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Experiment Aim: To investigate the effects of placing onion epidermal cells in different solutions.

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Introduction

Title: Cell Structure Aim: To investigate the effects of placing onion epidermal cells in different solutions. Apparatus: onion, methylene blue solution, distilled water, petri dish, 0.6 and 0.1 moldm-3 sucrose solution, microscope slides, light microscope, razor blade, knife. Method: A piece of the inner epidermis was removed from an onion scale. Two pieces of the epidermis were cut about 5mm*5mm. the pieces were placed in a small dish covered with methylene blue solution and put aside for 5 minutes. After 5 minutes the pieces of epidermis were removed and washed carefully in a dish. One piece of tissue was mounted in 0.6 moldm-3 sucrose solution on a microscope slide under a cover slip. The slide was then labeled. ...read more.

Middle

0.15 0.45 0.40 0.05 5 0.40 0.28 0.12 0.25 0.21 0.04 Discussion: Osmosis is the movement of water molecules down their diffusion gradient, through a partially permeable membrane. When placed in solution water molecules will enter or leave a plant cell through osmosis depending on water potential. The water potential is the tendency for water to a solution. It diffuses out a dilute solution (a lot of water- high water potential) and into concentrated solution ( a lot of solute- low water potential). When a plant cell is placed into a dilute solution which has a greater water potential than it, water enter the cell by osmosis. The cell wall of the plant cell does not directly affect this movement, because it is fully permeable to water and to most of the solute in it. ...read more.

Conclusion

Using the measurements of the dimensions A and B the extent of plasmolysis by each concentration was obtained. This showed how far the contents of the cell moved from the cell wall. A greater extent of plasmolysis occurred in the 1.0 moldm-3 solution than the 0.6 moldm-3 whcich meant it has a greater water potential. More water therefore left the cell in the 1.0 moldm-3 solution than the 0.6 moldm-3. The procedure could have been extended by observing more cells and also by keeping the tissue in longer in the concentrated solution. Conclusion: It can be concluded that the cells in the 1.0 moldm-3 sucrose solution lost more water and therefore became more plasmolysed than the cells in the 0.6 moldm-3 solution. Hence the higher the concentration the greater the extent of plasmolysis in the cells. ...read more.

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