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An investigation into the osmotic properties of a kumara (sweet potato)

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Introduction

An investigation into the osmotic properties of a kumara (sweet potato) Aim The aim of my experiment is to find the water potential of the kumara or sweet potato by investigating the osmotic properties and hence come to a conclusion of the exact water potential. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. Semi-permeable membranes are very thin layers of material (cell membranes are semi-permeable) which allow some things to pass through them but prevent other things from passing through. These things pass through tiny pores in the semi-permeable membrane. Cell membranes will allow small molecules like oxygen, water, carbon dioxide, ammonia, glucose, amino-acids, etc. to pass through. Cell membranes will not allow larger molecules like sucrose, starch, protein, etc. to pass through. Cells walls found in plant cells are fully permeable. A region of high concentration of water is either a very dilute solution of something like sucrose or pure water. A region of low concentration of water is a concentrated solution of something like sucrose. ...read more.

Middle

If you put plant cells into concentrated sugar solutions and look at them under a microscope you would see that the contents of the cells have shrunk and pulled away from the cell wall: they are said to be plasmolysed. When plant cells are placed in a solution which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. "Incipient" means "about to be". When I forget to water the potted plants in my study you will see their leaves droop. Although their cells are not plasmolsysed, they are not turgid and so they do not hold the leaves up into the sunlight. Apparatus: * McCartney bottles * Stopwatch * Scalpel * Cork borer * Sucrose solution 2Molar concentration * Kumara (sweet potato) * Filter paper * Weighing scales * Syringe Variables The variables in this experiment are: size, temperature, volume of solution, surface area of kumara, concentration, maturity of kumara and pressure. The variable I will change is the concentration of the sucrose solution. Results Before (g) ...read more.

Conclusion

I cannot see an anomaly, this is most probably as the experiment was comprised of 3 sub experiments giving a fair and accurate average. An anomaly could also have been the result of the Kumara being changed at that point so the molar of sucrose in the new Kumara could have been different. The results give enough evidence to let me conclude that the Kumara gains weight in low molar sucrose solution because I know that that the kumara has a high sugar content and that using osmosis the water in the sucrose solution will diffuse from an area of high concentration to an area of low concentration. To improve the experiment I could try to do the whole experiment with the same kumara and weigh them more accurately. To further the investigation I could use potatoes or another fruit and compare those results to that of the Kumara and in doing so find out which has the highest sugar content and water potential. ?? ?? ?? ?? William Biggs Biology coursework Investigating the osmotic properties off a kumara ...read more.

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