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An investigation into the effect of a substrate concentration on the reaction rate of the enzyme Catalase.

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An investigation into the effect of a substrate concentration on the reaction rate of the enzyme Catalase. Aim The aim on my investigation is to find out how the concentration of hydrogen peroxide (as the substrate) in water, affects the rate of reaction in the Catalase (as the enzyme). Discovering which level of substrate has the maximum effect on the enzyme activity. Prediction I predict that the higher the concentration of Hydrogen Peroxide the more Oxygen will be produced and the oxygen will be produced in a faster time. I think this because as the concentration increases, so do the number of Hydrogen Peroxide molecules in the same volume meaning the chances of the H2O2 coming into contact with the active site of the Catalase enzyme increases - making the chances that oxygen will be produced higher. Hypotheses "The higher the concentration of the Hydrogen Peroxide the more oxygen will be produced - oxygen will also be produced at a higher rate." Key Science The key science behind this investigation is how enzymes work. Enzymes work as bimolecular catalysts that speed up chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules. Almost all processes in a biological cell need enzymes in order to occur at significant rates. Since enzymes are extremely selective for their substrates and speed up only a few reactions from many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. Enzymes are generally globular proteins and range from just 62 amino acid residues in size. Enzymes are specific because both the enzymes and the substrate possess specific complementary geometric shapes that fit exactly into one another. This is often referred to as "the lock and key" model. Most Enzymes also work best at around 37 degrees Celsius 2 H2O2 � 2 H2O + O2 Catalase Catalase is a common enzyme found in ...read more.


ml 18 ml 18 ml 10% 5 ml 12 ml 14 ml 17 ml 19 ml 19 ml 19 ml 10% 4 ml 12 ml 13 ml 16 ml 18 ml 18 ml 18 ml 15% 17 ml 25 ml 28 ml 34 ml 37 ml 37 ml 37 ml 15% 16 ml 22 ml 28 ml 33 ml 36 ml 36 ml 36 ml 15% 16 ml 23 ml 28 ml 35 ml 38 ml 38 ml 38 ml 20% 18 ml 29 ml 40 ml 43 ml 45 ml 46 ml 46 ml 20% 17 ml 27 ml 37 ml 40 ml 42 ml 44 ml 44 ml 20% 18 ml 28 ml 39 ml 42 ml 43 ml 45 ml 45 ml Changes to be made to method I am going to make a few changes to my method; Firstly I am going to dissolve the yeast instead of adding it straight into the water this is because the surface area yeast granules will affect the over all result as if the surface area is greater the more area there is for the hydrogen peroxide to come into contact with the enzyme - making a reaction more likely. As the granules in my preliminary where all of a different size it made the test unfair. It would be impractical to search for yeast granules that were all exactly the same size so instead I am going to dissolve them instead. Secondly I don't think there is any need to change the; amount of yeast, hydrogen peroxide or water as the foam never reached the top and I was always able to see the difference in hydrogen peroxide levels every 10 seconds. There was a slight error in each experiment as when the bung was pushed in it would displace some air into the measuring cylinder that was measuring the amount of oxygen produced. ...read more.


This would help me get a more precise set of results and graph and I would be able to see each stage of the reaction more clearly, which would have helped my analysis a bit more. To do this I think I would have had to do it electronically. I would also need to find a new way of measuring the volume of oxygen in the measuring cylinder. I could use a thinner measuring cylinder with more accurate measurements on the side and I could also add ink to the water so it would show up more clearly against the measurements. Conclusion of Results The results I got fit the pattern I predicted. There were no outliers in my data table and the largest applicable error bound was 27%, even though this number seems large the results evened themselves out to a 12% error bound within the next 10 second interval. This shows that the reaction "caught up" with other reactions The reason for all these anomalies is that maybe my method slipped up for reasons I have said previously - which meant some results were very close together and some were very far apart. The only difficulty I encountered when doing my experiments, was starting the stop watch, because I needed to put the stopper into the test tube at the same time, but I got over this problem by asking someone close by me to start it for me. I could have taken my investigation further, by heating the hydrogen peroxide to 37�C, which is the optimum temperature for enzymes. This would have meant that the enzyme would be at its peak activity rate, so more oxygen would have been produced in the same time, because there would have been more successful collisions. I could also have measured the room and water temperature. I do not think that it changed to dramatically over the course of my investigation so I thought it would not be the best use of my time. ...read more.

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