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Investigation of the breakdown of Hydrogen Peroxide by enzymes in living tissue

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Introduction

Philippa Brook 11SP Set S Investigation of the breakdown of Hydrogen Peroxide by enzymes in living tissue Plan and Research I am going to investigate the rate of reaction between enzymes in potato cells and them breaking down Hydrogen Peroxide, also looking at the effect temperature has on the experiment. Enzymes are present in all cells (usually the mitochondria) of living things. Catalase is the name of the main enzyme found in cells, depending on the tissue and which area of the 'body' it comes from determines how many enzymes are present (and in what concentration). Hydrogen peroxide (H2O2) is very unstable and will decompose breakdown slowly on its own, into water and oxygen, however a catalyst will speed up this reaction. Enzymes are catalysts; a catalyst alters the rate of a reaction, usually speeding it up. Catalyst are also not used up in a reaction, so can theoretically be used over and over again. They use a 'lock and key' method to breakdown or build up. Different enzymes are designed to work with different substrates. Catalase can be used to break down hydrogen peroxide, that is why it will be Catalase in the potato cells that will be breaking down the hydrogen peroxide. The equation for this is: Catalase 2H2O2 H2 O + O2 Catalase Hydrogen Peroxide pure water + oxygen The reason Catalase can be used as a catalyst in this reaction is because Catalase is made up of amino acids (proteins) ...read more.

Middle

If the temperature increases too much eventually the enzymes will break the bond and return form the tertiary structure to the primary structure. The heat causes this. However this will only happen if there is an excess of substrate if there isn't, then the reaction will stop when all the hydrogen peroxide has been used up, in the time allowed. So that at the optimum temperature the reaction will take the same amount of time as when the temperature is just less. I have drawn two diagrams to illustrate this. With an excess without an of substrate. excess of substrate Preliminary experiment I did two experiments for my preliminary, the second was much more successful than the first. I shall use the equipment that I used in my second experiment for my investigation. Below are the two diagrams for each experiment: First experiment Starting mass of potato: 2.9g Starting volume of hydrogen peroxide: 30ml Time (minutes) Amount of gas (ml3) 0.5 0 1 1 1.5 2.5 2 3 2.5 4.5 3 5.5 3.5 7 4 8.5 Second experiment Starting mass of potato: 3g Starting volume of hydrogen peroxide: 25ml Starting temperature: 25� Finishing temperature: 27� Time (minutes) Amount of gas (ml3) 0.5 2.5 1 4 1.5 6 2 7.5 2.5 8.5 3 10 3.5 11.25 4 12 4.5 13.25 5 14.25 The first one went wrong and the results weren't very useful. I did the experiment for four minutes and took readings every thirty seconds and the second was the same except it lasted for five minutes. ...read more.

Conclusion

1.5 5.25 5.25 5.5 2 6.5 6.25 6.5 2.5 7.5 7.5 7.5 3 8.5 8.75 8.5 3.5 9.5 9.5 9.75 4 10.75 11 11 4.5 12 12 12 5 13 13 13.25 For the last repeats of 45� after the first three the results do not match the other two sets of results I have. These are all anomalous. Below is a table with the averages in and in that table I have not used from 2.5 to 5 minutes of 45�. On the graph I have plotted the anomalies though so you can see where the results have gone wrong. Also on the graph I have worked out the gradient of each line so that I could work out the rate of reaction, which is plotted on the next graph �. On the graph I have plotted the anomalies though so you can see where the results have gone wrong. Also on the graph I have worked out the gradient of each line so that I could work out the rate of reaction, which is plotted on the next graph with the temperatures. Average results Temperature Time 25� 30� 35� 40� 45� 50� 0.5 2.583 2.75 2.916 2.916 3.583 3.25 1 3.083 3.416 3.666 4.166 4.583 4.166 1.5 3.833 4.483 4.583 5.166 5.666 5.333 2 4.5 4.666 5.5 6.416 6.875 6.416 2.5 5.333 5.916 6.416 7.166 8 7.5 3 6 6.833 7.583 8.583 9.125 8.583 3.5 6.583 7.583 8.416 9.583 10.25 9.583 4 7.416 8.583 9.416 10.5 11.375 10.916 4.5 8.166 9.333 10.416 11.416 12.5 12 5 8.916 10.166 11.5 12.333 13.625 13.083 ...read more.

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