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To find out how the rate of reaction of yeast can be increased

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Ashley Meighen G.C.S.E. Science Coursework Science investigation Aim The aim of my investigation is to find out how the reaction of yeast can be increased. I'm going to do that by measuring the rate of reaction. This is the reaction I am going to speed up: Yeast + glucose Energy + CO2 (Zymase) + Alcohol From this equation I think that the best way to do this is to measure how fast the CO2 is given off and to count the number of bubbles given off. Planning I know that yeast respires aerobically and I also know that yeast uses an enzyme called zymase, which, is a biological catalyst. Again using the same equation as before it will help me with my investigation because I will add glucose to the yeast, and measure how fast the CO2 is given off. This will indicate the rate of the reaction. Research Substances called catalysts can speed up many chemical reactions. A catalyst alters the rate of a chemical reaction without being changed itself. In my investigation I'm looking at a biological catalyst called zymase. A chemical reaction always involves one substance being changed into another. The substance that is present at the beginning of the reaction is called the substrate. The substrate that is made by the reaction is called the product. The products in my investigation are CO, energy and alcohol. ...read more.


Denaturing is when the temperature reaches its highest point for the enzyme to work and then the reaction slows down. I predict that my results formed into a graph will look like this: Fair Test I will make it a fair test by using the same type of yeast-as some may have different surface areas than others, use the same type of glucose because the particles may vary, use the same ph because it would affect the enzyme, use the same burette as it has the same calibrations, use the same apparatus throughout as it may cause anonymous results if you don't and most important make sure the readings are taken at the right time and temperature. Results Volume of CO2 : Temperature 1 min 2 min 3 min 4 min 5 min Average 20'c 0.4 0.1 0.1 0.5 0.3 0.28 30'c 3.5 2.6 2.5 2.5 1.0 2.24 40'c 4.0 2.5 3.5 1.5 3.5 3 50'c 4.0 2.0 1.5 1.5 1.5 5.7 60'c 2.0 1.0 0.5 0.2 0.1 0.76 70'c 2.0 0.2 0 0 0 0.44 80'c 0 0 0 0 0 0 Number of bubbles: Temperature 1 min 2 min 3 min 4 min 5 min Average 20'c 3 2 4 6 6 4.2 30'c 36 26 26 27 28 28.6 40'c 73 52 47 41 35 49.6 50'c 80 51 40 31 27 45.8 60'c 49 21 13 8 6 19.4 70'c 40 6 0 0 0 9.2 80'c 0 0 0 0 0 0 Apparatus Method We are going to measure the rates of reaction in yeast. ...read more.


So to see if it is, I heated it up again by 10oc and even less C02 was given off. After taking the second reading there was no C02 given off this means the enzyme is denatured. So that meant that 50oc was my optimum temperature. So to my prediction, I said for every 10oc rise in temperature it will double the reaction. This did not happen so I was wrong. On my graph I have drawn there were anomalous results, I have identified these by circling them. Evaluation The apparatus I used had a small scale so they would be accurate, and I tried to make it a fair test, by taking 5 reading and using the average to make a graph, and I still got anomalous results. The experiment was very difficult to perform, because you had to watch for bubbles and write down your results as well. That's why I used a table to record my results so it was quick and easy to record. It was also hard to count the volume because the burette was upside down. It would have been more accurate if I used a gas syringe. Also a plastic tube was not airtight so I put Vaseline around the top to stop gas escaping. The tube could easily get blocked if the burette went down to the bottom of the water, and trapped the tube squeezing it together, so if I did the experiment again I would uses a gas syringe and maybe different types of yeast and sugar as well. ...read more.

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