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Investigating osmosis in plant tissue.

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Introduction

Investigating osmosis in plant tissue Introduction Osmosis is the movement of water particles along a concentration gradient, from a high concentration to a low concentration through a selectively permeable membrane. Osmosis can happen anywhere where there is a selectively permeable membrane and water, however can only move along the concentration gradient. For example if a red blood cell were to be placed in water, then water would travel through diffusion into the red blood cell as the water concentration inside a red blood cell is quite low. However animal cells only have a cell membrane, so the blood cell would fill and fill, and keep on filling until the membrane could hold it no longer and it would burst. Whereas with a plant cell, it has a cell wall, so instead of bursting, a plant cell will merely become turgid, or swollen and hard. This is where the pressure inside the plant cell increases and increases until no more water can enter and the cell is turgid. This is the pressure is called turgid pressure and keeps plants standing up, and why plants wilt when not enough water is consumed by the plant, this is called flaccid. ...read more.

Middle

could affect osmosis, and we know that the volume, size and surface area of each cylinder is the same, and as they are all from the same potato, the only variable that we are altering is the concentration of the solution. When conducting the experiment we need to remember to keep it a fair test, whilst doing so we need to consider these things: -Keep the potato samples the same length (2cm). This is because if one potato sample is 1cm long and one is 3cm long then the 3cm long sample will have a larger surface area and osmosis will occur much faster -Average: To make the experiment as accurate as possible an average will be taken out of 3 results for each solution taken. This is so that we can determine which results are accurate and which are anomalous. Trial experiment Molarity Mass at 0mins 15mins 30mins 45mins 60mins %Mass change 0 4.83 5.25 4.97 5.02 5.01 3.72 0 4.68 5.16 5.33 5.42 5.41 15.6 0.6 4.21 4.73 4.46 4.36 4.27 1.42 0.6 4.69 5.06 4.63 4.55 4.41 -5.97 1 5.04 4.01 4.2 4.03 3.9 -22.61 1 4.57 4.41 3.8 4.36 4.36 -4.6 In the trial experiment, we discovered that our original experiment plan wasn't quite as good as it could be, and this was true for many reasons. ...read more.

Conclusion

The experiment however apart from certain knocking over incidents was fairly reliable, as long as you considered all the factors that could affect the test and all the precautions you needed to take to make sure it was a fair test the experiment was very reliable. There were however a few limitations, mostly to do with equipment; there weren't nearly enough weighing machines, ergo mass pile ups were cause queueing to use them and times were occasionally missed by some groups, what would have made this much easier would have been to have a mass cooperation from each and every group as to which times and when they could use the weighing machines. There could be a few improvements made for this experiment, what we could have done is have lots of different groups doing one molarity each however lots of times, this would have created much more accurate results and eliminated anomalous results. Another thing that I would like to do is alter all the factors, e.g. size, surface area, temperature and also try it with not only different vegetables but fruit as well. I could also then vary the solution, e.g. instead of sucrose use another liquid substance present in fruit and vegetables. Apart from this I feel the experiment was highly successful and thoroughly enjoyed. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a well structured report that covers most of the necessary aspects of this investigation:
1. The use of subheadings is good but there are several sections with running commentaries.
2. Researched information needs to be referenced.
3. An analysis of the results needs to be carried out.
4. The evaluation shows some understanding of principles but be careful with claims made about accuracy.
***

Marked by teacher Luke Smithen 23/07/2013

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