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Find the concentration of Potato Cell Sap.

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Investigation, to find the concentration of Potato Cell Sap Part 1; Preliminary work and background information which will help me to plan my investigation; The definition of Osmosis Water molecules in a high concentration travel through partially permeable cell membrane to a lower concentration of water molecules. (So water travels from a solution to a strong solution resulting in the dilution of the strong solution). A partially permeable membrane has small pores, which allow small molecules of water to pass through, but bigger solute molecules will not. NB A solution consists of water and solute, e.g. a sucrose solution has water molecules and the solute has sucrose molecules. In Osmosis, water molecules move from where there is a lot to where there are few water molecules, so the water movement is down a concentration gradient. No energy is required. Applied information on Osmosis Water is the weakest solution. It is weaker than the cell sap so water molecules leave the bathing solution and move down a concentration gradient, to enter the cell sap and make the tissue longer. A strong sucrose solution is stronger the cell sap, so water molecules leave the cell sap and move down a concentration gradient. This is in order to dilute the strong sucrose solution. At a certain sucrose concentration, the cell sap will not gain or lose water, therefore the cell sap is the same concentration as this concentration of bathing solution. ...read more.


into each of the first three test tubes. 3. Repeat this for the further five concentrations (0.1, 0.2, 0.3, 0.4 + 0.s Msucrose), making sure that the measuring cylinder is washed out each time the concentration is changed. 4. Label each test tube according to which solution is inside it. 5. Using the size 3 corer cut 18 strips from the potato. 6. Cut each one down to 50mm in length using a ruler and a scalpel. Do this on the tile to prevent ruining the surface. 7. Place one piece of potato into each test tube. 8. Record the time from when the last piece of potato is in it's test tube. 9. Leave the potatoes in the bathing solutions for 24 hours. 10. Draw a table ready to record your results 11. After 24 hours take the first test tube from the stand and tip the contents into a beaker. 12. Using the tweezers, take the strip of potato carefully from the beaker and lay it on the tile. 13. Measure the new length with a ruler and record this in the table. 14. Repeat steps 10, 11 + 12 for the remaining 17 pieces of potato. 15. When all the potatoes have been measured record the time from the clock. ...read more.


My particular results that seem to anomalous are; I don not have any anomalous results. I consider my results to be accurate because; I had three readings for each concentration which together gave an average change in length. The three readings for each concentration were very similar, e.g., 0 M sucrose = +2, +3 and +3 and 0.5 M Sucrose = -4, -4 and -4. The fact that these results are so close, means that my experiment was accurate. Did I collect sufficient evidence to make a conclusion?; Yes, my experiment gave me an exact value for the concentration of the cell sap (where the line crosses the x axis). I f I hadn't enough evidence, I would not have been able to find this. My investigation could be improved by; I took enough reading and I used the correct range (0.0 - 0.5 M Sucrose instead of 0.4 - 0.5 M Sucrose). I did not have any difficulties in doing the experiment. I kept all the other variables constant, by making sure that each experiment was left for the same period of time. I also used the same amount of bathing solution each time. Therefor my results came form a fair test. However if I did this experiment again, I would use a thermostatically controlled water bath, to keep the temperature constant. I would also weigh the potatoes at the beginning and at the end of each experiment in order to obtain a mass reading as well as a length reading. ...read more.

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