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The Decomposition of Hydro Peroxide.

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Introduction

___________________________________________________________Christina Hardinge Science GCSE Coursework: The Decomposition of Hydro Peroxide PLAN: Aim: Investigate the effect of different pH's on the enzyme catalase. Prediction: After carrying out research on the internet (www.CPG.com) I believe that the enzyme catalase will work best at pH7. Hypothesis: The chemical equation of catalase' reaction on hydro peroxide is: The pH affects the activity of enzymes, the enzyme activity reaches a peak at a certain pH and if the pH is above or below this optimum level the enzyme activity falls. In the case of catalase the optimum pH level is 7. We know enzymes generally work best at neutral as very few living organisms can survive at extreme acids or alkalis. This diagram shows what happens to the catalase at pH7. This diagram shows the effect of extreme acids and alkalis. As you can see the active site changes so the substance cannot fit anymore so it is not broken down. This process is denaturing. This is shown in the reaction because when extreme pH buffers are used, little froth (oxygen and water) is produced. Safety: ~ Wear goggles and hair tied back. ~ Use plastic gloves. ~ Use a pipette for the buffer. ...read more.

Middle

However rather than rising to pH 7 and then falling at the same rate again, the results fall at pH 9 and then slowly rise at pH 14. I didn't expect this because my hypothesis shows that the catalase is mainly denaturized at the extreme acids and alkalis, pH 1 and pH 14. CONCLUSION: My results support my prediction and show catalase is most reactive at pH 7 as it has shown more froth than others, and thus is the optimum pH for catalase. FLAWS IN THE METHOD: ~On a few occasions the froth overflowed from my measuring cylinder, and to have prevented this from happening I should have used a taller measuring cylinder or decreased the volume of hydro peroxide. ~It was very difficult to achieve the exact same shape and weight of the liver each time which means there would have been a different amount of catalase each time. Also it means there was not always the same amount of surface area exposed, which could affect the number of collisions. This is because a catalyst works by giving the reacting particles a surface to stick to where they can bump into each other. Therefore, if there is a larger surface area for the particles to stick to there will be more collisions ~When I first began the experiment I used fresh liver, however I used the same liver when I resumed with the experiment four days later. ...read more.

Conclusion

EVALUATION: Overall, I am pleased with my method as I was able to achieve a height of froth measurable, that it was a fair test and that my results are as I predicted. My evidence is reliable as I tested each experiment three times to find the average which meant my results were more dependable. The only anomaly I experienced was that for the end results the activity increased at pH 14 rather than decrease (I commented on this in my results). Reasons for this could have been my equipment was dirty, the liver could have been fresher for this experiment, the hydro peroxide could have been stronger or fresher, and also it was extremely hard to maintain the same shape and weight of the liver used. To improve these faults I could begin and finish the experiment all on the same day, as room temperature and the freshness of the liver could change within days, I could clean my equipment more thoroughly or use new equipment for each test, and I could have used other pH values for a more accurate result. For example I could have tested pH 10, 11 and 12 to find out exactly when the results begin to fall and rise again. ...read more.

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