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The effect of temperature on an enzyme controlled reaction

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The effect of temperature on an enzyme controlled reaction Introduction For this investigation I have been asked to investigate the effect of temperature on the rate of decomposition of the substrate hydrogen peroxide when catalysed by the enzyme catalase. The substrate hydrogen peroxide is a naturally produced substance, it is generated as a toxic by-product from the liver and by cell metabolism. Hydrogen peroxide, H2O2, is also produced by white blood cells as a means of killing bacteria. If the HzO2 is not broken down and left to accumulate it can be very serious as it will intoxicate the cells. This is why an enzyme is needed to catalyse the reaction, otherwise hydrogen peroxide would decompose far too slowly, the enzyme being catalase. All biochemical reactions need enzymes to catalyse the reaction, examples of enzyme-aided reactions include all digestion and growth. If there is any chemical reaction in any living thing there is an enzyme helping. Enzymes are made up of a complex of amino acids. The way the enzyme catalyses the reaction is by reducing the amount of energy needed, in essence it provides an alternate path of energy for the reaction, hence it merely speeds up the reaction. ...read more.


Preliminary work During my preliminary work I used the same method that is described further below. At first I found that using 5 cm3 of yeast and 5 cm3 of hydrogen peroxide was far too much as it kept on overflowing and that 0.5 cm3 of each is very sufficient. I found out that you must ensure the bung is properly secured onto the test-tube otherwise the oxygen is released out. I learnt to be more cautious when setting up the apparatus and making sure that there were no air bubbles trapped in the syringes, for accurate measurements. Once I found the correct measurements I should use I did the experiment and found some results at 100C, which I have included in my table of results further down Apparatus 500ml beaker Some plasticine 10ml calibrated syringe 2x1ml syringe Stopwatch 6xTest tubes 2xsmall beaker Test tube rack Delivery tube Water bath at 10?C, 20?C, 30?C, 40?C, 50?C, 60?C Diagram Method 1. Set up the apparatus as above. 2. Fill 10ml syringe with water and submerge in the beaker, ensuring no air bubbles are present as this could affect your results. 3. Make sure the yeast and hydrogen peroxide are heated up to the temperature being investigated, e.g. ...read more.


I think the reason there were a few slight anomalies was maybe because of slight misreadings or small impurities in the equipment used. Another reason could be that a small amount of oxygen escaped before the bung was put on, or even that if the bung was pushed on very hard a small surge of oxygen could have been pushed into the measuring syringe. Looking at the tables of results some readings for the same temperature seem to have large differences between them. This could be because not all the yeast was properly poured into the hydrogen peroxide test-tube. A major fact that could have affected my results might have been that even though hydrogen peroxide decomposes very slowly, there is still some gradual break down, especially when left in the light in a clear beaker - which is what happened. Overall I personally think the experiment went well, my hypothesis was right, the method worked, and especially considering that it was all performed under school lab conditions. If I had the opportunity to do the experiment again I would try to use more restricted lab conditions. I would try to measure the volume electronically with an electronic counter. Possibly do the experiment in a thermostatically controlled environment. ?? ?? ?? ?? Sean Verrall 28/04/07 1 ...read more.

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