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My hypothesis is that the higher the concentration of hydrogen peroxide the more catalase would be catalysed

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Introduction

Biology coursework: Catalase and hydrogen peroxide Introduction My experiment is about the effects of the concentration of hydrogen peroxide used, on the reaction rate (how long it takes for a reaction to happen). My hypothesis is that the higher the concentration of hydrogen peroxide the more catalase would be catalysed (a catalyst is a chemical that speeds up a reaction without being used up itself) in a minute so more oxygen gas produced. This means that the rate of reaction is quicker. This is because in a low concentration of hydrogen peroxide there are many unoccupied active sites so the rate of reaction is low and a smaller amount of products will be formed in a set amount of time. When the concentration of hydrogen peroxide is increased more enzyme-substrate complexes can be formed for the same amount of catalase, increasing the rate of reaction and the products also increase as a result. Increasing the concentration further will have no effect to the rate of reaction because all the active sites will have been occupied and no more enzyme substrate complexes can be formed. H2O2 + catalase H2O + O2 Hydrogen peroxide Hydrogen peroxide (H2O2) is a poison produced by all cells, and is a clear liquid commonly used in bleach. It is used as an antiseptic, disinfectant, oxidiser and as a propellant in rocketry. Hydrogen peroxide is considered as a highly reactive oxygen species. The pH of hydrogen peroxide is 6.2 but can become as low as 4.5 when diluted (a solution that has more water) 60 percent. Catalase Catalase is an enzyme (biological catalysts that break down or put together substrates) that breaks down Hydrogen peroxide into water and oxygen. It is found in nearly all living cells and is used for hydrolysis (breakdown) of hydrogen peroxide. Catalase like all enzymes are made of proteins(DNA controls how a cell functions by controlling what proteins are produced) ...read more.

Middle

* Thermometer- used to measure the temperature of the solution before and after the reaction to get an average overall temperature. * 25ml measuring cylinder (2)-was used in place of a 50ml measuring cylinder to measure the volume of distilled water and hydrogen peroxide added because it will be more precise. * Stopwatch- used to run the experiment for exactly a minute allowing time for human reflexes. * Stirring rod- was used to stir the solution to make sure that the hydrogen peroxide was evenly spread. * Distilled water- was used to make sure that there were no contaminants from the water which would affect the rate of reaction. * Hydrogen peroxide * Water * 50ml measuring cylinder * Yeast * Weighing boat * Large test tubes (12) * Boss, stand and clamp * Bowl of water * Bung with delivery tube * Pipette (2) * Test tube rack * Funnel-was used to get the distilled water into the burette. Revised method > I measured out 1ml of hydrogen peroxide and 3ml of distilled water (25% concentration), then 2ml of hydrogen peroxide and 2ml of water (50% concentration) and so on for 75% concentration and 100% concentration. I did this by measuring out the volume of water and hydrogen peroxide needed in a 25ml measuring cylinder using a pipette. The hydrogen peroxide and water was put into a test tube and stirred for five seconds with a stirring rod and placed in the test tube rack. Then I put a weighing boat onto the weighing scale (which reads correct to 3 decimal places) and pressed he 'tare' button to make the weight was 0 grams in order to measure the weight of the yeast added. Then I added small amounts of yeast till the weight was 0.2 grams. The scale that reads correct to 3 decimal places is more accurate than the scale that reads to 1 decimal place. ...read more.

Conclusion

Having said that it is not feasible to have an experiment with none of the variables affecting the results either. Reliability of evidence Valid results were not that very hard to collect and there was only one anomaly in both my preliminary and revised experiment. There was only one anomaly in all of my results and I realised it during experimentation so decided to retake it. In my table I put the anomaly, identified it but did not take it to account when finding the mean but used the retake result and made it clear that it was the retake result. The reason for an anomalous result I cannot be sure of but there are many explanations, such as cross contamination so something like a little bit of hydrogen peroxide was left in the test tube or got into the test tube. Some human error could also be an explanation because I might have misjudged the amount of hydrogen peroxide added and added too much or too little. The scale might have been faulty when measuring out the yeast so there might have been more enzymes with active sites available than there should be so more hydrogen peroxide is catalysed and more oxygen (product) is produced. On the other hand it could have been because there was a little less yeast and so there were less enzymes with active sites than there should be, so there is less hydrogen peroxide being catalysed so less oxygen is produced. The trials had these results: 15, 19 and 22 with the retake 18. 15 was the anomaly so there must have been a bit less catalase in that experiment or I might have thought there was the right amount of hydrogen peroxide when there was too little. Reliable results depend on the method and I think that my method was a slightly lengthy but reliable one. Therefore my results would be reliable as well and I stuck to my method and did not change it in between. ?? ?? ?? ?? Rawzim Nifuhan 10V2 10C ...read more.

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