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Osmosis In Potato Tissue

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OSMOSIS IN POTATO TISSUE GCSE Biology - Experiment report Osmosis is a specialised form of diffusion, a process in which molecules move across a semi-permeable membrane. Osmosis applies specifically to water molecules that behave in this way, moving from a region of high water concentration to a region of low water concentration. Also known as moving down a concentration gradient, this movement can be best described below: N.B - The sugar particles are too large to pass through the semi-permeable membrane. D The process happens only in one direction, as shown by the arrows in the diagram above. It is important to remember that osmosis will take place whenever two solutions of water of differing concentrations, are separated by a selectively permeable membrane. Osmosis takes place throughout both plant and animal cells, and has differing effects in both mediums. Because all plant cells incorporate a rigid cell wall, plant cells are allowed to swell and become turgid. This process of turgor is an important feature of land dwelling plant-life. The turgor causes support for leaves, enabling photosynthesis to take place. In animal cells, osmosis has a very different effect. If a blood cell were immersed in water, it would swell and would eventually burst. This effect is combated by a natural clause; the concentration of the water in the cells is the same as the concentration of that outside the cell, in the bloodstream. In any investigation, the variable aspects of the experiment must be taken into careful consideration. ...read more.


iii) Two potato tubes will be placed into each boiling tube and will be left to stand for twenty-four hours. The potato chips will be removed, dried and re-weighed. Any change in mass will be noted, using the readings taken before and after the tubes' immersion in sugar solution. As mentioned earlier, the concentration of the sugar solution will vary from one boiling tube to another. The first boiling tube will contain a solution of ratio 20:0 (sugar : water) and progress through six steps to 0:20, altering each substance by 4ml each step. It is important that the total volume of water and sucrose in each boiling tube equals 20ml. The change in mass noted after 24 hours will be dependent on the molarity (or ratio) of the sugar solution in each particular boiling tube. Boiling tube No. Volume of Water Volume of sugar Molarity 1 0ml 20ml 1.0 2 4ml 16ml 0.8 3 8ml 12ml 0.6 4 12ml 8ml 0.4 5 16ml 4ml 0.2 6 20ml 0ml 0.0 Table 1 N.B - The molarity of the sugar solution tells you how strong the solution. Eg. A solution of molarity 1.0 is comprised of 100% sugar. A solution of molarity 0.4 is comprised of 40% sugar, 60% water etc. RESULTS: Two sets of results will be taken: the mass of the potato tubes before the immersion in the sugar solution, and the mass of the tubes after the experiment. The results will be displayed in two forms, tabular and graphical. ...read more.


An appropriate amount of readings were taken, as there is enough to be able to analyse the results, but not so many as that the analysis becomes harder. The reason why two tubes were tested in each tube is that the experiment is effectively being repeated. The method that was used in this experiment was the best possible. It kept all the variables but one the same, and dealt only with changing the concentration of the sugar solution. If the experiment were to be repeated, I would not test two tubes of potato in the same boiling tube, I would test them in separate boiling tubes. This would make the test fairer, as it proves that the presence of the second tube is not affecting the osmotic actions of the first. This modification will also ensure that each potato tube is immersed in the same amount of water. Placing two tubes in the same receptacle could mean that one of the tubes takes up water faster than the other. The evidence collected was sufficient enough for me to make a conclusion. Apart from the modification mentioned earlier, there are no other tests that could be applied to enhance the experiment. The readings that were taken were to a sufficient degree of accuracy, because a pair of electronic scales was used to pinpoint the tubes' weights to two decimal places. Overall, I believe that the experiment was planned and completed to an adequate standard. The results table is clearly set out and diagrams help to explain the principles of osmosis. The graph is also accurate and shows the pattern well. ...read more.

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