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How does the concentration of salt solution affect osmosis in potatoes?

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Introduction

Year 10 coursework - Osmosis How does the concentration of salt solution affect osmosis in potatoes? Introduction Osmosis is movement of water through a selectively permeable membrane, from where there is a higher water concentration (or water potential) to where the water concentration is lower. In this piece of coursework I will answer the question, 'How does the concentration of salt solution affect osmosis in potatoes?'. If you put a piece of potato into pure water, the water concentration is obviously higher outside the potato. Therefore water moves into the potato by osmosis. This will cause the potato piece to swell. However, if you put a piece of potato into a strong salt solution (where the water concentration is low), then water will move out of the potato. The potato piece will therefore shrink. If a salt solution has exactly the same water concentration as the potato piece, then it is likely that there will be no overall movement of water in or out of the potato. ...read more.

Middle

If you put a plant cell in water, water enters by Osmosis, then swells up. However, the cell will not burst. This is due to the fact that the cell walls are made from cellulose, which is extremely strong. Eventually, the cell stops swelling, and when this point is reached, we say the cell is turgid. This is important, because it makes plant stems strong and upright. The experiment I will do is to find the water potential of a potato, by putting potato pieces into different solutions of salt of known concentrations, until I find the concentration where the potato piece stays the same size. To make this experiment a fair test, I would need to keep everything else constant as far as possible. For example, I need potato pieces of the same size, and should always use the same volumes of salt solutions. Prediction I predict, that as concentration increases, the weight and length of the potato chip will decrease. ...read more.

Conclusion

Relating this to the potato chips: basically, as the concentration of salt in each solution increases, the water in that solution is less able to move to the potato, causing water from the potato to move to the solution, decreasing its length, weight and width. Osmosis is established when a semi-permeable membrane is placed beween two solutions. In biological systems osmosis is the exchange of water between the toplasm and the surrounding medium, with the plasm membrane being the semi- permeable membrane. An example of this in my results is the test at 1 molar. In other words, it becomes dehydrated and loses water through plasmolysis. If the concentration of the salt solution (in our case Glucose solution) outside the cell is less than that inside the cell, this means that the solution is Hypotonic to the cells of the potato chip. The water will diffuse into the cells, making it turgid. This would explain why potato chips put into a solution of 0 molar seemed very firm compared to the potato chip used for 1 molar, this was because the cells of the potato had lost their turgor, and had become flaccid. ...read more.

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A very clear account showing a detailed understanding of osmosis written using a good standard of GCSE level biological terminology. Better coverage of variables needed for 5 stars.

Marked by teacher Adam Roberts 10/05/2013

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