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Factor affecting osmosis in plant cells.

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Introduction

Biology Coursework - Factor affecting osmosis in plant cells Introduction Osmosis is the passage of water molecules from a weaker solution into a stronger solution through a partially permeable membrane. Plant cells are surrounded by a cell wall. This is fully permeable, which means it will not let any molecules go through it, so osmosis will not occur across it. A plant cell also has a cell membrane just like an animal cell. The cell membrane is selectively permeable in the same way as an animal cell. As the water goes in the cytoplasm and vacuole will swell. However, the plant cell has a very strong cell wall around it. The cell wall is much stronger than the cell membrane and it stops the plant cell from bursting. The cytoplasm presses out against the cell wall, but the cell wall resists and presses back on the contents Prediction I predict that the piece of potato in the highest concentration of sucrose will lose weight or gain the least. The piece of potato in the lowest concentration of sucrose will gain the most. I predict this because the water molecules move from a weaker solution into a stronger solution. The water molecules will pass through the partially permeable wall of the potato and into the potato. e.g. 20% sucrose = 4.7g > 4.72g 0% sucrose = 4.7g > 5.02g Planning In my experiment I am going to keep the volume of the solution the same and the weight and mass of the potato the same. ...read more.

Middle

Change in mass (g) % change in mass 1 20 4.70 4.45 -0.35 -5.3% 2 15 4.78 4.98 0.2 4.2% 3 10 4.69 4.94 0.25 5.3% 4 5 4.72 4.89 0.17 3.6% 5 3 4.75 4.90 0.15 3.19% 6 1 4.68 4.79 0.11 4.4% 7 0 4.71 5.03 0.32 6.8% Experiment 2 Test Tube no. % Concentration of sucrose Mass of potato before (g) Mass of potato after (g) Change in mass (g) % change in mass 1 20 4.17 4.29 0.12 2.9% 2 15 4.03 4.15 0.12 3% 3 10 4.11 4.21 0.10 2.4% 4 5 4.15 4.19 0.04 1% 5 3 3.42 3.6 0.18 5.3% 6 1 4.19 4.32 0.13 3.1% 7 0 4.18 4.31 0.13 3.1% Experiment 3 Test Tube no. % Concentration of sucrose Mass of potato before (g) Mass of potato after (g) Change in mass (g) % change in mass 1 20 5.54 5.75 0.21 3.8% 2 15 5.56 5.58 0.02 0.4% 3 10 5.52 5.56 0.04 0.7% 4 5 5.6 5.64 0.04 0.7% 5 3 5.56 5.67 0.11 2% 6 1 5.63 5.79 0.16 2.8% 7 0 5.66 5.77 0.11 1.9% Experiment 4 Test Tube no. % Concentration of sucrose Mass of potato before (g) Mass of potato after (g) Change in mass (g) % change in mass 1 20 3.05 3.31 0.24 8.5% 2 15 3.03 3.28 0.21 8.2% 3 10 2.98 3.28 0.3 10% 4 5 3.01 3.34 0.33 11% 5 3 ...read more.

Conclusion

They move in osmosis, which is the passage of water molecules from a weaker solution to a stronger solution. They move from the weaker sucrose solution into the stronger solution of the potato. Evaluation My experiment went quite well but I could improve it. In my experiment the results were quite accurate. I only got one anomalous result and three, which were slightly off the line of best fit. I could of improved my experiment by using the same sized cork borer for all the experiment because once I had to use a smaller one. I could have spent more time trying to get the potatoes more the same size but we where slightly short of time. If I would have had more time I also would have left the potato in the solution for longer e.g. 1 hour. I also would have got a potato with a higher dry matter e.g. a maris piper and I could have put clear labels on the test tubes to prevent them from getting mixed up. My results where very reliable I think because I did the experiment four times and got roughly the same results. If someone where to repeat the experiment they would get roughly the same results that I got. I could do further research by maybe testing out some other vegetables which grow under ground like a potato and test osmosis again with them. I would test them in about the same way as I did with the potato. Heather Bibby ...read more.

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Here's what a teacher thought of this essay

3 star(s)

In this report on an investigation into the effect of sucrose concentration on percentage mass change in potato tissue, the writer follows the standard GCSE structure for practical write-ups covering all the main sections, albeit not always in sufficient detail.

[1] The introduction was a little brief and could have described work carried out by other scientists on the same topic.

[2] The method lacked detail with regard to numerical values (times, volumes, concentrations) but was otherwise clear and appropriate.

[3] The results were quite bizarre with the four replicates generating very different data with no obvious trends.

[4] Unfortunately, the student did not analyse this data in a realistic way, choosing to ignore the lack of consistency (and reliability).

However, although the quality of the data collected is poor, the student makes a fair attempt at writing up the work and with the improvements listed above, would gain a middle grade at GCSE.

3 stars

Marked by teacher Ross Robertson 10/05/2013

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