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The effect of temperature on the cell membranes of beetroot cells and amount of pigment released.

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Introduction

The effect of temperature on the cell membranes of beetroot cells and amount of pigment released. Apparatus * Corer size 4 * White tile * A Beetroot * Automatic Water Bath * Segregated knife * A thermometer * Stopwatch Method: * First take the white tile and the corer. Then collect a cylinder of beetroot by pushing the corer into the beetroot and withdrawing it. The cylinder remains inside the corer- so push it out with the end of a pencil. * Collect 3 cylinders, and then cut them into 6 pieces of 3 cm with a segregated knife. * The beetroot was cut to 1cm. Because the beetroot has been cut some of the cell membranes had been broken, which means some anthocyanin will leak out. This must be completely washed off in order to maintain the reliability of the results. * The water bath must then be heated to 20oC (the first temperature for the experiment) * Once the water bath is at the correct temperature (measured using the thermometer), one piece of beetroot is placed into the hot water directly and left for exactly1 minute (using a stopwatch). ...read more.

Middle

However when we increase the temperature the relatively weak forces holding the different parts of the polypeptide chains together (like hydrogen bonds, sulphur bridges and ionic bonds) can be disrupted very easily- this damages the vacuole and makes holes in the cell membrane, inducing leakage. The cell membrane is also damaged and so diffusion of betalain occurs through the partially permeable membrane by osmosis- the betalain molecules move by diffusion from an area where they are more highly concentrated to an area where they are at a lower concentration, along a concentration gradient. The reason why the amount of betalain pigment increases rapidly (from 40oC to 60oC) is because most mammalian protein's denature and tertiary structure unravels (the strong covalent bonds between the R groups of amino acids in the polypeptide chains are destroyed) at temperatures over 40oC. The reason why the curve starts to flattens out (between 60oC and 80oC), is because although the denaturing of the protein causes a rapid rise in the amount of betalain released to start with, when the temperatures begin to get higher still, the protein's tertiary structure blocks some of the holes in the cell membrane and therefore slows down the release of betalain. ...read more.

Conclusion

Another limitation was cutting the beetroot into pieces. The pieces cut had roughly the same surface area to volume ratio- but not exactly the same. This would have had a slight effect on my results because the rate of diffusion of betalain particles across the plasma membrane is increased, as the surface area of the beetroot increases. So the slightly thinner and smaller pieces of beetroot I cut would have released more betalain from their vacuole. I only looked at one type of plant cell, so I can not be sure that every plant cell and indeed eykaryote- which have different plasma membranes, that may be adapted to cope with heat better or worse than beetroot cells willl have the same results. I can firmly conclude that there are no apparent anomalies in my results and none of my sources of error or limitations of my experiment are enough to deem my results unreliable. However the sources of error and limitations in my results may have made my results slightly less accurate, but other students in my class found the same patterns occuring and roughly the same results- which would vary slightly between each beetroot anyway. ...read more.

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