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An Investigation into the Catalytic Action of the Enzyme Peroxidase

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Introduction

An Investigation into the Catalytic Action of the Enzyme Peroxidase The enzyme peroxidase acts as a catalyst for decomposing hydrogen peroxide into water and oxygen. The equation for this is: 2H2O2 (aq) -->2H2O (l) + O2 (g) For this investigation fresh liver extract is used as this contains the enzyme peroxidase. The liver extract will be reacted with hydrogen peroxide and the peroxidase will act as a catalyst to speed up the reaction, producing water and oxygen. The oxygen will be collected as a measure of the rate of the reaction. To find the rate of reaction I will measure the amount of O2 cm3 and divide that by the time taken for each amount of oxygen to be produced. APPARATUS I think that the following apparatus is going to be the most suitable and reliable for the investigation: Conical flask with rubber bung tub of water Syringe Glass tubing Measuring cylinder SAFETY It is critical for safety levels to be maintained at a high standard throughout the investigation. It is important to be careful when dealing with hot water and liver extract. ...read more.

Middle

VARIABLES The factors that can affect the rate of reaction are: The temperature of the liver extract and hydrogen peroxide The concentrations of the reactants The concentrations of the reactants have to be the same throughout the investigation or else the test is not fair. The collision theory tells us that there is going to be a greater reaction (more oxygen produced) if there is a greater concentration of reactants. The quantity of the reactants Again using the collision theory I can tell that the greater the amount of reactants the larger the quantity of oxygen will be produced. Therefore it is important that the quantity of the reactants is kept the same throughout the tests to ensure a fair investigation. PREDICTION I think that the rate of catalytic reaction will increase in line with the increased temperature of the liver extract. This should occur because the higher the temperature of the liver extract the faster the peroxidase enzyme molecules move and the greater the chance of them colliding with the hydrogen peroxide molecules. Slower moving Faster moving Molecules molecules (less chance of collision)(Greater chance of collision) ...read more.

Conclusion

My prediction was proved by my results It is inevitable that not all of the oxygen in the final measuring cylinder will have been given off in the reaction because there will be a small amount of oxygen in the conical flask at the start of the investigation. The amount of liver extract used in the reaction will be slightly smaller than the original amount at the beginning of the investigation as some (1cm3)will remain in the end of the syringe. I have recognised both these factors, but as they occur consistently in each test I feel they did not effect my results. The small amount of oxygen collected when the liver extract was heated to 500C may have been due to oxygen already in the conical flask. If I had more time to perform the investigation I would have tested to find out more accurately at what temperature the peroxidase stopped working and died. It was not necessary to my knowledge to repeat any tests. This was because my concentration was maintained throughout the experiment. I also worked out how I could prevent oxygen getting into the measuring cylinder before the reaction took place. This made calculating the amount of oxygen gathered much simpler and gave less room for errors. ...read more.

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