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Investigate Osmosis in potato cell using different concentrations of sugar solutions.

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Osmosis Investigation Aim: To Investigate Osmosis in potato cell using different concentrations of sugar solutions. Scientific Knowledge: Osmosis is the diffusion of water molecules from a region high water concentration to an area of low water concentration through a semi permeable membrane. Thus equalizing the conditions on either side of the membrane. A semi permeable membrane is a very thin layer of material -cell membranes are also semi permeable membranes- which allow small molecules including oxygen, water, carbon dioxide, ammonia, glucose, and amino acids to fit through (pass through) the little gaps in the membrane and prevent bigger molecules like sucrose, starch, protein passing through because the are to big to fit through the gaps. A region of high water concentration is a very dilute solution of sugar or just pure water where there is lots of water molecules causing a high water concentration. Whereas an area of low water concentration is an area with very few water molecules like in a very strong sugar solution because there are more sugar molecules than water molecules. If you place potato strip in pure water then they could become turgid this means the potato strip will become firmer and swell up. This happens because water molecules have distributed themselves from a high concentration around the potato to a low concentration in the potato cells(endosmosis), thus making the water molecules equal on both sides of the potato membrane and making the potato turgid. This will stop when the water is equal in the potato and in the solution. ...read more.


I will achieve this by keeping a water bath nearby. I must also make sure that the potato strips are in the solutions all for the same amount of time. Which will be 20 minutes each beaker. This will be kept to using a stopwatch. This could affect my investigation because if the strips are in longer or for a shorter time the results won't be reliable. This is because more or less osmosis could occur in different strips. The size of the potato strips must be as equal as I can make it. I will measure each strip making sure that they are all 30mm although I would rather have weighed them on a scale. Unfortunately I didn't have one. This is a factor to control because when I take them out of the solution and measure them I will not now how osmosis has affected the potato strip because the length wasn't the same as the rest when it went into the solution, so the rate of osmosis or the difference between each strip will not be reliable. I must make sure that none of the solutions are contaminated with anything apart from the amount of sugar dissolved into the right beakers. This may happen while mixing the solutions if the same mixing instrument is used or if a little bit of sugar spills into the wrong beaker or even if I accidentally mix the solutions up. So to prevent this I will have the beakers marked and will not put anything in the beaker if it has been in a different beaker already (when I measure the temperature I will wipe the thermometer clean first) ...read more.


* Make sure all temperatures are between 23-24�C * Core a potato * Using the cored pieces cut 18 disks that has a circumference of 20mm * I will place 3 into the first beaker while starting a stopwatch. * As soon as the stopwatch shows 10 minutes I will place three more disks into the second beaker * Upon doing this I will restart the stopwatch * When 10 minutes is again shown on the stopwatch I will restart the stopwatch. * At this very time I will remove the first three potato disks from the beaker and measure them. I will enter the results into the table. * I will also put three more disks into the next beaker while doing the previous two steps. * I will then repeat the last six steps until I get 18 results from six different beakers, noting them down as I go along. Results Length of Potato Strips after 20 minutes (mm) Solutions Strip 1(mm) Strip 2 (mm) Strip 3 (mm) Temp. (�C) Average (mm) Pure Water 19 20 20 24 20 10% 17 17 18 23 17 20% 17 16 17 23 17 30% 16 17 16 23 16 40% 15 16 15 23 15 50% 15 15 16 23.5 15 Each potato strip was 20mm at the start. Solutions Size of potato at start (mm) Average size after 20minutes (mm) Increase or decrease (mm) Pure Water 20 20 0 10% 20 17 -3 20% 20 17 -3 30% 20 16 -4 40% 20 15 -5 50% 20 15 -5 Note: all results have been rounded up to the nearest mm ...read more.

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