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An experiment to investigate how a substrate affects the rate of reaction of the enzyme catalase.

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An experiment to investigate how a substrate affects the rate of reaction of the enzyme catalase In this experiment I will be investigating the following reaction: This experiment uses hydrogen peroxide as the substrate and potato chips as the enzyme. Potato contains the enzyme catalase and I will be investigating how the rate of reaction is affected when hydrogen peroxide is put together with the potato (catalase). To begin this experiment I will find out the factors that affect the rate of reaction of the enzyme Catalase when put in with hydrogen peroxide. I will then choose one of these. This will be the variable that I will change during the experiment and therefore vary the rate of reaction. The factors that would affect the rate of reaction are as follows: * Temperature of the substrate, hydrogen peroxide: The temperature at which the experiment is conducted will affect the speed at which the reaction happens. This happens because the enzyme and substrate particles move around faster when the temperature is increased, as a result of the particles moving faster they collide with each other more frequently and so the reaction becomes faster. This is known as the collision theory. The major problem with increasing the temperature of the substrate is that the hydrogen peroxide becomes more of a hazard. Hydrogen peroxide reacts with substances and gives of pure oxygen, when it is heated up it reacts faster because of the collision theory and so gives of more pure oxygen. Pure oxygen is dangerous for two reasons; 1) if the oxygen was to come into contact with a naked flame it would combust, which would be dangerous to all around it. 2) Pure oxygen is poisonous to people if they have too much, the air that we breathe has only a small percentage of oxygen in it and so if we were to breathe in a large quantity of it, it could harm us. ...read more.


After I did this once more I saw that the results I was getting were inconsistent, this was because the foam was always higher on one side than it was on the other. I decided to find another way to measure the rate of reaction, I looked in a science book and saw that the experiment could be carried out using the oxygen given off to measure the rate of reaction. I decided that this would be more reliable and so I set up some new apparatus. I used the same water bath and test tube system but this time I used a delivery tube and collecting tube to collect the oxygen that was being given off. I also decided that the chips of potato were too big and didn't have a large enough surface area to allow the hydrogen peroxide particles to react with, so I cut them into quarters so I ended up with 32 potato chips. This allowed the substrate to react with more enzyme particles and cause a faster reaction. The oxygen collecting method worked much better than the measuring foam method, I did it twice, one with 100% concentration and the other with 60% concentration to make sure it worked I got consistent results to what I expected to happen, this helped me to make my prediction of what I believe is going to happen. Preliminary results Concentration Oxygen collected (cm�) (1) Oxygen collected (cm�) (2) 60% 14.1 14.8 100% 17.5 18 As a result I decided to use this method in my real experiment. Below is a diagram of the oxygen collecting apparatus that I will use in my actual experiment: From doing the preliminary work I believe that I can make a realistic prediction as to what will happen in the real experiment. I think that as the concentration of the substrate is increased the more oxygen will be produced in the time. ...read more.


I think that the results that I got from the experiment are enough to justify a valid conclusion, this is because they reflect the lock and key theory, and they also reflect the research I did into the experiment from an AS level biology book. I think I could have done some things to make the evidence I got a bit more reliable. I could have extended the enquiry to get more results from the concentration experiment, this would have given me more reliable results and helped me come up with a more accurate conclusion. I could also have tried a different experiment such as the size of the enzyme and how it affects the rate of reaction. Although I said that this would have been a difficult variable to control I feel that if I had been careful to get the right sizes of enzyme each time it would have given me results that I could use to come a more extensive conclusion about what affects the rate of reaction. In this experiment I could have made the results more reliable by getting the enzyme into the substrate by using a syringe to inject it into the test tube. This would have deleted the problem of losing oxygen whilst I put the bung onto the test tube. This would have meant I would have to cut the potato to a very small size and would have made controlling that variable quite difficult because I couldn't be sure to cut it to the same size each time. Overall I think that this experiment went very well, I got the results I expected and the experiment went without major incident other than the one small anomalous result, this was quite good although it would have been better if I'd got none. The anomalous result didn't affect the outcome very much and so it didn't seem too significant. The evidence that I got allowed me to come to a good conclusion about how the concentration of a substrate affects an enzyme. ...read more.

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