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An Investigation Into How Temperature Affects The Rate At Which Yeast Catalase Catalyses The Decomposition Of H O

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Introduction

An Investigation Into How Temperature Affects The Rate At Which Yeast Catalase Catalyses The Decomposition Of H O Aim: To Investigate how temperature affects the rate at which catalase catalyses hydrogen peroxide. Apparatus And Materials: 20cm 5 % yeast solution 2gs yeast 40cm warm water 1 small (50ml ) beaker Metal spatula 50cm hydrogen peroxide (H O ) 1mo/dm Stopwatch Gas syringe 100cm conical flask 2 x 5cm syringe 2 test tubes Thermometer Clamp 500cm glass beaker Measuring cylinder Balance Bunsen Burner Tripod Gauze Heat Proof Mat Method: 1) Set up the apparatus as shown above, put on apron and safety goggles. 2) Take the 2gs of yeast and add to the 40cm of warmed water in the small beaker, stir using the metal spatula and leave to stand for a minute. 3) 2cm of the yeast solution should be measured out using a 5ml syringe and placed in 1 of the test tubes, 5cm of the H O should be measured out using the other 5cm syringe and placed in the other test tube. 4) Then place both test tubes and the empty conical flask in the water bath, and heat over the Bunsen burner, checking the temperature on the thermometer until the right temperature has been reached 5) Keep the temperature steady for 2 minutes by removing the heat (if it drops dramatically, heat again) to allow the test tubes to remain at a constant heat 6) Take out the warmed conical flask, pour the yeast solution from the test tube into the warmed conical flask, then add the H O and quickly place the bung into the neck of the conical flask and start the stopwatch 7) ...read more.

Middle

High temperatures cause enzymes to denature. They cause the large complicated protein chains to unravel and change shape permanently. The substrates will no longer fit the active site and the enzyme will not work. Enzymes are proteins and their structure is three-dimensional. Increasing the temperature beyond a certain point disturbs the hydrogen bonds that hold the 3D shape, and alters the shape. This alters the active site so the substrate will no longer fit in and so the enzyme will not work properly. Yeast is used most commonly in breweries, because they are unique to all living organisms in that they contain the extra enzymes that allow for fermentation. One enzyme that it contains is catalase. Catalase is used for applications where hydrogen peroxide has to be removed, such as in contact lens cleaning systems, for bleaching of textiles and hair, and in industrial processes that generate hydrogen peroxide. One molecule of catalase can break 40 million molecules of hydrogen peroxide each second. My predicted graph shows a rising arm, which means there is increased molecular activity within the solution, producing larger amounts of O . This is due to the increase in temperature, relating to the kinetic theory. The higher the temperature, the faster the particles move. The graph shows this happening to an optimum of 40�C. The curve leading up to the optimum point is gradual but as it is reached it falls dramatically. I think this is because the active site is destroyed therefore no reaction can take place. Results: Table To Show The Amount Of Oxygen Given Off At The Different Temperatures Temperature ( C) ...read more.

Conclusion

There is always human error to account for when it comes to starting stop watches, putting bung sin etc. because of differing reflex times, ideally it would be done with a machine which could be programmed exactly, but this is not feasible for a secondary school experiment. To improve accuracy in the amount of solution used, more care should be taken when measuring it out, to ensure that no air bubbles appear. Recording the amount of O given off sometimes causes inaccuracies if the number is not read correctly from the gas syringe, the divisions (cm ) are suitable for this experiment, but to be especially sure, a photograph could be taken at exactly 30seconds, to record where exactly the gas syringe was. Two repeats were taken, ideally there would be 3, to ensure the most accurate line of best fit. The range of readings taken is also something I would change, I would do more temperatures, I feel that the ones used were not accurate enough, for example I would also record 25, 35, 45 C etc, this would give more accurate and reliable results, and eliminate big gaps in the graph. I believe the apparatus we used was appropriate and suitable for the experiment. To further support my conclusion, I would look into the amount of froth given off when the H O was mixed with the yeast, I hypothesize that this would increase as the catalase reaches its optimum temperature, and then decrease as it denatures. This could be done with larger amounts of solutions, and perhaps video recording equipment, to record the experiment, as it seems to occur fairly quickly. . ...read more.

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