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Experiment to Show the Respiration Rate in Yeast

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G.C.S.E Biology Experiment to Show the Respiration Rate in Yeast Introduction This experiment has been set up to show the respiration rate in yeast over a range of different temperatures. I have done this to find at what temperature yeast respires the highest. I will be using a range of temperatures from 10?C to 70?C with intervals of 10?C. After using the temperatures 20?C and 40?C in my pilot experiment, I will repeat the experiment with a range of temperatures being: 10?C, 20?C, 30?C, 40?C, 50?C, 60?C and 70?C. I will be using this wider range to find the optimum heat capacity. Hypothesis I predict that the yeast's respiratory rate of reaction should increase in speed as the temperature increases. However this may at some point peak and therefore cease to increase in speed as I predict at some point the enzymes causing the yeast to respire will become denatured. The point of this investigation is to find the optimum heat capacity of the enzymes in the yeast. At this point there will be the optimum rate of reaction. I then predict that the rate of reaction will drop after this optimum rate as the enzymes will become denatured and will no longer fit their substrate. I believe this because yeast is a unicellular fungus, and can respire both aerobically and anaerobically. ...read more.


60 24 24 24 30 31 35 39 40 43 50 52 57 60 65 71 64 67 75 68 70 77 71.7 70 24 24 24 26 25 25 28 28 30 36 41 44 41 48 50 44 53 54 46 55 56 52.3 Conclusion After repeating my pilot experiment with a wider range of temperatures I have found that at 50?C the enzymes are nearest their optimum heat capacity and caused the dough to rise the most. It rose due to the enzymes anaerobically respiring. At 50?C the yeast rose by 99.0 cm�. This was because the enzymes in the yeast had more kinetic energy at this temperature. In my hypothesis I predicted, with the help of my pilot results, that the higher the temperature, the more carbon dioxide will be produced until it reaches a certain temperature. Using my scientific knowledge, I know that most enzymes are denatured at 100?C. I predicted that maximum carbon dioxide would be produced at the highest temperature I used which was 70?C. My results prove this was not so as by viewing the graph I can tell that at 60?C the carbon dioxide produced was 28 centimetres cubed. This is due to the fact that the enzymes had already begun to denature. I could do more temperatures between the ranges of 40-60? ...read more.


The amount of yeast will also have an effect on the results; as if we are to use different amounts in each experiment it will form an unfair test. Another factor that could affect our investigation is the percentage of glucose in the yeast. I overcame this by ensuring that an equal amount of glucose in each mixture. I must also make sure to leave all experiments undisturbed during the course of respiring; this means they cannot be stirred. Due to all these factors the results will not be 100% reliable. There will always have to be room for error due to human error. I feel that the results are enough to support my conclusion as all what I had predicted to come true has done. Although I did have a couple of anomalous results with the 50?C it did not affect my overall results. The results I obtained were not that reliable, as the equipment I was working with was not very advanced. We could not keep the cylinders at the precise temperatures all the time, as we did not have the equipment available to do so. Also the readings could be very slightly out as the mixture forms a meniscus on the cylinders, but I took this into consideration as I took the readings so I believe the readings in themselves are accurate. Overall I think that my experiment proved my hypothesis correct and I am pleased with my results. ...read more.

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