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Investigation to find the Water Potential of Apple Tissue

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Introduction

Investigation to find the Water Potential of Apple Tissue Introduction The water molecules move in and out of the cell through the partially permeable cell membrane by the process of Osmosis. The definition of osmosis as given in "Understanding Biology For A-level, Fourth Edition" by "Susan and Glenn Toole" is as follows, "the passage of water from a region where it is highly concentrated to a region where its concentration is lower, through a partially permeable membrane." Diagram of Osmosis This investigation is to establish the exact water potential of apple tissue. The definition of water potential, as written in "Biology 1" endorsed by OCR "Water potential is the tendency of a solution to lose water; water moves from a solution with high water potential to one with low water potential. Water potential is decreased by the addition of a solute, and increased by the application of pressure. Symbol is ?" This is called moving down a water potential gradient. When the water potential in both regions is equal both areas are in equilibrium and there is not further net movement of molecules. The water potential of a cell is determined by two factors: the solute potential in the cell (?s), and the pressure potential (?p). * The solute potential (?s) is a measure of the reduction in water potential due to the presence of solute molecules. It is the negative component of water potential, sometimes referred to as the osmotic potential or osmotic pressure. ...read more.

Middle

5. I also need to find the percentage change by dividing the change in by the initial and multiplying by 100 for both length and mass. Results for Preliminary Test 1 Concentration Mass before/g Mass after/g Change in mass/g % Change in mass /Mol 1 2 Mean 1 2 Mean 1 2 Mean 1 2 Mean 0.0 0.87 0.87 0.87 0.85 0.82 0.835 -0.020 -0.050 -0.035 -2.30 -5.75 -4.02 0.2 0.92 0.92 0.92 0.87 0.90 0.885 -0.050 -0.020 -0.035 -5.43 -2.17 -3.80 0.4 0.92 0.90 0.91 0.90 0.94 0.92 -0.020 0.040 0.010 -2.17 4.44 1.10 0.6 0.86 0.83 0.845 0.90 0.85 0.875 0.040 0.020 0.030 4.65 2.41 3.55 0.8 0.91 0.88 0.895 0.87 0.83 0.85 -0.040 -0.050 -0.045 -4.40 -5.68 -5.03 1.0 0.93 0.90 0.915 0.78 0.75 0.765 -1.150 -0.150 -0.150 -16.13 -16.67 -16.39 Concentration Length before/mm Length after/mm Change in Length/mm % Change in Length /Mol 1 2 Mean 1 2 Mean 1 2 Mean 1 2 Mean 0.0 50 50 50 50 51 50.5 0 1 0.5 0 2 1 0.2 50 50 50 51 50 50.5 1 0 0.5 2 0 1 0.4 50 50 50 51 52 51.5 1 2 1.5 2 4 3 0.6 50 50 50 51 51 51 1 1 1 2 2 2 0.8 50 50 50 48 49 48.5 -2 -1 -1.5 -4 -2 -3 1.0 50 50 50 47 46 46.5 -3 -4 -3.5 -6 -8 -7 Preliminary Test 2: to find what shape to use I also needed ...read more.

Conclusion

It was also very difficult to cut the strips into exactly the right thickness and the masses were much less than the cores. By using a cork borer, it ensures the diameter of each piece of apple is always the same and the only measurement I have to cut by hand is the length, this reduces risk of inaccuracy within the results. From the preliminary tests I can tell that apple tissue has a very high sugar content so the solute concentration will be higher than the one demonstrated. I can also conclude that I will use a range of concentrations around 0.2M and 0.8M concentrations. This is because I am trying to find the exact point at which the molarity of the solution causes the percentage change = 0. If the results were drawn on the graph, this would be the point at which the curve crossed the x-axis, thus showing the concentration of sucrose within the apple tissue. I will also use four pieces of apple instead of two to allow a greater range of results to get a much more accurate mean average. This would also make it easier to see any anomalies. Prediction Using my preliminary tests I can estimate the sucrose concentration of apple tissue to be between 0.4M and 0.8M, and therefore the water potential will also be between 0.4M and 0.8M. The results of the main experiment will conclude whether this hypothesis is accurate or not. ?? ?? ?? ?? ...read more.

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