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To find out how different concentrations of sucrose solution affect the incipient plasmolysis of different root vegetables until the isotonic point has been reached.

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Introduction

AS Biology Coursework Introduction: - to find out how different concentrations of sucrose solution affect the incipient plasmolysis of different root vegetables until the isotonic point has been reached. Prediction Osmosis is defined as the net movement of water molecules from a region of high water potential to a region of low water potential across a partially permeable membrane down the concentration gradient. A partially permeable membrane allows some molecule to diffuse through but not all, if the molecules are small enough like water molecules then they can diffuse through easily but large solute molecules can't pass through. The water molecules will diffuse both ways through the partially permeable membrane however the net movement will be to the side with a lower concentration of water molecules. Water potential is the potential of water molecules to diffuse out of a solution, also water molecules are more likely to diffuse out of a solution containing a higher concentration of water molecules and they are less likely to diffuse out of a solution containing a lower concentration of water molecules. Pure water contains the highest water potential which is zero kilopascals 0(?) All solutions have a lower water potential then pure water hence there water potentials are always negative, the more solute molecules present the lower more negative the water potential. The water potential inside cells can be calculated depending on two factors: Water Potential (?) = Solute Potential (?s) + Pressure Potential (?p) The solute potential is the amount of solute molecules in a solution, the more solute molecules present the more weak chemical bonds formed with the water molecules slow down their movement. Pressure Potential is caused by the existence of cell membranes and cell walls in plants, these exert a strong inward pressure on the cell and this can effectively be squeezing water molecules out of the cell. Solutions that have the same solute potential and water potential are isotonic which means Water Potential = Solute Potential. ...read more.

Middle

13) Dry off any excess water using a paper towel and measure the length using an accurate ruler also weigh all the cylinders and record the appropriate mass in the 'after' section in the results table. Equations needed to calculate the percentage increase/ decrease in the mass and length of each root vegetable. Mass = End mass- start mass � start mass x 100 Length = End length- start length � start length x 100 Results Swede Solution (Molar) 0.3 0.4 0.5 0.6 0.7 Before After Before After Before After Before After Before After Run 1 1.43 1.48 1.37 1.39 1.48 1.46 1.46 1.40 1.53 1.45 Run 2 1.45 1.46 1.45 1.49 1.45 1.44 1.44 1.41 1.43 1.36 Run 3 1.47 1.48 1.53 1.52 1.41 1.39 1.43 1.35 1.48 1.39 Mean 1.45 1.47 1.45 1.46 1.45 1.43 1.44 1.38 1.48 1.40 Difference (g) 0.02 0.01 -0.02 -0.06 -0.08 Percentage Change (%) 1.36 0.68 -1.38 -4.43 -5.41 Solution (Molar) 0.3 0.4 0.5 0.6 0.7 Before After Before After Before After Before After Before After Run 1 30 30 30 30 30 28 30 27 30 26 Run 2 30 32 30 29 30 29 30 26 30 27 Run 3 30 31 30 31 30 30 30 29 30 26 Mean 30.0 31.0 30.0 29.0 30.0 29 30 27.6 30 26.7 Difference (mm) 1.00 -1.00 -0.3 -2.40 -3.30 Percentage Change (%) 3.23 -3.33 -3.33 -8.00 -11.00 Parsnip Solution (Molar) 0.3 0.4 0.5 0.6 0.7 Before After Before After Before After Before After Before After Run 1 1.36 1.37 1.27 1.21 1.33 1.27 1.29 1.18 1.35 1.16 Run 2 1.30 1.31 1.22 1.19 1.29 1.23 1.22 1.14 1.32 1.18 Run 3 1.30 1.34 1.20 1.17 1.23 1.16 1.27 1.19 1.22 1.17 Mean 1.32 1.34 1.23 1.19 1.28 1.22 1.26 1.17 1.30 1.17 Difference (g) 0.02 -0.04 -0.06 -0.09 -0.13 Percentage Change (%) 1.49 -3.25 -4.69 -7.14 -10.00 Solution (Molar) ...read more.

Conclusion

To prevent this from happening use the same 30mm ruler for each root vegetable and make sure you are focused and concentration on what you are doing. An additional human error which could have altered the results was when measuring the masses of the different root vegetable cylinders on the electronic balance, this could have been caused by a distraction and a inaccurate value may have been recorded, next time I will carry out my experiment where there is no distractions so there will be a lower chance of recording an inaccurate result. This could have been another factor which caused one or more of the anonymous results. Furthermore when placing the root vegetable cylinder on the electronic balance it might not have been set to 0.00g therefore this could change the overall mass of the cylinder which could lead to more inaccuracies, to avoid this problem I will make sure the electronic balance is set to 0.00g before I place the cylinder on it as this will give a more reliable and accurate mass. Also if there was water on the balance and it didn't get cleaned and you placed a root vegetable cylinder on there to record its mass, it would result in an error being made because the water on the electronic balance will add to the mass of the root vegetable cylinder and therefore result in inaccuracies, this will result in anonymous results. The experiment which I did had some anonymous results which may have been caused by the errors such as lack of concentration, becoming distracted. I think my results are valid under the circumstances the experiment occurred, the limitations which occurred were mainly out of my control and if I was to repeat the experiment I would use more reliable equipment, a wider range of root vegetables and repeat the experiment more times to get good precise, reliable results. ...read more.

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