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Rate of reaction using enzymes

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Biology Coursework: Rate of reaction using enzymes In this bit of coursework I will be investigating the rate of reaction in which enzymes are the catalyst breaking down a substrate. The substrate I am going to use is Hydrogen Peroxide (H2O2, water with another Oxygen), this molecule usually breaks down on its own accord, but also the rate of decomposition can be increased with the use of a catalyst; in this case the catalyst is a biological one called an enzyme. Hydrogen Peroxide slowly breaks down on its own accord into water (H2O) and oxygen (O2): 2 H2O2 --> 2H2O + O2 Hydrogen Peroxide --> Water + Oxygen In my experiment, I want to investigate the rate of reaction with an enzyme, and the enzyme I will add to the Hydrogen Peroxide will be Catalase. The enzyme will accelerate the rate of reaction without being used up, for that is a property of a catalyst is, it speeds up a reaction without being used up, and an enzyme is a biological catalyst. Method Before doing my 'actual' experiment from which I would take my data and ultimately come up with a conclusion I did a preliminary experiment, which was for a number of reasons. Firstly, I had no previous experience of doing this reaction and so needed an idea of how it went: how quickly, how much oxygen was produced and what measurements to use. Also there were two different experiments in which I could have got my data from, one of the experiments was relatively simple and the other more complex but also more accurate. The first experiment I had a choice to do was one in which I had a rack of six test tubes; the procedure I had to follow was simple, I had to put 5cm3 of different concentrations of Hydrogen Peroxide ranging from 0%-100% in each of the test tubes slowly, this was so I did not lose oxygen by giving the substrate energy to break down before the experiment had started. ...read more.


* The same angle of the gas syringe has to be used. If the angle is difference then the force of gravity on the syringe will be different, and therefore the oxygen will be able to push it easier/harder depending on which the change in angle has occurred. * pH. The pH can affect how the enzymes reacts, either by slowing them down or speeding them up; most enzymes only work well in a certain pH and can only tolerate a slight change of pH to either side (+1 or -1). I can do little to control this factor. * Atmospheric pressure can affect the volume the oxygen takes depending whether or not it is high or low pressure. In order to get round this I will try to do all the experiments on the same day, if I cant then there is nothing I can do about this factor. Obtaining In my investigation I used equipment that is suitable for it and that would help me conduct it, for example I used a gas syringe to collect the oxygen given off instead of using the first technique, which involved detergent and the gas being collected in it, this is unreliable. I used the gas syringe because it is relevant for my investigation; there are two ways in which I could measure the rate of reaction these are: 1. measuring the rate at which the reactants are being used, it is difficult to measure this in this reaction. 2. Measuring the rate at which the products are given off. I chose to measure the rate at which the products are given off because it is easy in this experiment, the product is a gas and can easily be collected in a gas syringe. The easiest and the most accurate way in which to measure the gas being given off was to use a gas syringe and so I did. ...read more.


The results were the same from the repeated experiments, other people in the class were having the same results, and so they are not anomalies. On my 'volume of gas given off after time' graph, you can see I have circled two crosses in different colours; the two colours represent different concentrations used. But the circles round them mean that they did not fit on the line of best fit that I drew through the majority of the points, the line of best fits indicates the expected rate of reaction between the two points on the graph. Therefore, these are the two anomalies in one of my complete experiments. One of the ways to make sure that anomalies do not affect my investigation is to repeat the results; I did this and so used all my data in my investigation and so the anomalous results did not affect the conclusion. Conclusion As the concentration doubles the: * Volume of gas given off doubles because there are twice as many particles of H2O2 that decompose into oxygen, and if left until the reaction is complete then there will be twice as much oxygen. * Rate of reaction will double because there will twice as many particles and therefore the chance of a collision between the reactants with enough energy will be double, and therefore the rate of reaction will be twice as quick. This is true until the maximum rate of reaction is reached, an enzyme only works up to a maximum speed. All the data I have collected backs this conclusion up until 50% were things don't seem to fall into place. But in the experiment I did on the first day you can see that it supports my conclusion al the up until 100% concentration. This is true up until the maximum rate of reaction of an enzyme is reached; an enzyme has a maximum rate of reaction and can work proportionally quicker as a factor proportionally increases until it reaches a maximum rate of reaction. ...read more.

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