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An Investigation into the Effect of Temperature on an Enzyme Catalysed Reaction.

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Introduction

An Investigation into the Effect of Temperature on an Enzyme Catalysed Reaction. The aim of our investigation is to show how various temperatures affects the rate at which oxygen and water are produced in the catalysed reaction of Hydrogen Peroxide. The catalyst we are going to use is found naturally occurring in potato. Background Information: Enzymes can be divided into two main groups, intracellular and extracellular. Intracellular are found inside the cell, from where the control metabolism. These cells will also produce the extracellular cells, but these achieve their affect outside the cell. These include digestive enzymes that break down food in the gut. An enzyme is named by adding the suffix - ASE to the substrate, which it acts upon. Hydrolase's catalyse the hydrolysis of a substrate by the addition of a water molecule. Oxoreductases are involved with redox reactions. Transferases transfer a group of atoms from one molecule to another, and so on4. Enzymes are complex globular proteins, folded up into a precise 3d shape. They are made from a long polypeptide chain, which in a globular protein is wound and folded into a precise spherical shape. Hydrogen, ionic, disulphide bonds as well as hydrophobic interactions all hold the chain in its three dimensional shape. The precise shape of the active site, the place at which the substrate is to bind, is so because the enzyme is specific to one substrate, hence the need for specificality. Thus meaning that the active site of an enzyme has a distinct chemical configuration to which only one substrate has the correct and complementary chemical configuration. This is known as the ' lock and key' hypothesis. An enzyme works by combining with the substrate molecule to form an enzyme - substrate complex. With their various bonds held into relation with each other, the substrate molecule then reacts to form the enzyme - product complex. This then splits into the enzyme and product(s). ...read more.

Middle

We found that the best pH to use was 7. After five minutes of reacting 75 ml of hydrogen peroxide and 2cm2 of Catalase in this condition we found that a yield of 10.10ml of oxygen was produced. This was the greatest amount. We also compared it to pHs at either end of the spectrum. At pH 4 we found that 7.10ml were produced and at pH 10 9.00ml was produced. This is what we expected to see, as when researching the enzyme Catalase we found it worked best under neutral conditions. Temperature: we decided to look and see what the optimum temperature would be, just so we were aware when the maximum amount of oxygen should be produced. We thought it would be about 40oC. This is because in the body, the temperature is kept at about this, and as Catalase is found in there it must be about this point. After five minutes of reacting 75 ml of hydrogen peroxide and 2cm2 of Catalase in this condition we found that: Temperature in oC Amount of O2 produced in ml 20oC 10.50ml 40oC 16.00ml 60oC 8.50ml 80oC 7.00ml This confirmed what we thought and so know knew to look out for the maximum being at 40oC. This test also showed us that we needed a bigger range of temperatures and to have many repetitions to get the best results we can. Concentration of Hydrogen Peroxide: We also looked in which concentration of Hydrogen Peroxide gave the best amount of oxygen produced. We found that after five minutes of reacting 75 ml of hydrogen peroxide and 2cm2 of Catalase in this condition: Concentration in Vol. Amount of O2 produced in ml 5 Vol 5.00ml 10 Vol 9.00ml 15 Vol 13.00ml 20 Vol 14.00ml From this we could see that the best concentration to use was 20 Vol. We decided in the end though to use 15 vol. ...read more.

Conclusion

Using a weighed amount of powdered Catalase. You then have a precise amount of Catalase and so reduce the margin of error. The apparatus used. In the different repetitions it may have been possible to pick up a slightly different set of equipment. To standardise the equipment used and ensuring the same equipment is used each time. Reduces the margin of error. For example if the length of the delivery tube varied between experiments, then the amount of oxygen recorded could be affected. Amount of Hydrogen Peroxide used. The measuring cylinder it was collected in was an approximation. Using a pipette or to titrate an even more precise amount. The amount of hydrogen peroxide would vary the substrate concentration. This means that the amount of oxygen collected may vary, incorporating errors. The accuracy and way of collecting the gas, collecting it in an upturned measuring cylinder. Smaller graduations on the cylinder or a gas syringe. It would give the amount of gas produced to a nearer degree of accuracy, meaning the overall results will be more reliable and accurate. The cutting of the potato, with a knife and borer. Cut with a guillotine set at right angles. If the potato was cut wonky, the surface area would be increased. This would increase the amount of enzyme and not give an accurate and reliable result. The fact that the temperature in the room fluctuated Using a room that has air conditioning, so the room temperature can be set and maintained. If the room temperature changes it will not only affect the temperature of the water baths and hydrogen peroxide, but will also affect the potato and the enzyme within it. Moistness of the potato Weigh the potato and calculate my mass rather than size Drying the potato off with a piece of towelling may take away some of the enzyme. Size and shape of potato Weigh the potato and calculate my mass rather than size This would effect the amount of enzyme present thus changing the amount of oxygen produced. 4 2 http://crystal.uah.edu/~carter/enzyme/catalase.htm 3 www.schoolscience.co.uk/.../ catalysis/catsch8pg1.html Rebecca Worley Biology ...read more.

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