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The purpose of my investigation is to find out the concentration of the cell sap in potato cells.

Extracts from this document...

Introduction

Biology Science Investigation The purpose of my investigation is to find out the concentration of the cell sap in potato cells. To do this I will need to place potato pieces in different concentrations of sucrose. Water will pass in and out of the cell through osmosis meaning that the potatoes will lose or gain mass and there will be one that has the same mass at the beginning and end of the experiment. The solution that the potato is in will equal the concentration of the cell sap. Before I can do this experiment I will need to find out what is involved in the process of osmosis and what causes it to stop. According to "Encarta" osmosis, is when water diffuses from a solution of low concentration to a solution of high concentration through a semi-permeable membrane. Diffusion is the movement of molecules from a region in which they are highly concentrated to a region in which they are less concentrated. When a substance like sugar dissolves in water, the sugar molecules attract some of the water molecules and stop the from moving freely. This reduces the concentration of water molecules. In my diagram below you can see that the half of the water molecules on the right side have been attached to the sugar molecules. There are more free water molecules on the left of the membrane then on the right, so the water will diffuse quicker from left to right across the membrane than from right to left. ...read more.

Middle

This is because the cell concentration and the solution concentration is exactly the same and osmosis has not occurred. The formula to figure out the percentage increase is The potato will be cored giving it the same width and dimensions and then stored in water. Then 6 pieces of the potato will then by dried and cut in to three pieces of 1cm in length, weighed then the pieces will be placed in boiling tubes containing solutions of sucrose, with the concentrations varying from 0%(pure water) - 10%. Three pieces of potato will be placed in each and the volumes of the solution will 5cm. The weight will be given to two decimal places and The average of the three potato pieces on each boiling tube will be taken. The test tubes would usually be left for 24hours and then taken out of the solutions, dried and weighed again and the average taken. Results 1st Experiment Mass before Mass after Sucrose Concentration (%) Mass (g) Ave Mass (g) Mass (g) Ave Mass (g) 1st piece 2nd piece 3rd piece 1st piece 2nd piece 3rd piece 0 0.99 1.03 1.06 1.03 0.79 0.77 0.77 0.78 2 1.07 1.00 1.10 1.06 0.72 0.80 0.86 0.79 4 1.01 1.12 0.99 1.04 0.80 0.71 0.65 0.72 6 1.10 1.13 0.82 1.02 0.68 0.79 0.88 0.78 8 1.07 1.07 0.99 1.04 0.88 0.74 0.79 0.80 10 1.06 1.01 0.91 0.99 0.86 0.95 1.00 0.94 2nd Experiment Mass before Mass after Sucrose Concentration (%) ...read more.

Conclusion

Or perhaps the potato chip was not cut accurately, or that part of the potatoes, cells did not loose/gain mass well, this may have been because the potatoes were put in water before the experiment and osmosis may have already occurred causing water to diffuse out of all potato cells when I started the experiment. My results did vary a lot for the same concentration. The fact that a certain part of the potato may not be the same as another was shown as the chips all of the same length was not the same weight. I could extend my enquiry by testing the percentage change in mass with sugar solution using a different substance. By this I mean using a different vegetable. Then I could find out whether osmosis occurs with the same patterns and trends with any vegetable. Such as carrots. The carrot would be cut into 18 pieces with the same length and width. The pieces will then be weighed and the average taken and three pieces will be placed in boiling tubes each containing different sugar concentrations ranging from 0% to 10%. The test tubes will be left for 24 hours and then they would be taken out of the solution weighed again and the average taken. The percentage increase would be found out using the formula. I could also find out if the same patterns and trends occur in osmosis with different solutions such as salt. I would follow the same method as I mentioned above except I will use salt solution instead of sugar ...read more.

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