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I am going to investigate how a variable affects the rate of reaction in an enzyme.

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Introduction

I am going to investigate how a variable affects the rate of reaction in an enzyme. What is an enzyme? An Enzyme is a catalyst that speeds up the rate of a chemical reaction in an organism. Enzymes are made up of proteins and chains of amino acids. Enzymes can either break down large molecules into smaller molecules or join together smaller molecules to form a longer molecule. Enzymes (catalase in particular) in the human body have an optimum working temperature of 37�C (This is the core temperature of a human body). The enzyme starts to denature over 40�C the enzymes active site starts to denature. The 3�C difference gives the body some leeway when the core temperature goes up due to an illness. The optimum pH of enzymes in the body is around pH 7. Any lower or higher the enzyme starts to denature. And the active site loses its shape. The substrate can no longer 'fit in' and hence the the reaction slows down and eventually stops when all the enzymes active sites are denatured. Variables that affect rate of reaction: 1. Enzyme concentration - to change the enzyme concentration one needs to mix a pH buffer (pH 7) and keep a constant temperature at different concentrations: i.e. ...read more.

Middle

Measurements: To collect reliable/precise/accurate measurements certain principles must be adhered to. 1. When shaking the flask try to be consistent throughout the experiment to minimise variation in shaking. 2. Try to keep the delivery tube free of water and keep the same amount of tube underwater each time you take a measurement to prevent more/less oxygen coming through due to water 3. Use pH buffer to keep the pH the same throughout the experiment. Control Variables: Temperature will be monitored at all times using a thermometer. It did was seen not to vary during the course of the experiment so no further control was needed. pH was controlled by a buffer at pH7. Substrate was always the same volume and in excess Preliminary Data: We had to decide on the ratio of enzyme/pH buffer:Hydrogen peroxide. Our preliminary data showed us that 5:7 worked best because the time taken for the catalase to react with the hydrogen peroxide started to slow down just after 20 seconds, this also gave us the time which we would collect the oxygen for. Enzyme (cm�) H202 (cm�) Gas collected in 30 seconds (cm�) 5 5 53 5 7 57 5 10 59 3 5 36 3 7 41 3 10 45 Here the table shows us that using 5:7 gives us nearly 60 cm� in 30 seconds, undocumented ...read more.

Conclusion

A gas syringe would be a very accurate way of measuring and would be the best way to carry out the experiment. Anomalous results: Test 3 had a result 5cm� difference from the other recordings, I believe this to be anomolous and due to a large amount of water in the delivery tube. At 20% concentration the results were variable 7,10 and 13cm� this is a mean of 10cm� which may be accurate but not precise. I beieve this again was due to water in the delivery tube with the low pressures the gas output variaed a lot because each time the repeat was carried out there was a different amount of water in the delivery tube. Conclusion: I am confident in saying that the relationship between catalase and hydrogen peroxide shows a positive linear correlation. My data was reliable as shown by the very small spread in the range bars and accurate as all points are close to the line of best fit. I am also sure that by using a gas syringe the experiment would produce even more accurate results, but even this experiment has proved that increasing enzyme concentraion increases the rate of reactions. ?? ?? ?? ?? Candidate Name: Will Price Candidate Number: 2485 Centre Number: 24315 The Relationship between catalase and hydrogen peroxide ...read more.

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