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Osmosis Experiment.

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Introduction

Liam Tai-Hogan Biology Coursework Osmosis Experiment Osmosis: is when a substance such as sugar dissolves in water, the sugar dissolves in water, and the sugar molecules attract some of water molecules and stop them moving freely. This, in effect, reduces the concentration of water molecules. There are more free water molecules on the left of the membrane than on the right, so water will diffuse more rapidly from left to right across the membrane than from right to left. Osmosis is water passing from a region where it is highly concentrated to a region where its concentration is lower, through a partially permeable membrane. Below is a basic diagram of Osmosis. Definitions: (from www.studentcentral.com) A Partially Permeable Membrane allows the free passage of some particles but is not freely permeable to others. Biological membranes are freely permeable to water but have restricted permeability to solutes such as glucose molecules, i.e. they are selectively permeable. Hypotonic Solution A Hypotonic solution is where there is a lower concentration on the outside off the cell than on the inside of the cell. Isotonic Solution An Isotonic solution is when the concentration on the inside is exactly the same as the concentration on the outside. Turgidity A plant is said to be turgid when they become too big but they still continue to take in water, as the concentration inside the cell is lower than the concentration on the outside of the cell. ...read more.

Middle

3. The vacuole shrinks, pulling the cytoplasm away from the cell wall, leaving the cell flaccid. To find the percentage change in my results I will use this equation. Percentage Change = Change Initial X 100 Results: Note: The original average weight' was after made 10 the pieces were weighed and an average was made. The 'length after experiment' and 'weight after experiment' were made by making an average out of the two pieces of potato. Length Concentration (ml) Original Length (cm) Weight after experiment (cm) Percentage Change% Turgid? 50 water/ 0 sucrose 5 5.55 11 Very 40 water/ 10 sucrose 5 5.05 1 Same 30 water/ 20 sucrose 5 4.5 -10 Loss of turgidity 20 water/ 10 sucrose 5 4.25 -15 Thinner and loss of turgidity 10 water/ 40 sucrose 5 4.08 -18.4 Very Thin and more loss of turgidity 0 water/ 50 sucrose 5 3.95 -21 Even thinner and greater loss of turgidity Weight Concentration (ml) Original Weight (g) Weight after experiment (g) Percentage Change% Turgid? 50 water/ 0 sucrose 1.80 2.15 19.4 Very 40 water/ 10 sucrose 1.80 1.85 2.7 Same 30 water/ 20 sucrose 1.80 1.61 -10.6 Loss of turgidity 20 water/ 10 sucrose 1.80 1.23 -31.6 Thinner and loss of turgidity 10 water/ 40 sucrose 1.80 0.92 -48.9 Very Thin and more loss of turgidity 0 water/ 50 sucrose 1.80 0.78 -56.7 Even thinner ...read more.

Conclusion

This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what make the green parts of the plant "stand up" into the sunlight. Although this is not a necessary feature in potatoes, they are still plant cells and they have basically the same properties as a plant cell from the leaf of a regular plant. Although I think my experiment went well I would like to make the following changes if I were to do it again. If I were to do the experiment again, I would like to create over three sets of results, each one in a different container. I would also like to leave the solution for longer to see whether it affected the percentage change and the difference between the percentage changes. The other thing I would like to do would be to use at least double the number of types of concentration, I would like to see whether than graph completely levels out at the end, this would mean the cells were completely flaccid and Plasmolysis had occurred. One point in my results that I think is wrong is the measurement of weight for the concentration- 20ml water/30ml sucrose. This can clearly be seen on my graph, as it does not fit in along the line of best fit. By doing the corrections to my experiment as above, I believe the line of best fit would be a better curve. Possibly ...read more.

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