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An investigation into the amount of gas produced by a solution of glucose and yeast.

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Biology Coursework: An investigation into the amount of gas produced by a solution of glucose and yeast. Results % Glucose Concentration vol gas (mm3) 0 1 2 4 6 10 0 0 0 0 0 0 0 30 15 10 18 8 15 60 10 13 27 6 10 90 5 12 13 14 10 120 5 15 17 11 12 150 7 20 19 11 16 180 4 18 18 17 15 210 5 22 18 16 18 240 2 15 20 15 16 270 3 15 17 15 12 300 1 15 18 17 5 330 5 5 17 18 5 360 2 5 13 13 5 390 1 5 15 15 9 420 2 3 15 17 2 450 3 5 17 12 9 480 2 2 15 13 12 510 1 3 6 18 12 540 2 3 9 12 9 570 2 4 5 12 9 600 0 1 12 11 8 630 2 4 0 10 6 660 2 2 0 12 9 690 2 3 9 10 13 720 0 2 5 5 11 750 2 3 4 7 6 780 2 1 1 12 3 810 2 3 0 6 9 840 2 1 0 10 6 870 2 3 0 0 4 900 2 2 0 7 ...read more.


Alcohol would also be produced, but the reaction for anaerobic respiration, C6H12O6 --> 2C2H5OH + 2CO2 tells me that for every mole of glucose, two moles of alcohol would be produced, and thus a 1% solution of glucose would produce a 2% solution of alcohol when fermentation is complete, but this is only if the solutions are measured by moles, and in this case, I don't think it is safe to assume that this is so. Therefore, I cannot include this quantitative theory in my explanation. However, I could possibly work out if alcohol was ever a limiting factor by looking at the results; the four percent solution slowed down and basically stopped producing gas towards the end of the experiment. The fact that it stopped producing gas before it had produced double the amount of gas that the two percent solution produced shows that there must have been some limiting factor other than the yeast using up all the glucose. It could not have been that the cells had become plasmolised, because this would have had a much greater effect at the beginning of the experiment when the glucose concentration was higher. Therefore, I suggest that the factor that limited the four percent solution from producing more gas was that the alcohol levels had reached a level high enough to denature the enzymes and kill the yeast cell. ...read more.


Modifications If I were to conduct the experiment again, I would conduct all the experiments myself so that I could make sure that the conditions were exactly the same for every solution, and I would know exactly if something had been a bit odd in a certain experiment. I may also test the alcohol concentration after the experiment has finished so that I could see if that had been the limiting factor. I would also continue the experiment for longer so that I could see which solution ended up producing the most gas. With these bits of information, I would be able to work out the effect of alcohol on the solution, and decide if that had been a limiting factor. If I knew how much longer the solutions had continued to produce gas, then I would be able to test my theory that the six and ten percent solutions would continue to produce gas when all the others had finished. If they had done, then I would know that the limiting factor for those solutions had been the fact that the cells were plasmolised, however, if they had stopped producing gas just after the four percent solution had, then I would know that alcohol had been the limiting factor. Hector Guinness 03/05/2007 1 ...read more.

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