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Osmosis in a Potato Chip.

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Osmosis in a Potato Chip Plan Hypothesis I think that the potato chips once immersed into a solution with a higher concentration of sucrose will lose weight through water leaving the cell by osmosis. I believe from my past knowledge of a similar experiment involving visking tubing and an investigation into chemical digestion and absorption that osmosis will occur across a selectively permeable membrane down a concentration gradient. Therefore once the potato chip is immersed in distilled water (a hyperosmotic solution) water will diffuse into the potato by osmosis causing a weight gain until the cells are turgid. Prediction Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution to a more concentrated one (i.e. down the concentration gradient). The selectively permeable membrane only allows molecules smaller than a certain size pass through them hence the name. The cell membrane in a potato will only allow water molecules to pass freely through them as they are relatively small however it will not let a sucrose molecule pass through it due to its size. If on one side of the membrane there is a higher concentration of sucrose molecules (i.e. a smaller concentration of water) water molecules will diffuse through the selectively permeable membrane to reduce the concentration of sucrose molecules. This is so that the concentration of water on either side of the membrane is equal and an equilibrium has been reached. From my past knowledge involving red blood cells being immersed in a hyperosmotic solution (distilled water), water diffused by osmosis into the red blood cells from an area of high concentration of water down the concentration gradient. This resulted in the red blood cells absorbing too much water due to them only having a slightly elastic cell membrane. However, in a potato chip, if immersed in distilled water, will increase in weight by absorbing distilled water by osmosis due to their being a lower concentration of water inside the cell vacuole. ...read more.


This can be easily controlled by cutting them off with a scalpel. Safety I will need to ensure that my experiment is safe, I can do this by taking care when I use the scalpel when cutting the potato, care will also be taken how I hold the potato when using the cork cutter in case it goes straight through the potato. I will also take care with the glassware that I use e.g. test tubes so that breakages will not occur. This can also be avoided by being as organised as possible and only having the necessary equipment on my desk at one time. Lab coats will be worn to avoid spillage of fluids and especially the sucrose solution, as this is very sticky on to my clothes. I shall also be careful and aware of other people's actions and experiments. Analysis From my table of results and the graph that I have drawn from my results I can conclude that my prediction was correct. The potato chip did in fact gain weight when immersed in a distilled solution and it also lost weight when immersed in a solution of sucrose as stated in my prediction. These results can be easily explained by having an understanding of osmosis. The potato chip gained weight when immersed in distilled water because water molecules diffused into the chip by osmosis across the cell membrane thus causing a weight gain. The water diffused across the cell membrane because there was a higher concentration of sucrose and salt molecules (i.e. lower concentration of water) inside the cell than the water outside the cell creating a concentration gradient. This caused the water molecules to move into the cell to equal out the concentration of water and to reach equilibrium. This intake of water would have caused the cell vacuoles to expand in size exerting pressure on the cell membrane and consequently making it stretch until it reached the cell wall and became fully turgid. ...read more.


There was also an error in the weighing of the potato after the experiment because of excess sucrose solution on the potato after being withdrawn from the solution. I tried to eliminate this by leaving the chip on some paper towel however this may have taken too much water off the potato thus affecting the mass. I was also lucky enough not to get any anomalous results I think I can put that down to the accuracy of the procedure and also the use of using repeats. This would prove the results were more reliable and anomalous results would become more apparent. There was also a time delay in some potatoes coming out of the solutions, therefore some would come spend a longer time in the solution than they were meant to. This would have resulted in a larger weight change. This could have been avoided by starting the experiment for different concentrations at different times. However this would not have been practical due to time limitations. If I were to perform this experiment again I would make a few changes and improvements to improve my results and also to increase my investigation. To increase and widen my investigation I would use a different variable or increase to the measurements I took. For example I would have liked to measure the length of the chip after the experiment to see if an increase in size or plasmolysis had occurred. I would also use a different variable for example changing the water temperature this would increase the rate of osmosis and therefore the speed of the water molecules. I would also try to increase the accuracy and reliability of my results by investigating more than one potato, taking more repeats. I would also start my experiments at different times to stop there being a rush at the end. I would also use larger potatoes so that a larger variation in the change in weight could be obtained. Royce Peever Biology Coursework ...read more.

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