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How pH affects the rate of enzyme reaction

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Introduction In this piece of work I am going to investigate how pH affects the rate of enzyme reaction. There are some chemical reactions which take place in the cells of both plants and animals. These produce a substance called hydrogen peroxide, and could poison the plant if it were left to accumulate but many plants contain an enzyme called peroxidase , which acts as a catalyst for decomposing hydrogen peroxide into water and oxygen. A catalyst is something which changes the rate of a reaction without actually being changed itself The reaction which will take place is : Hydrogen Peroxide + peroxidase � Water + oxygen I will gain peroxidase from ground celery. I know that enzymes work better as the temperature increases until it reaches its optimal, after which the rate decreases again. So I will keep the temperature constant at room temperature, although this may gave fluctuations. I must keep all other variables the same to make it a fair test, for example if I didn't use the same amount of acid as I used peroxidase, I couldn't fairly say that the acid affected the result, because it may have been a lack or increase in the enzyme. ...read more.


we repeated for strong acid, weak acid , neutral, strong alkali and weak alkali. We tried to make it as accurate as we could, by using exactly 5ml of each component, not deliberately altering the temperature, only room temperature fluctuations maybe. I was very careful with all of these and I made sure I filled the gas measuring cylinder completely and tried to keep it like that. Analysis The following table shows my results for our investigation. We only had time to do 2 sets for all pHs as it was a difficult experiment to do quickly, and we had to wash all equipment after each experiment. Experiment 1 Weak acid Strong acid Weak alkali Strong alkali neutral 15 5 8 11 10 9 30 7 9 17 17 13 45 8 13 31 23 17 60 8 14 42 28 23 Experiment 2 Weak acid Strong acid Weak alkali Strong alkali neutral 15 5 5 11 9 7 30 7 8 18 14 8 45 10 9 32 14 12 60 12 9 32 18 16 The following pages show graphs for averages and lines of best fit. ...read more.


I also done strong alkali on a different day to weak alkali, this could of affected many things. The room temperature could of varied quite drastically , which would have an affect on my results. And I used different celery on both days. The celery may have contained more peroxidase than another. There are many other things which could have changed, my measurements could have been inaccurate. If I was to do this experiment again I would collect at least three sets of results before working out an average. This would of helped with them. I would also of tried to keep the temperature constant by doing it all in one day , or maybe even using a water bath. I would of used the same celery for all , and kept my measurements as accurate as I could. I could also do it at more intervals to get a better line of best fit and more accurate graphs in general. Overall I would say my results were quite accurate, but more testing and revising the alkali tests would make this a much more reliable experiment. By Lawrence Bell ...read more.

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