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Water potential of potato tuber cells - the weighing method.

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Introduction

Water potential of potato tuber cells - the weighing method The Investigation of Osmosis The investigation was to find the differences in water molecules moving from an area of high concentration to an area of low concentration using potato tubes and varying the concentration of the solutions. The way in which water molecules do this is called osmosis. Osmosis is the movement of water through a semi-permeable cellulose wall and cell membrane along a water potential gradient. From previous research I predict that as the concentration of the solution outside the potato tubes is increased there will be a increase in the number of water molecules moving from the solution into the potato tubes, and also then as the concentration of the solution decreases there will be an increase in the number of water molecules moving from the potato tubes. Using this investigation we will also be able to work out the water potential of the potato tuber cells. Water potential is the potential that water molecules in a solution have of diffusing out of a cell as a result of their free energy. The symbol used to denote water potential is the Greek letter psi or ?. ...read more.

Middle

(Percentage change in mass = change in mass * 100 / original mass) 13) Graph the results by plotting the percentage change in mass against the molarity of the sucrose solution. A line of best ft should be drawn and ten where the line crosses the x-axis this is what the water potential of the potato tubers is. Water potential of potato tuber cells - the weighing method A table showing m results for different concentrations of sucrose solution on osmosis in potato tubers Concentration (M) Average Weight Before (g) Average Weight After (g) Increase/ Decrease Average Change In Mass (g) Average % Change In Mass (%) Distilled 1.12 1.24 Increase 0.12 +11 0.1M 0.81 0.85 Increase 0.04 +5 0.2M 0.93 0.96 Increase 0.03 +3 0.4M 0.88 0.72 Decrease -0.16 -18 0.6M 0.93 0.69 Decrease -0.24 -26 0.8M 1.09 0.68 Decrease -0.41 -38 Water potential of potato tuber cells - the weighing method Interpretation I recorded m data in an easy to read table along the top row I have given the name/heading for each column. Making it ea for a reader to quickly under stand what each column is about. I have then, down the left hand side, given the different concentrations and then in the middle of the table there are all the values, which correspond to the heading and the concentration. ...read more.

Conclusion

The molecular make up of each half of the membrane is different in that different lipids and proteins are more abundant in one side over the other. Proteins are a very important part of the cell membrane. Basically they can be classified into two groups based on physical distribution. Integral proteins are embedded within the cell membrane and may in fact pass multiple times through the membrane. Peripheral proteins are loosely associated with membrane surfaces. Carbohydrate portions of glycoproteins and glycolipids are found on the external surface of the cell membrane where they are important parts of receptor molecules. Receptors are necessary to cellular signalling, adhesion, and recognition. Most proteins are fixed in place within the cell membrane by interactions with the cytoskeleton. However, some integral proteins can move about and sometimes will accumulate on one region of the membrane in a process called capping. The cell membrane is not static. It is remodeled by the addition of new membrane vesicles from the Golgi while removal takes place in the form of endocytotic, phagocytotic and pinocytotic vesicles being formed and then fused with lysozomes for processing. Membrane receptors and membrane are often conserved and recycled to the plasma membrane. This membrane trafficking is important in the cell economy. Here is a diagram of the cell membrane: Osmosis will also occure in plant cells. Ryan Magee 13Q Biology Coursework AS Level ...read more.

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