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Investigate the cell sap concentration of solute in a potato chip using osmosis and produce a figure informed by the investigation as to what this is.

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Aim The aim of the experiment is to investigate the cell sap concentration of solute in a potato chip using osmosis and produce a figure informed by the investigation as to what this is. Background Information A factor that effects how much water moves into a cell is the solute concentration within it. Water moves in and out of cells by diffusion, this diffusion is called osmosis. Osmosis is the diffusion of water molecules from a place with a high water potential or high concentration of water to a low water potential or low concentration of water. If a solution has a high water potential this means it is weak or dilute solution so it only has a small solute (e.g. glucose) concentration. However, if a solution has a low water potential it is a strong more concentrated solution because it has a much higher solute concentration. Osmosis is the diffusion of water in these solutions from a high water potential to a low water potential or in terms of solute concentrations, from a dilute solution to a more concentrated solution as a more concentrated solution would have a much lower water potential that a dilute one. The water passes through what is known as a partially permeable membrane, which basically is what separates living cells from their surrounding. The membrane is called partially permeable and not fully permeable because it only allows water to diffuse through it and not solute. The cell wall is an example of a fully permeable membrane because it allows water and solute to pass through it, it does not block any of these molecules. The diffusion of water molecules by osmosis always flows down a water potential gradient, which basically means from a high to a low water potential this is how the water moves up through a plant in the xylem vessels, once one cell is full of water, the water will move all at once to the next cell. ...read more.


The solutions were stirred well so that the sugar would dissolve in the water and not just settle at the bottom. The intervals of the % solute variable were all even which meant it was much easier to measure and therefore fairer as less random errors would occur when measuring. Safety was not much of a hazard in this experiment because it did not involve hot or toxic materials, however, care was taken when using the knife, beakers and tweezers and a tile was used when cutting as to not damage the wooded desk. Analysis The graph shows a good negative correlation and all the results follow a basic trend near or close to the line of best fit. An average of all the results was calculated after the graph was drawn, it helps to support the graphs correlation as the average actually lies right on the line of best fit. On the graph the point at which there is no net movement of water in or out of the chips is 6%; this result supports the prediction that was estimated at between 0% and 10% yet not the two extremes. The graph also helps to explain what is happening to the cells in solutions that are different from 6%. For example at 0% concentration the graph show that the chips gained in weight by an average of 10.4%, this means that water had entered the cells so their mass had increased. Water must have entered the cells because the solute concentrations in the chips were larger than the solute concentration outside of the chips. They would have had a lower water potential due to the fact that they had more solute in them so the water would flow by osmosis (diagram 1) down the water potential gradient and into the cells of the chips in this case. At 5% solute concentration the chips also gained in weight yet not as much as they did at 0%, they gained in weight for the same ...read more.


Likewise the duration could be increased to see the point of implosion when the cells can't get any more plasmolysed and they have lost all the water they contain and shrank due to a decrease in turgor pressure. It would be helpful to do an experiment with the temperature of the water higher to see if this effects the change in mass at the solutes, maybe make more water enter with the dilute solutions and cause more to be lost in the strong solutions. It would also be interesting to see if water temperature has any affect on the % concentration when there is no net movement of water between the cells and the solution. It would also be good to test the chips from different parts of the potato as they may have different solute concentration and it may be discovered that the point of no net movement will be different in different areas of the potato or even in different areas of the same chip. The smaller the potato slices from the different areas of the potato then the more detailed an analysis could be of which part of the potato has the highest/lowest % solute concentration. The experiment could be done again using smaller concentrations, say with a range of 5%-7% and at intervals of 0.25% this way a figure for the actual % solute concentration in a potato chip could be pin-pointed to a much more exact figure. Finally an experiment could be done using different types of potatoes to decipher whether the type of potato depends on the % solute concentration it has. The trends could be taken for many types of potato and then an average taken of them to give a figure which most represents the solute concentrations in many potatoes. This figure could then be compared or even investigated at the same time as an experiment to see if there were different solute concentrations in different parts of the potato and the links, if any, between them analysed. By Charlotte Swain - 10 Separate Science ...read more.

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