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Investigate whether pH level affects the rate of reaction for enzymes.

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Introduction In this experiment I am going to investigate whether pH level affects the rate of reaction for enzymes. I am investigating the reaction between catalase and hydrogen peroxide. Catalase is an enzyme found in every living cell. Hydrogen Peroxide is also produced in every living cell as a waste product. Hydrogen Peroxide is also toxic. It breaks down slowly into water and oxygen. Catalase works in the cells to break down hydrogen peroxide into safe, useful products that can be used within the body. Prediction I predict that from my results I will find that catalase has an optimum pH that it works best at. A graph of the results would show that the further away from the optimum pH it is, the lower the rate of reaction will be I think this because the active site of enzymes is very sensitive and changes in pH break ionic bonds that hold the structure of the enzyme together. Also, pH is a measure of the concentration of hydrogen ions. If there are too many or too little of these hydrogen ions, it affects the charges on the amino acids in the active site so that the enzyme cannot fit with the substrate. ...read more.


For my preliminary results I used a pH1 buffer. Amount of Buffer (ml) pH level 10 1.4 20 1.3 30 1.2 40 1.1 45 1.0 50 1.0 My preliminary results show that 50ml of buffer keeps the solution at pH1. The minimum amount of buffer I could use however is 45ml. I will use this amount for my experiment so I don't waste buffer, but the amount is also easy to measure. Results Table pH level Volume of gas produced Test 1 (ml) Volume of gas produced Test 2 (ml) Volume of gas produced Test 3 (ml) Volume of gas produced Average (ml) 1 0 0 0 0 2 0 0 0 0 3 4 1 0 2 4 1 1 1 1 5 2 3 3 3 6 22 18 12 17 7 28 26 20 25 8 25 35 40 33 9 47 48 52 49 Conclusion My graph shows a curve that peaks towards the end. The activity of the enzymes increased to a maximum of pH9. This shows that the catalase seems to work best at pH9. ...read more.


I only repeated it three times, to get a complete idea of the relationship between enzyme activity and pH level I would have to have repeated it a lot more times. Also I could have used a full range of pH levels to get a better idea of the pattern on the graph, and the activity of enzymes in certain pH conditions. I could have improved my experiment by using a constant concentration of catalase. This would have improved my results to make them more reliable as the only factor that would have been changed would have been the pH level. To further this investigation I would have liked to test the effect temperature has on enzyme activity. I would do this by using the same pH buffer to maintain the same pH of the solution, and by changing the temperature of the catalase before I put it into the solution. I would use different temperatures such as 5�c, 20�c, 37�c and 50�c. This way I would have fridge, room, body and a high temperature. This would tell me around which temperature the enzymes work at best. I would predict this would be at around 37�c because it is the same temperature as our bodies maintain, so it would have to work best in our bodies. ...read more.

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