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Investigating the effect of pH of Hydrogen Peroxide upon the activity of Catalase

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Experiment: Investigation as to whether the pH level of Hydrogen Peroxide will influence the activity of the enzyme Catalase. Variables involved: Different pH levels will affect the Catalase enzyme by determining whether the enzyme activity will increase, decrease or if it will denature altogether, so the pH level of the Hydrogen Peroxide, which Catalase breaks down into oxygen and water, will be our independent variable. The temperature of the Hydrogen Peroxide will affect the rate of reaction with the Catalase, thus this will be a controlled variable and will need to be kept constant. The substrate concentration can also affect enzyme activity in regards to its rate of reaction, so this will also need to be kept constant. The amount or volume of the chicken liver needed to get the Catalase enzyme can also affect the rate of reaction; therefore this will also be needed to be kept constant. I will also be using buffer solutions to change the pH of the Hydrogen Peroxide, thus the amount or volume used will also be kept constant. All these variables can affect the rate at which oxygen is broken down from Hydrogen Peroxide by the enzyme Catalase, so the measurement of how much oxygen is diffused will be our dependent variable. How to deal with the variables: The pH level of the Hydrogen Peroxide is the independent variable and so must be adjusted. This can be achieved by the use of buffer solutions that are able to change the pH levels. Thus in this experiment, they will be used to change the pH level to the pH's 1, 4, 10 and 14. A pH probe will be used to show this occurring. The temperature of the Hydrogen Peroxide will be kept constant as it will be placed in a water bath that has its temperature level set to 30�?. This will accurately and effectively ensure that the Hydrogen Peroxide is all at the same temperature. ...read more.


on that day, so therefore I measured the temperature with a thermometer and had the water bath in a beaker. This is much less accurate than an electronic water bath, so this is acknowledged as an uncertainty. Another uncertainty could be that my reading on the gas syringe for the result of the amount of oxygen produced might not be accurate, and so therefore could also affect my results. Furthermore, the time limit of recording the reaction between the Catalase and the Hydrogen Peroxide solutions could have affected the outcome in that I only recorded for 5 minutes, but maybe the results would have been different if I had extended the time limit and let the experiment go for longer, so this is also considered as an uncertainty. Analysis: Mean Oxygen given off by Hydrogen Peroxide (pH 1) 0.3 Oxygen given off by Hydrogen Peroxide (pH 4) 2.3 Oxygen given off by Hydrogen Peroxide (pH 7) 27 Oxygen given off by Hydrogen Peroxide (pH 10) 14 Oxygen given off by Hydrogen Peroxide (pH 14) 0 The above table displays the mean of the different Hydrogen Peroxide solutions with different pH levels. The following indicates the standard deviation of both year groups, i.e. taking individual values and comparing how far away they are from their mean value: Standard Deviation SD (Hydrogen Peroxide, pH 1) 0.47 SD (Hydrogen Peroxide, pH 4) 1.7 SD (Hydrogen Peroxide, pH 7.5) 1.6 SD (Hydrogen Peroxide, pH 10) 1.2 SD (Hydrogen Peroxide, pH 14) 0 The standard deviation values above are quite low. Low standard deviation indicates that the data shows less variation from the mean value, while high standard deviation indicates the data being a wider variation from the mean. By definition, this would mean that the data is quite reliable. Significant difference in the oxygen levels given off by Hydrogen Peroxide pH 1 and pH 4: t Stat 1.6 t Critical two-tail 2.8 T-Test: Two-Sample Assuming Equal Variances In my data processing of the oxygen levels given off by ...read more.


Another weakness could be that my decision to only record 5 minutes of the rate of reaction once the Catalase has been added to the Hydrogen Peroxide solutions could have hindered any further possible chances of oxygen given off being recorded. Also, the Catalase enzyme that was used had been taken from chicken liver. For the first two sets of my experiments, the Catalase was taken from the same chicken liver, however, for my third set of experiment the chicken liver was changed to a fresh new chicken and this could have affected my results and could be taken into consideration as an error. There were also limitations to the experiment. I did my experiment with several other people who were doing theirs, and between us there were only 4 measuring cylinders to be shared and so this slowed down my experimentation process for having to wait in turn to use the equipment. We also had to share a limited amount of the chicken liver and the Hydrogen Peroxide solutions. Also, there were only two electronic water baths that catered to many people that wanted many different temperatures for the water bath. Thus, this limited my options in using the electronic water bath and made me use a Bunsen burner and beaker for a water bath in my third set of experiment. To improve this experiment, I could have also done one where I looked at the other factors that affected the enzyme activity of Catalase, like temperature or substrate concentration for example if I had more time. Then I could have compared the results between the factors, and see the similarities and differences. The levels of pH that I used could have also been improved, in that I could do another experiment of a similar kind but focus on closer pH levels to the optimum pH level, so that I get a more accurate account of the enzyme activity . ?? ?? ?? ?? 1 ...read more.

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