.7 Distilled 0.99 1.03 0.04 +4.0 Using these results I am able to plot these values on a line graph, where the x-axis is concentration and the y-axis is percentage change in weight. A line of best fit is included in both graphs; the concentration of potato cell sap can be discovered from this. ...read more.

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