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An investigation into the breakdown of Hydrogen Peroxide by Catalase.

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An investigation into the breakdown of Hydrogen Peroxide by Catalase Background Theory An enzyme is a protein. It is a globular protein - its molecules are round in shape and they usually have an area shaped like a pocket. This 'pocket' is called the active site. This is the area where a substrate can join the enzyme and be divided into two or more products. It can be compared to a 'lock and key' system, the lock being the substrate, and the key the enzyme. This is demonstrated in the diagram below: ENZYME ENZYME and SUBSTRATE ENZYME We could think of this process as similar to a person catching a ball. As the ball enters the person's hands they close around it. In the case of the enzyme, the 'ball' is the substrate and the 'hands' the enzyme. The enzyme 'catches' the substrate and then it puts pressure on the bonds within it. This pressure weakens the bonds between the two or more products and they therefore break away from each other. An enzyme is a biological catalyst. It will speed up a reaction or just facilitate the reaction on its own. The more enzyme that is present in the reaction the faster the reaction will take place, and the more products will be formed. An enzyme is never used up in a reaction, but can denature due to excessive heat, exposure to toxins or change in pH. ...read more.


When carrying out any experiment it is necessary to recognize the variables, and whether they are fixed or not, within the procedure. To decide what was going to be kept constant we carried out preliminaries. What was found is shown here: Length of Potato (cm) Time (secs) Amount of H2O2 Used (cm�) Oxygen Produced (cm�) 1 60 5 0.3 1 120 5 0.7 3 120 10 2.1 3 180 20 2.8 5 180 30 7.2 9 120 30 8.7 From these results it was decided that the best combination of variables was as follows: * Time: Fixed: 2 minutes * Volume of H2O2 needed: Fixed: 30cm� * Length of potato: Variable: 1 - 5cm * Concentration of the H2O2: 2M The decision was taken that the time would be fixed, otherwise the results would not be comparable to each other. To give a good spread of data it was decided to use 30cm� of H2O2, for the more reactant available the more likely that the reaction will last out the two minutes. If the reaction stopped before the two minutes was up then once again the results would not be comparable. In any experiment there must be at least one variable, in this case it is the length of the potato cylinder. The lengths will be 1 - 5cm, with the procedure for each length being repeated three times. ...read more.


Care was taken that each time the stop clock was started after the bung was inserted. Overall this was quite suitable for what was required. It would have been ideal if there were two people carrying out the experiment together to ensure that all of the procedure was done at the correct time. Ideally four or five attempts should have been carried out at each length rather than three. This would give far more accurate results and avoid the type of anomalies such as that of the 3cm measurements. In summary, if the experiment were to be carried out again or simply extended then the following changes could have been made: 1. Rather than just 3 repeats four of five should be carried out. 2. Due to the limited lengths of potato the graph provided a small snapshot of the relationship. It would therefore be useful to increase the number of lengths to extend from 1 - 10cm. 3. A second person should be present to help carry out the experiment. In accounting for the anomaly in the set of results evidenced by the 3cm length, perhaps this was due to human error. On the whole this did not really upset the conclusion drawn from the results, but introduced the possibility of an exponential relationship between the amount of oxygen produced and the amount of catalase present. This was because in the next result there was a dramatic increase in the production of oxygen. This conclusion cannot be made without the provision, and examination of a greater number of results. Luke la Hausse 4 alpha ...read more.

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