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Investigate the water potential of beetroot tissue using experiments and your own knowledge.

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Introduction

Richard Eatock 12J Biology Coursework Aim: Investigate the water potential of beetroot tissue using experiments and your own knowledge. Background Information Definition - "the net movement of water molecules from a region of higher water potential to a region of lower water potential along the concentration gradient across a semi-permeable membrane..." Osmosis is a very special example of diffusion. It is the movement of liquid molecules across or through a barrier. An example might be the uptake of water by the roots of a plant. The water moves across the barrier if there is less water on the other side, i.e. if there is less water in the root cells than in the soil. The water enters the plant root cells by crossing the cell wall. The membrane inside the cell wall is an example of a semi-permeable membrane. This means that it will allow certain molecules to pass through it but not others. It acts rather like a filter. Water and minerals are small enough to pass through the plant's membranes. This process is essential for the survival of the plant. Many membranes allow all or none of the particles of a solution to pass through, only a few allow this selective flow. ...read more.

Middle

* The strength of the solution in the test tube * The amount of time the potato was left in the test tube. The variable that I have decided to vary is the strength of the solution in the beaker. This will enable me to determine the water potential. All the other possible variables will be kept constant to make each experiment fair and to enable me to get accurate results recorded. Fair Test: * All twenty-one beetroot cylinders must all be taken from the same beetroot. * Separate test tubes and measuring cylinders must be used for each solution, this is to avoid any contamination. * Must be a new piece of Toilet Tissue used to dry each beetroot sample and the samples must be dried lightly and not squashed. * The same volume of solution must be used per concentration. * The beetroot cylinders must be trimmed to the same length. Safety Points * Be careful especially with the knives when cutting the beetroot. * Be aware of other people around you. * Make sure you are clear on what you are doing. * Don't play with the equipment especially in a science lab. Equipment * One whole Beetroot * 5mm Cork-borer. * Seven beakers. * Timer. ...read more.

Conclusion

And so, by using this table of Water Potentials and Sucrose Solution Concentrations we can discover the Water Potential of the beetroot: Concentration of sucrose (M) Water Potential (kPm) 0.90 -3010 0.95 -3250 1.00 -3510 1.42 -5800 (approx.) 1.50 -6670 2.00 -11810 The water potential of beetroot is approximately -5800 kPm. Evaluation I am reasonably pleased with the outcome of this experiment as I feel that I have obtained some reliable and fairly consistent results. I think that measuring the volume of solution left in the containers after the experiment has taken place would be of great benefit as it would give me more data to draw results from and better conclusions could be drawn. Another idea that could be implemented would be to repeat the experiment more times as then more data is used and more accurate averages can be obtained. An alternative route that could be taken is to calculate the beetroots surface area for each sample which could lead to varying the surface area and seeing just how much difference that it makes. Information used from "Biology 1" by Mary Jones, Richard Fosbery and Dennis Taylor "Biology 2" by D.J Taylor, N.P.O Green, G.W Stout The Internet (www.ocr.org.uk) (www.homeworkhigh.com) "Advanced Biology" by J. Simpkins and J. Williams Encarta encyclopaedia ...read more.

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