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Osmosis. Finding the water potential of potato tuber cells

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Finding the water potential of potato tuber cells "a cell is a city in disguise" - Copernicus Osmosis is the diffusion of water from an area of high water potential (? 1 herein) to low water potential, through a semi permeable membrane2. Using this movement of water you are able to determine the ? of a cell. And this is the basis of my coarse work as the aim is to: "Use your knowledge of osmosis and the table provided, to design an investigation to determine the water potential of potato tuber cells." I have already told you the definition of osmosis my using this movement of water I will be able to determine the ? of the tuber cells. I will be able to work it out by placing potatoes pieces into solution of different molarity of water and measuring the % change in mass. Choosing the molarity In the experiment I will have to make my own solutions from one cock stock sucrose solution. ...read more.


70cm3 distilled water : 30cm3 Sucrose stock solution 0.40 -1120 60cm3 distilled water : 40cm3 Sucrose stock solution 0.50 -1450 50cm3 distilled water : 50cm3 Sucrose stock solution 0.60 -1800 40cm3 distilled water : 60cm3 Sucrose stock solution By measuring the ratio of molarity to water potential (M:?). We are able to make solutions of the required molarity. For example if I wanted to make a sucrose solution of 0.4 moles. I would for every 6 measures of distilled water add 4 equal measure of 1 molar sucrose stock solution. So this would be a ration of 6:4. We can prove that it would be 0.4 moles per decimetre cubed. As by using the ration of 6:4 if I took 600cm3 of distilled water and mixed it with 400cm3 of 1 molar sucrose solution. I would have 400cm3 of 1 mole sucrose solution in 1000cm3 or 1dm3. So 400/1000 = 0.4 moles per dm3. Now that I have made the solution I am now able to perform the experiment that will allow me to work out the water potential in potato tuber cells. ...read more.


0.1M sucrose solution -260 0.68 0.71 0.71 0.76 0.77 0.75 0.2M sucrose solution -540 0.69 0.71 0.72 0.72 0.74 0.75 0.3M sucrose solution -860 0.70 0.71 0.71 0.69 0.69 0.68 0.4M sucrose solution -1120 0.71 0.69 0.76 0.69 0.62 0.64 0.5M sucrose solution -1450 0.77 0.77 0.77 0.61 0.60 0.56 0.6M sucrose solution -1800 0.66 0.67 0.67 0.53 0.59 0.60 Result Table My results will be put into this table, for later analysis. www.orzzz.com 1 ? is the symbol for water potential. Water potential works inversely as 0? is the highest ? you can attain, as it is a solution of water with no solutes in it (distilled water). A lower ? would be -12?. 2 Definition of osmosis from Advanced Subsidiary Biology - Heinemann Textbook 3 Given to us with this osmosis coursework 4 Please see table 2 for amount of sucrose needed for each solution 5 Please see table 2 for amount of distilled water needed for each solution ?? ?? ?? ?? B 12MW Biology: Osmosis February 2008 Barrow Hall College 1 ...read more.

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Response to the question

Basic essay. Introduction is good as it sets out the science behind the investigation and the theory. However, it does not submit a hypothesis which would have improved the investigation. Main body of the text basic, and no conclusion or ...

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Response to the question

Basic essay. Introduction is good as it sets out the science behind the investigation and the theory. However, it does not submit a hypothesis which would have improved the investigation. Main body of the text basic, and no conclusion or evaluation providing an incomplete response to the question. Responses are clearly set out.

Level of analysis

Use of tables which is good although tables could be better presented, and the osmolarity of the different moles of solution does not need to be presented. Does not consider any confounding factors that could be present and does not measure them which could also improve the experiment e.g. age of the potato used, and time out of water. Graph too small and hard to read. Random link at the end of text and no reference to where it belongs. No evaluation or conclusion reached from the results, and no consideration of potential bias and things that could be improved in the experiment. Level of analysis basic for the level I would expect from this candidate which only base knowledge used and no complex scientific terms.

Quality of writing

Grammar good in the most part apart from one or two sentences do not read clearly. Punctuation is okay apart from in the listing where it is sloppy and rushed, spelling is good for the most part, apart from in one or two instances such as the misspelling of 'from' with 'form.'

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Reviewed by skatealexia 15/03/2012

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