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Osmosis in potato and apple

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Introduction

Investigating The Effect Of Osmosis On Two Different Plant Tissues The aim of the investigation is to find out the effect water potential has on osmosis in two different plant tissue; apple and potato. To help me on this investigation I decided to conduct a preliminary experiment. This allowed me to have an overall impression of the experiment, and I could spot any weaknesses in my experiment which I can modify to ensure that the real experiment has no flaws, so that the result obtained are accurate and reliable. The preliminary experiment involved cutting five 'chips' of each tissue sample, to equal size, and placing each into different concentrations of salt solutions. After an hour, the samples were taken out of the solution and measured. The results and graph are in appendix 1. Possible variables There are a number of factors I shall be keeping the same: 1 Temperature: the temperature must be kept constant throughout the experiment as it may affect the results, and the movement of water molecules. 2 Volume of salt solution: the volume must be kept the same; in this experiment, each 'chip' will be immersed in 40ml of salt solution. ...read more.

Middle

At this point the cell is said to be fully turgid. In whole plants it is the turgidity of their cells that helps hold them upright and spreads the leaves out to the sun so that they can photosynthesise efficiently. If plant tissue is placed in a solution of lower water potential than its own, the process described above will occur in reverse; the net movement of water molecules will be into the surrounding solution and the cell will become increasingly flaccid as pressure exerted by the membrane on the cell wall decreases. If this process continues, the membrane will start to pull away from the cell wall as the contents of the cell are steadily depleted. This process is known as plasmolysis. If plant tissue is placed in a solution with a water potential that is equals to its own, water molecules will still move between the external solution and the contents of the cell, but the system will be at equilibrium as the net movements into and out of the cell will be the same. The cell will therefore neither swell up nor shrink. ...read more.

Conclusion

After one hour has passed for the chips placed in distilled water, remove them, dry them carefully and measure the length and mass. Record it in the table. 5. After one hour has passed for the other chips in each concentration, remove them, dry them carefully and measure. Repeat steps 1 -5 with the potato. Plant tissue Concentration of Salt Solution Initial Length (mm) Final Length (mm) Difference in Length % Change Initial mass (g) Final mass (g) Difference in mass % Change in mass Potato 0 0 0 0 0 Total Average 0.2 0.2 0.2 0.2 0.2 Total Average 0.4 0.4 0.4 0.4 0.4 Total Average 0.6 0.6 0.6 0.6 0.6 Total Average 0.8 0.8 0.8 0.8 0.8 Total Average 1.0 1.0 1.0 1.0 1.0 Total Average Plant tissue Concentration of Salt Solution Initial Length (mm) Final Length (mm) Difference in Length % Change Initial mass (g) Final mass (g) Difference in mass % Change in mass Apple 0 0 0 0 0 Total Average 0.2 0.2 0.2 0.2 0.2 Total Average 0.4 0.4 0.4 0.4 0.4 Total Average 0.6 0.6 0.6 0.6 0.6 Total Average 0.8 0.8 0.8 0.8 0.8 Total Average 1.0 1.0 1.0 1.0 1.0 Total Average ...read more.

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Response to the question

This piece of coursework lays out the experiment incredibly well, including a preliminary experiment and a hypothesis, but it was a shame not to see any analysis of the final results. Without an inclusion of the results, a graph and ...

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Response to the question

This piece of coursework lays out the experiment incredibly well, including a preliminary experiment and a hypothesis, but it was a shame not to see any analysis of the final results. Without an inclusion of the results, a graph and some relevant analysis, this essay doesn't directly answer the question. If this was available, this piece would be a very strong example of an investigation.

Level of analysis

This essay is able to pick out the variables which could affect the investigation, posing a solution to keep them controlled. It is made clear that the controlled variable is the concentration of salt solution. Terms regarding precision and reliability are used well, but validity is not mentioned. Validity could've been mentioned if the essay had analysed the results, comparing the outcomes with their hypotheses. The scientific terms when describing osmosis are strong, including water potential and partially permeable membrane.

Quality of writing

This piece is written coherently and uses technical terms throughout. One query is that the first person is used throughout: a more sophisticated piece would be able to write fluently without saying "I decided to". Tables were used well to support the investigation, and diagrams aided in explaining osmosis. This was a very well thought out piece of work, so it was a shame not to see any post-experiment analysis!


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Reviewed by groat 06/02/2012

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