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To find the effect of the enzyme concentration on the reaction between Catalase and hydrogen peroxide.

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The Effect of Enzyme Concentration on the Reaction Between Catalase and Hydrogen Peroxide Aim To find the effect of the enzyme concentration on the reaction between Catalase and hydrogen peroxide. Background Knowledge and Variables (Cambridge Advanced Sciences; Biology 1and Chemistry 1, www.coursework.info) An enzyme, a biological catalyst, accelerates a chemical reaction without changing the reaction's outcome and can be recovered from amongst the end products. For just about every reactions in a living organism there is an enzyme to catalyse it. For chemical reactions to occur, two conditions must be obtained: the reacting molecules collide successfully and that this collision must have enough energy to produce a reaction to break the bonds, which need to be broken. The energy can come from heat but a high temperature is had to control and can be harmful or impractical for the other reactants which are present. Enzymes are globular protein molecules. They are made from protein produced by living cells. A protein molecule is made of polypeptides that are a series of amino acids linked together by peptide bonds. They can be made up of different configurations of polypeptide chains. There are secondary, tertiary and quaternary structures (i.e. haemoglobin) protein molecules which increase respectively in complexity. Proteins contain an 'R-group' which is specific to each amino acid, this part of the molecule is the active site. Enzymes lower the activation energy needed for chemical reactions and allow the reactions to occur rapidly at the relatively low temperature of living things, without enzymes the high metabolic rates in organisms would not exist. An enzyme decreases the activation energy so that the substrate molecules have energy greater than, or can easily reach the new activation energy and therefore the rate of reaction increases. For this to occur the catalase molecule must collide with the Hydrogen Peroxide molecule in the correct place (active site) for the collision to be successful and produce the products. The random movement of the molecules in the liquid solution results in these collisions. ...read more.


2. Get all the apparatus and lay it out in front of you and check you have it all. 3. Fill the water bath with water from a nearby tap until it is 3/4 of the way full. 4. Make sure that the beehive shelf will be completely emmersed in the water and allow 1/2cm to slide the measuring cylinder on top. 5. Take the delivery tubing and feed it under the beehive shelf until it pokes out the hole in the centre slightly. (the non-bung end) 6. Take the measuring cylinder and sill it right to the top, put your hand firmly over the top and place the mouth of the measuring cylinder, along with your hand, underwater. Once underwater you may remover your hand. In this stage try not to let any bubbles into the measuring cylinder. 7. Carefully slide the measuring cylinder over the top of the delivery tube and rest it on top of the beehive shelf with the end of the delivery tube in the middle of the opening of the measuring cylinder. 8. Fix the measuring cylinder in place using the boss and clamp. Try and fix the measuring cylinder directly upright otherwise your readings may be slightly inaccurate. 9. Make sure that there are no bubbles in the measuring cylinder. 10. Take 6 boiling tubes and label them 10, 8, 6, 4, 2 and 0 which corresponds to the liver homogenate concentration 11. Fill the designated syringe for the hydrogen peroxide with 5cm3 from the hydrogen peroxide beaker. Make sure that there are no bubbles. 12. Label the syringe 'hydrogen peroxide'. 13. Add this hydrogen peroxide to the boiling tube labelled '0' 14. Suck up 1cm3 of water in the syringe (no bubbles) 15. Label the syringe 'Water' 16. Take the bung on the end of the delivery tube and place it part way across the opening of the boiling tube, with the syringe ready pointing into the boiling tube in the other half. ...read more.


I I had used a 5cm3 syringe to measure all the soultions I would have been able to read these to �0.025cm3 which is only a �2.5% percentage error. For each repeat that I did, the experiment was �55% accurate which is quite poor. Alternatively I could have used a gas syringe or a burette to measure the volume of oxygen collected, which would have been more accurate and given me better results. None of my results are anomalous. This might be because the same bad effects might have happened on every repeat, therefore all the results would have been affected and shifted in the same way, or that the apparatus that I used was secure. A major source of error is the sample preparation and maintaining the solutions as they can decay over time. It would have been better if the hydrogen peroxide and the liver solution were kept in a water bath and keep the hydrogen peroxide out of the sunlight as it can be decomposed by UV light. The liver homogenate may have also had some impurities in it which may have affected my results, or there may have been a difference in sixe in the bits of liver floating around which would slow the reaction down if the bits were larger as a reaction can only occur on the surface of a solid. There is no way to really overcome this unless you really make sure that all there are no liver bits present. I could not start the timer and squirt the liver into the hydrogen peroxide at the same time therefore the timing was a bit inaccurate. I would have been better if I had ha d a partner to start the stop clock for me once the liver was introduced to the hydrogen peroxide. This may have improved my results slightly. Seeing as rates of reaction are so sensitive to temperature I still would have liked to have used a water bath during this experiment as this would have regulated the temperature. Hannah Davenport 1 ...read more.

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