B 12MW Biology: Osmosis February 2008
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 (Ψ herein) to low water potential, through a semi permeable membrane. Using this movement of water you are able to determine the Ψ 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 Ψ 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. I know form prior work, investigation and study that the water potential will be around 0.4M. So I have decided to use 6 different solutions that are on either side of this figure. Table 1 below shows which molarity’s I will be using.
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Peer Reviews
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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.'
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.
Response to 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.