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Osmosis experiment

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Introduction

Osmosis experiment Aim: My main aim in this experiment is to find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose and water. Introduction: Osmosis is the diffusion of water molecules, down a water potential gradient, across a partially permeable membrane. If the solutions on each side of the partially permeable membrane are equally concentrated then there will be no net movement of water across the membrane. If the solution outside the cell has a low concentration of solute, this causes cells to become turgid as water flows into them, or if the solution outside the cell is of high concentration the cells become plasmolysed as the water flows out. Even if the solute concentration external to the cell is low relative to the vacuole contents, cell will not continue to take in water by osmosis for ever. The cellulose cell wall prevents this. A cell that is full of water is said to be turgid and cannot expand further as the outward pressure on the cell wall is balanced by the inward force of the stretched wall.. At the other extreme, a cell placed in a solution that is high relative to the cell contents will lose water by osmosis. The cytoplasm will cease to exert a pressure on the cellulose cell wall and the cell, described as flaccid, will lack support. Water loss can continue to such an extent that the cytoplasm, and attached cell membrane, contracts and detaches from the cell wall. ...read more.

Middle

I will use a volume of 30mL for each solution. - I will then wash the fresh potato and place it on a piece of paper. I will then use the No.2 Cork borer and No 3. Cylinder plunger to form potato tubers. - I will plunge twenty-four tubers, four for each Petri dish. - I will then place the potato tubers onto a graph paper. - I will use a washed razor blade to cut the potato tubers to exactly four centimetres. I will remove the potato skin in the process. - I will now place each potato tuber onto filter paper and measure its mass on the weight scale. I will record these readings. - I will now place four potato tubers into each Petri dish. - I will then pour 30mL of each solution into its corresponding Petri dish, noting the time when the solution is poured. - I will close each Petri dish and keep them aside for twenty-four hours. - After a day, I will check the potato tubers and note its appearance; if there are any differences. - I will then note the mass of each potato tuber and will take the average. - I will also take the length of each potato tuber and note the difference in length. Method 2: 1) I will cut out twelve potato chips, with a scalpel, all with the identical dimensions of 8x7x20mm. 2) I will weigh each of the potato chips and record their masses in a table, labelling half of them A and the other half B, a pink streak of felt tip pen will denote B. ...read more.

Conclusion

So just taking extra time and care with the cutting would make it more accurate. I could have done more work. I could have done the experiment more times to gain a more accurate result . Also I could test more of a range of concentrations - again to obtain a more accurate result. Also I could experiment with exposing the same weight pieces, but with different surface areas. This would be interesting to do. The results were perhaps a bit undetermined here and there. I think this could have been from one, if not more of the above factors. If I was to repeat the experiment again then I would go to a higher concentration to see what happens in relation to the cell wall. And exactly how much osmosis is able to occur and what would happen to the cell and its wall when it reached the limit. The reason I would do this as I think it would be both interesting and beneficial to see what the capabilities of the cell and its cell walls were. Also if I were to do it again I would test more values of concentration. For example I tested 0,0.5,1,1.5,2. Then I would go in to more values like 0,0.25,0.5,0 .75,1, 1.25.....etc. The reason for this is I feel it would provide me with more accurate results to base my graph and theories on. Also I would like to see how the surface area would affect osmosis. This is because I feel that it would be interesting to know what affect it has and to compare it to the other set of results I obtained. ...read more.

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Related GCSE Life Processes & Cells essays

  1. Marked by a teacher

    To determine the water potential of a potato tuber cell using varying salt solution.

    5 star(s)

    This means that, as I had predicted the water potential within the cell was less than outside the cell therefore water entered the cell. The water has entered the cell and caused the protoplast to press against the cell wall this is how the cell has swollen and turgid, this effectively increased the mass of the cell.

  2. Osmosis is defined as 'the movement of water molecules from an area of high ...

    This is the exact opposite of "turgid". The contents of the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed. When plant cells are placed in a solution, which has exactly the same osmotic strength as the cells, they are in a state between turgidity and flaccidity.

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