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

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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. Therefore, the potato piece will stay the same size.

Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

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A cell can only become flaccid by losing water. The chain of events starts with water leaving the cell through the cell membrane by osmosis because the water concentration outside is lower than that in the cell. As water is lost the vacuole gets smaller as it is used to top the cytoplasm up. This reduces the volume of the cell contents so the membrane begins to shrink away from the cell wall. At first it will stay in contact with the wall at several points, but pretty soon it will shrink away from the wall completely. If the ...

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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.