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The aim for this experiment is to find which sugar respires best with yeast.

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Aim The aim for this experiment is to find which sugar respires best with yeast. Hypothesis I think glucose will respire best (produce the most Carbon Dioxide) and Arabinose will react least. This is because Glucose 'fits' exactly into the yeast enzyme according to the 'lock and key' theory. Because the Glucose molecule 'fits' in the yeast exactly, it metabolises the best. Sugar molecules, such as Galactose, which is similar to Glucose, may partially react as the substrate may partially 'fit' into the yeast active site, however, it will not fully react as it will not fully fit into the yeast active site. According to the Swedish chemist Savante Arrhenius, the substrate and enzyme form an intermediate substance known as the enzyme substrate complex: S + E --> ES --> P + E Substrate Enzyme Enzyme Substrate Complex Product Enzyme So, if the substrate does not react completely with the enzyme, a 'good' enzyme substrate complex will not be created, so a 'good' product will not be created. Equipment list Conical Flasks Beakers Pipettes Measuring Cylinders Balance Yeast Solution Sugar Solutions: Glucose Galactose Fructose Sorbose Arabinose Diagram Method As we are measuring the amount of Carbon ...read more.


This is not a dangerous experiment so there isn't any need for protective clothing. Results Name of Sugar Initial mass Final Mass Change in mass Average Change % Arabinose 71.13 71.04 0.09 0.23 0.305282718 70.14 70.07 0.07 84.75 84.22 0.53 Glucose 71.08 70.6 0.48 0.483333333 0.68574131 70.17 69.7 0.47 70.2 69.7 0.5 Sorbose 73.74 77.7 -3.96 -4.213333333 -6.107460379 65.42 69.6 -4.18 67.8 72.3 -4.5 Sucrose 86.28 85.15 1.13 1.17 1.327383429 89.2 87.96 1.24 88.95 87.81 1.14 Fructose 69.21 68.55 0.66 0.643333333 0.907722698 70.71 70.08 0.63 72.7 72.06 0.64 Galactose 67.01 71.2 -4.19 -3.946666667 -5.882937494 66.75 70.2 -3.45 67.5 71.7 -4.2 Water 69.65 69.46 0.19 0.19 0.272675086 69.8 69.63 0.17 69.59 69.38 0.21 Analysis The results of this experiment did not have a pattern. How well respiration occurred depended on the structure of the sugars. If the sugar substrate managed to 'fit' the enzyme active site properly, then this will create a 'good' enzyme substrate complex therefore the yeast would then respire well. In the experiment, looking at the graph, Sucrose respired best (largest positive result), and the Sorbose respired worst (largest negative result). ...read more.


If I had to do this experiment again then I would use the same, very accurate, balance for each solution because I think this is where the experiment was at its least accurate. This was a very inaccurate experiment, this is proved by the fact that Glucose was not the sugar that respired most, but it should have been, according to (and further research) The lock and key theory and enzyme substrate complex thing, glucose and yeast should create the 'best' enzyme substrate complex so in turn create the 'best' Product. But Sucrose respired best, an observation that explains this is that Sucrose (sugar cane) is used (in Brazil and other places) with yeast to create ethanol, therefore, it most 'fit' the lock and key mechanism well and metabolise well (because it does create over 4 billion gallons of fuel ethanol per year in Brazil alone). In conclusion this experiment did not go very well, it should have been Glucose that respired best because it is will create the best enzyme substrate complex(as it 'fits' yeast's active site best). Repeating this experiment under more controlled conditions is a good idea because the results of this experiment were very unreliable. ...read more.

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