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Factors Affecting Osmosis In Plant Tissue

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Factors Affecting Osmosis In Plant Tissue Aim: To observe how concentration affects Osmosis by calculating the difference of length, weight and diameter before and after the experiment. Plan: Osmosis is the transportation of water through a plant membrane. This membrane allows water molecules through but not sugar molecules, as they are larger, this is called a semi-permeable membrane. The sugar molecules are scientifically named solutes as they dissolve in the water, which is the main purpose for osmosis. As the more water that is transported through the semi-permeable membrane the more sugar dissolves, which can then be transported through the plant for photosynthesis to occur. The water also gives support for young plants that would wilt without it. The solute molecules are already in the plant cells but need the water from the surroundings, so the semi-permeable membrane allows transportation from a low to a high concentration. This may seem illogical until a microscopic view of the process of osmosis is shown and explained below. This process is possible because of the difference in kinetic energy, as the water molecules have a high kinetic energy to pass through the membrane, but when they react with the sugar they join there energy so have less. This gives an idea on why osmosis can occur as the low concentration has more energy to transport than the high concentration. As the high concentration has more particles within it, it so in turn has a higher pressure, which means that osmosis increases the concentration and the pressure of the plant cells. This would be a problem if it were not for the sufficient strength of the cell wall to withstand the change in pressure, as it is this pressure that keeps the cells rigid. Osmosis maintains the turgor of the cells. However if the concentration were stronger in the surroundings of the plant cells, as this was submerged in a stronger solution, then the water from inside the plant cells would transport into the higher concentration. ...read more.


This is known as osmosis. The change in whether the surrounding solution is less or more is known as the osmotic potential, which will be studied in the main experiment. I also can predict that the shape and correlation of the graph for mass, length and diameter will all increase as the concentration decreases. This will occur, as osmosis will be shown rather than plasmolysis because the point of the experiment is decreasing the concentration not increasing. However if the results were upturned then plasmolysis would be the factor and the graph would decrease in correlation. So the graph can be seen accurately from either angle, it can be inverted. Method: In this experiment, five different concentrations will be used: > 1M (100% sucrose solution) > 0.75M (three parts sucrose, one part water) > 0.5M (two parts sucrose, two parts water) > 0.25M (one part sucrose, three parts water) > 0M (100% distilled water) For each concentration there will be four potato pieces, to give an accurate result with mean of the four pieces for each solution. All the potato pieces will begin at the same length, diameter and near to the same mass. The reason that we will be using five different concentrations and repeating the experiment with four similar chips, is because accuracy and reliability is needed to produce reasonable evidence to back up my knowledge and prediction on osmosis and information that surrounds this topic. The same volume of liquid will be poured into each test tube, which will have one chip each in there. These test tubes will be separated into groups of their concentrations and put in beakers full of water to keep the temperature constant. This will then be left for a specified time and the difference in mass, length and diameter will be displayed at the end in a table and graphically. Results: (after twenty hours and two minutes) ...read more.


On the mass graph the 1M solution had an anomalous reading because of the data that read 1.16g, which heightened the placing of the average on the graph. In the 0.5M solution was greatly decreased in its placing by the reading of 1.26g. In the diameter graph the 0.75M solution was anomalous because of the fact that it was exactly the same as the reading in the stronger solution. This cannot be correct, as the correlation of the graph must change hopefully by increasing to show osmosis. The other anomalous reading is in the 0M solution where two are far away from the average point. Finally the length graph is consistently anomalous, with every reading having one or more repeats distant from the average so reasoning why the osmotic potential states to be past 0M. When considering the collected data and the method used, improvements could have been made if the preparation and accuracy of the length of the chips had been undergone. This would have lowered the amount of anomalous readings and so a better conclusion could have been drawn on the true correlation and osmotic potential of potato chips in different concentrations. Then the osmotic potential on the graph could have been taken further to find the concentration at which osmosis and plasmolysis occurs. If preparation time had been increased this would have greatened the reliability of results and this could have been increased further if more concentrations were tried with only three chips in each instead of four. This is stated because the amount of chips was too many and so averaged the data in an unreliable way. Finally an extension to this experiment to increase the reliability and accuracy would be to use different plant cells (rhubarb or liver) to have a range of cells to experiment on. This would be useful in discovering how other plants or animals transport water and whether or not they use osmosis in the same consistent way. With this data a conclusion for similarities and differences between different cells could be made and how concentration affects the rate of those cells with osmosis. ...read more.

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