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investigating how osmosis works against different concentrations of glucose

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INVESTIGATING HOW OSMOSIS WORKS AGAINST DIFFERENT CONCENTRATIONS OF GLUCOSE SOLUTION PLAN Aim The aim this investigation is to find at what point the water molecules stop moving and when the concentration of sugar and water molecules inside and outside the potato is equilibrium. Research Osmosis is a special kind of diffusion involving water molecules. It occurs when a partially permeable membrane separates two solutions, where water molecules move from a region high water concentration (weak solution) to a region of low water concentration (strong solution). Glucose rich solution will fill with water. Water acts like it is trying to dilute it, so as to 'even up' the concentration on either side of the membrane. Many water molecules (At beginning), fewer water molecules - Partially permeable membrane (The tiny holes in the membrane allow water molecules to pass through, but the Solute molecules are too big). Key: - Water molecules - Sugar molecules Solution before Solution after Weak Strong Solution solution Water in a dilute solution can move more freely than in a concentrated solution, because solute molecules attract water. (Water in any type of solution moves less freely than in pure water). Water molecules are more concentrated in weaker solutions than they are in stronger solutions. Turgor pressure Turgor pressure is when the cells contain as much pressure as it can hold and are blown up like a balloon. The cell walls stop the cell bursting and we say that the cell is turgid. This is useful as it gives the stem of plants support and it gives support to green plant tissues and stomatal guard cells. ...read more.


In addition I will ensure the test tubes are placed correctly in test tube racks so they do not roll of the desk and break. Lastly I will be very careful that the solutions don't get into the bodies internally as it could be harmful. Prediction When a potato is placed into a concentration of glucose solution, which is greater than a certain level the potato will contract. However if there is less glucose solution then the potato will expand. Therefore when a potato is placed in distilled water (high water concentration) water will move across the semi-permeable membrane in to the cell (lower water concentration) by the process osmosis, making the cell swell up. The cell will then be turgid. The potato cells increases in length, volume and mass because of extra water. If a potato were placed in glucose solution with low water concentration, then the opposite would happen. Water would move out of the cell in to the solution. In extreme cases the cell membrane breaks away from the cell wall and the cell is referred to as plasmosysed, the potato cells will have decreased in length, volume and mass. I predict that the potatoes with 4%, 5% and 6% glucose solution will go turgid. This is because the more hypotonic the concentration i.e. the lower the concentration of sugar the more water molecules will diffuse in to the cell through the semi permeable membranes making the potatoes swell up and will consequently, gain mass. I think water molecules will continue to move until the water concentration is the same on both sides of the membrane. ...read more.


I feel that I carried out my experiment reasonably, and I encountered no problems. As a result I ended up with a valid set of results. Further work Another experiment I could carry out to investigate osmosis would be to use a different fruit or vegetable. A potato contains lots carbohydrates in the form of starch, which is not soluble. A starch produces less osmotic pressure. If I used a fruit or vegetable that had sugar it would affect the osmotic balance, as lots of water would rush in to the cell making it very turgid. An apple could be an idea as it stores carbohydrates in the form of sugar (fructose). As a result I would expect the isotonic point would be much higher. I could use glucose solution from 6% up to 20%. I could then compare the results. If I used an apple I would expect the graph to look as follows: % Change in mass Apple Potato Concentration of glucose solution The same variables would apply for this experiment as those for my actual experiment. Also to ensure that the test was fair so reliable results were obtained I would have to use the same points for fair testing which I mentioned for this experiment. In addition safety would be just as important. I could use the same apparatus and idea of the method, which I used in my experiment. However one thing I could change would be to add the improvements I mentioned for this experiment. ?? ?? ?? ?? - 1 - ...read more.

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