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The Factors affecting osmosis in potato tissue.

Extracts from this document...

Introduction

The Factors affecting osmosis in potato tissue. Planning In this coursework I am investigating the factors affecting osmosis in potato tissue. Osmosis is defined as the net movement of water molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell membrane, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed all over an object with no area having a higher or lower concentration than the other. Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become turgid when they are put in dilute solutions. The pressure inside of the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. The liquid pressure works against osmosis. Turgidity is very important to plants because this is what makes the plants stand up to the sunlight. When plant cells become flaccid this is when they loose water by osmosis this is the exact opposite of turgid. The content of the potato cell shrink and pulls away from the cell wall. ...read more.

Middle

There are certain safety precautions that will need to be taken to avoid danger within this experiment. Hair must be tied back to prevent any substances touching the hair. Overalls should be worn so that sucrose solution is not split on clothes. Precautions must be taken when using the cork borer to cut the potato chips to the right size. I predict that the lower the concentration of the sugar solution in the flasks, the larger the mass of the potato chip will be. This is because the water molecules pass from a region of high concentration, i.e. in the water itself to a region of low concentration, i.e. in the potato chip. Therefore the chips in higher water concentrations will have a larger mass than in higher sugar concentrations. The greater the concentration of water in the external solution, the greater the amount of water that enters the cell by osmosis. The smaller the concentration of water in the external solution the greater amount of water that leaves the cell. However, there will be a point where the concentrations of water in inside and outside the potato cells are equal. At this point there will be no change in length, volume and mass of the potato, as the net movement of water will be zero, no osmosis has occurred. At point A the graph suggests that no osmosis has occurred, suggesting that the concentration of water inside the cell is equal to the solution outside. ...read more.

Conclusion

It would also mean that less experimental errors might occur as each job will not be as rushed. Using more types of molar sucrose solutions could give me a wider range of results which would then help me to make an easier conclusion whether the results complimented my predictions. Further work could be carried out to include concentrations that increased in 0.05 M. this would increase the accuracy and improve the graph other investigations could include using a different variety of potato and compare the results. Even different plant tissue could be used e.g. carrot, apple. I could change other key variables in the experiment not just the concentration e.g. the amount of time the plant tissue is left in the solution, the size of the plant tissue or perhaps the temperature that I do the experiment in could be varied. The size and shape of the plant tissue could be varied but I doubt whether this will have a substantial effect on the results. I think that temperature would be a good key variable to change, for example the samples could be placed in different water baths and brought up to different temperatures to see if temperature does affect the rate of osmosis. The same method could be applied to this as for the experiment I did except perhaps the plant tissues could remain in the water baths for 24 hours and then recordings could be done. Overall I think that with the apparatus and method which I used the experiment was a fairly good success. ...read more.

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