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Investigate the effect on length when varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato pieces of the same size.

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Introduction

GCSE Biology Manish patalia Aim To investigate the effect on length when varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato pieces of the same size. And to find the water potential of potato pieces. Before I actually planning the experiment, I think that it is essential that I do some research about osmosis, and matters related to it, so that I an make predictions. And work out a way to make this investigation fair, safe and predictable. Planning my experiment will make it easier for me to know what to do and when. This will help me to get more accurate results. Hypothesis Diffusion is defined as the movement of water molecules across a partially permeable membrane from a region of high water concentration to area of low water concentration. This movement has to occur across a partially permeable membrane like a cell wall, which is penetrable by small molecules. Water as a small compound can easily diffuse through but larger molecules wont be able to penetrate the membrane. A partially permeable membrane is something that has tiny holes in it. So in fact only water molecules can pass through them and bigger molecules like glucose can't. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecule. A potato contains starch but it is not osmotically active (insoluble). This will affect the water potential of the cell's cytoplasm. In a partially permeable membrane like potato cells the water molecules can actually pass both ways through the membrane, like two way traffic. In some cases there may be some different amounts of water on each side of the membrane. For instance their may be more water outside the potato cells while a potato is placed in a jar of water. In this case because there is more water molecules on one side of membrane then the outside there's a steady net flow into the region with fewer water molecules, it into the stronger solution. ...read more.

Middle

Safety Even though this experiment doesn't use any dangerous chemicals its still vital that I and my fellow class mates follow safe procedures and never forget the importance of safety. Be carefully with the scalpel knife and do not run or walk with it. Use it accurately and softly to prevent miss control. Apparatus Potatoes Ruler Scalpel Various concentrations of glucose - 0 M/dm3, 0.1 M/dm3, 0.2 M/dm3, 0.3 M/dm3, 0.4 M/dm3, 0.5 M/dm3, 1.0 M/dm3. Distilled water Petri Dishes Stopwatch Plan of Method The practical part of this investigation is very easy and merely time consuming 1) Firstly I will make a template from a potato. I will cut the potato up into many slices which are 1 cm thick. With them slices I will use a ruler and a scalpel knife to cut out a template potato which I will use to cut out the other potato pieces from the potato slices. I will make sure that piece is 2cm x 1 cm x 1cm 1cm (not drawn to scale) 2cm 2) I will then measure each potato piece with a metal ruler with the sub multiple of the centimeter which is the millimeters. 3) I will make sure that all the potato pieces measure 2x1x1cm. 4) I will then place the 21 pieces into 21 different petri dishes. i will make sure the Petri dishes have been cleaned of any dirt or any impurities that may effect my results. 5) I will then make pour the sucrose solution in all of the pieces. I will pour 7cm3 of the molar solutions in all the Petri dishes. Each molar level solution will be tested on three potatoes so I get the most accurate of results. 6) When the 7cm3 of solution is placed in every single Petri dish I will place the lids on the solution to prevent evaporation and I will place the dishes in sunlight which will sustain the rate of osmosis. ...read more.

Conclusion

The cells of the chips became plasmolysed and therefore the chips become soft because the cells had lost water. The reason that there is a decrease in length of the potato pieces is because there is a higher water potential outside the potato pieces and its cells. I overall conclude that my predictions were correct and that my results are strong enough to prove my predictions. Evalutation Aim - To determine the water potential (?) of a potato. My experiment went according to plan, I had no anomalous results and my implementation of my method went according to plan. I followed all the fair test procedures to insure that my results were accurate. Even though my results were conclusive and accurate I do think the whole experiment could have been improved to obtain better results. If the potato pieces came from the same place and they were cut with a machine to insure that they were perfectly identical in size and volume, then I could of obtained more conclusive results. Some of my potato pieces had slight grooves on them altering the size of the surface area which would inevitably effect osmosis and my results. As I said in my conclusion my results directly correlated into my trend and proved my predictions correct. If I were to change the experiment and find out any other factors which effect osmosis I would change the size and surface area of the potato pieces and see the effect that it has on osmosis. I would also change the time I let osmosis occur from 20 minutes to one hour. I would do this because osmosis would occur to a better and more fulfilled degree. I could also analyze the effect of temperature on osmosis. I would change the factors above if I was to further extend my investigation. I would also use molar solutions that were more consistent in there concentration as I jumped four molar levels in my experiment 0.6, 0.7, 0.8, 0.9 were all left out. I could also use different types of plant, like specially adapted plants for instance. ...read more.

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