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Investigating the effect of temperature on the rate of enzyme action

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Introduction

Investigating the effect of temperature on the rate of enzyme action Background Hydrogen Peroxide is a toxic substance which until the twentieth century, had no practical use. It is seldom created in its pure form because it explodes when it comes into contact with many everyday substances. This explosion is a decomposition of the hydrogen peroxide into water and oxygen and is the reaction that I shall be testing in the experiment. Hydrogen Peroxide can be found naturally as a by-product of certain bio-chemical reactions. Some of these reactions take place in the liver and so there is catalase in the liver to break it down before it can do any damage to the liver. Today it is diluted and often used as a bleaching agent. (Encyclopaedia Britannica) Catalase is an enzyme found in the human liver for the purpose of decomposing any hydrogen peroxide, which may be formed as a by-product of some of the reactions taking place there. The catalase breaks down hydrogen peroxide into it's constituent parts, hydrogen and oxygen. Catalase is the fastest acting enzyme known, with a turnover number of 6 million (being the number of substrate molecules the enzyme can act upon in one minute. Turnover numbers range from as few as 100 up to 6 million). (Understanding Biology for Advanced Level by Glenn & Susan Toole) Prediction As the temperature increases then so will the rate of the enzyme action up to 40oC. Above 40oC the rate of reaction should steadily drop until in reaches 50oC. At this point, the enzymes will become de-natured and the reactions will stop. The optimum temperature for enzyme action is just below 40oC and so this should be the place where the most oxygen is produced by the reaction. Hydrogen Peroxide Water + Oxygen Catalase 2H2O2 2H2O + O2 This is because enzymes are made up of proteins and these are sensitive to temperature changes. ...read more.

Middle

The concentration of the hydrogen peroxide that should be used is 2 moles. 4. Place the hydrogen peroxide into the boiling tube and put the tube into the water filled beaker. 5. Allow 2 minutes for the hydrogen peroxide to warm up to the required temperature. 6. Add the potato to the hydrogen peroxide and seal the top of the flask with the bung so that the oxygen has to travel along the tube and enter the upturned measuring cylinder. 7. Time for four minutes and then stop the experiment. 8. Measure the amount of oxygen that has collected at the top of the measuring cylinder and record the measurement on the table. 9. Repeat this two more times and then take an average of the amount of gas collected. 10. Repeat steps 1-8 with temperatures of 30oC, 40oC, 50oC, and 60oC. 11. Repeat the experiment three times at each temperature. Results Temperature of Water (oC) Volume of Oxygen produced in 120 seconds (cm3) Average volume of gas produced (cm3) Rate of enzyme action: (cm3/s) Average Volume Time 1 2 3 20 10 13 12 11.67 0.0486 30 12 14 13 13 0.0542 40 16 15 15 15.33 0.0639 50 14 11 13 12.33 0.0528 60 6 5 3 4.67 0.0194 As the rate of enzyme action was very small, I decided to scale the number up by a factor of 1,000. This will make it easier to do any calculations that may need to be done. Rate of enzyme action: Average Volume Time (cm3/s) Rate of reaction scales up by factor 1,000 (cm3/s) 0.0486 48.6 0.0542 54.2 0.0639 63.9 0.0528 52.8 0.0194 19.4 Conclusion The graph shows that there is a direct correlation between temperature of the catalase and the amount of rate of the reaction when it is added to hydrogen peroxide. The x-axis shows the temperature of the enzyme for each experiment and the y-axis shows the rate of reaction of the enzyme at each of the temperatures. ...read more.

Conclusion

Any changes in pH would change the rate of reaction, so a buffer would be used to would keep pH constant. * Whilst I was conducting the experiment, there was a time lapse between when I first added the potato to the hydrogen peroxide, and when I placed the bung with the tube in it onto the boiling tube. To overcome this, I could either syringe the potato into the solution or put it into a test tube which would 'rot' and release the enzyme into the hydrogen peroxide. Both of these solutions would stop any oxygen produced being let out before the bung can be added. * To make the experiment a more accurate reflection of the way temperature affects the rate of enzyme action, I could use catalase extract. During the experiment, the catalase was part of a potato. This would have affected the results because some of the enzyme would have still been trapped within the cells, unable to react. Even though I liquidised the potato, there would still have been a lot of catalase which would not have reacted with the hydrogen peroxide. Using catalase extract would solve this because none of the catalase would be trapped and all of it would be free to react with the hydrogen peroxide. Extending the Experiment * To extend the experiment, I could try using different enzymes. In the experiment, I was only testing whether temperature affected the rate of one enzyme, catalase. To find out whether temperature affects all enzymes, then I would have to use many different enzymes or else it would not be a fair test. * I would also have to test as to whether the enzymes only affected hydrogen peroxide. I would have to use many other substances, such as those found in the human body, to find this out. * To make sure that there were no 'freak' results within the data, I could also repeat the experiment more than three times. This would mean that it would be much harder for any errors to show up in the results. * * * * ...read more.

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