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To determine the concentration of the cell sap in potato storage tissue. By using Osmosis, determine what the sugar concentration of cell sap is.

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Introduction

Biology Coursework Emmeline Hastings Aim: To determine the concentration of the cell sap in potato storage tissue. By using Osmosis, determine what the sugar concentration of cell sap is. Prediction I predict that the potato segment in the distilled water will definitely gain in weight because the solution outside it has a much higher concentration of water then in the cell sap meaning Osmosis will occur and the potato segment take in water. I predict that 0.2M sugar solution will also gain weight because it still has quite a high concentration of water outside the potato. The potato in the 0.4M solution will gain weight but the potato in the 0.6M and 0.8M solutions will lose weight. The glucose concentration of the cell sap will be between 0.4M and 0.5M. Scientific Knowledge This experiment is based on the concept of Osmosis. Osmosis is the diffusion of water molecules from a region of high water concentration to a low water concentration through a semi permeable membrane (in this case, the cell potato cell membrane). The cell walls of the potato cells are semi permeable meaning that water molecules (which are small) can fit through but other bigger molecules such as glucose cannot pass through. The water molecules can flow both ways through the membrane, letting molecules both in and out. The Kinetic theory states that all molecules of every substance have energy which causes them to move about for example a chemical reaction can be accelerated through heating because the molecules gain more energy efficiently causing harder and more effective collisions of the molecules. ...read more.

Middle

Surface area would affect the rate of Osmosis by allowing more area for the water to enter or exit. The weight of the potato will effect the results because if one potato piece is larger then another it will have more water inside it. * Each sugar solution will be measured to the same amount for each boiling tube (30 ml). * All boiling tubes will be kept in the same area so that no effects are made by differentiating environments. * All water used in the experiment will be distilled and without any impurities that may effect the rate of Osmosis. * I will repeat the experiment twice and use 5 different sugar solutions to achieve a good set of results that with facilitate my analysis. Variables * The range of sugar solutions used i.e. 0.2M, 0.4M etc. Constants * Temperature * Start mass of Potato segments * Measurement of sugar solution potato segments are put in (30 ml). Safety This experiment is not very dangerous, but the sugar solutions are sticky and messy. I must be careful using the cork borer and the Scalpel, as they are a potential hazard. Results Test One Test Two Solution (M) Start mass (g) Finish mass (g) Difference (g) Start Mass (g) Finish Mass (g) Difference (g) Average Difference (g) 0.0M 1.40 1.81 0.41 1.40 1.77 0.30 0.39 0.2M 1.40 1.48 0.08 1.40 1.50 0.10 0.09 0.4M 1.40 1.37 -0.03 1.40 1.37 -0.03 -0.03 0.6M 1.40 1.10 -0.30 1.40 1.06 -0.34 -0.32 0.8M 1.40 0.88 -0.52 1.40 0.92 -0.48 -0.5 Graphs of Results Analysis From ...read more.

Conclusion

This alters my found Glucose concentration of the cell sap but still leaves me with a fairly accurate result. Improvements could be made to obtain a far more reliable result. In order to have made my investigation more accurate I could have spent more time on making the potato segments more equal in weight, I could also have used a larger and more informative set of glucose solutions: 0.25M, 0.35M, 0.45M, 0.55M. By using a closer and narrower range of solutions, the concentration of the cell sap could be found more accurately. I could have monitored room temperature and any other environmental changes that could also affect the experiment such as light intensity. I could have done this by keeping the light intensity constant by using an electric lamp. By repeating the experiment a greater number of times my averages would be made that little but more precise. Also to extend the experiment, because the Glucose concentration of the cell sap that I found is not entirely accurate, I could repeat the experiment but this time using a range of glucose solutions that the concentration may be. For example 0.32M, 0.34M, 0.36M, and so on. This would offer me a more accurate and reliable result to the experiment. I also hypothesise that the experiment is still accurate if all constants are kept constant, and that if an environmental change occurs, as long as it occurs to all of the solutions in equal amounts, the results would not be altered. I could extend the experiment by proving this hypothesis. ...read more.

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