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Investigation to study how temperature affects the activity of an enzyme.

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Investigation to Study how Temperature Affects The Activity of an Enzyme Introduction: Substrate Concentration When the concentration of substrate is low collisions between the enzyme and substrate molecules are infrequent and reaction proceeds slowly. As the substrate concentration increases, the rate of reaction increases proportionately as there are more collisions between the two reactants. When the enzymes begin to approach the maximum rate at which they can combine with reactants and release products, the effects of increasing substrate concentration lessen. When enzymes reach the point where they are reacting as quickly as possible an increase in substrate concentration will have no effect. At this point the enzyme is saturated and the reaction remains at the saturation level. Bearing in mind the above information I predict that as the level of catalase is increased (i.e. the volume of potato) the rate of reaction will increase up to the enzymes saturation point, which can only be found by performing the experiment. Enzymes are biological catalysts. They speed up reactions in living things. They are made from proteins and enable vital biological reactions to take place and therefore support life. Each particular enzyme has a 3-dimensional shape/surface. Within this shape there is an area called the active site where the chemical reactions occur. Enzymes work best under certain conditions and these are known as optimum conditions. Each type of enzyme has its own conditions and as the conditions of the reactions change it affects the rate of reaction. The enzyme used in this investigation Catalase is the fastest working enzyme known to man which is very useful for this experiment as it is more likely to yield larger readings which are easier to measure than smaller ones. ...read more.


* It was discovered that there was a time lag for the H2O2 to reach the temperature of the water bath, of about 20-30 seconds; therefore before the potato is added the H2O2 will be placed in the water bath for 30 seconds. * 10ml of H2O2 was used in the preliminary experiment but produced little oxygen; therefore it was doubled which doubled the substrate volume in order to increase the rate of reaction. * At first a gas syringe was to be used to measure the oxygen produced but the gas produced wouldn't exert enough pressure to move the syringe and so the gas displacing water method (as shown in the diagram) was used Safety: * Hot water will be used and so the experiment will have to be performed standing up with hair ties and shirts tucked in. * Hydrogen Peroxide is HARMFUL and must be handled with care; safety glasses must be worn at all times. * Knives will be used and therefore it is imperative that a sensible nature is adopted to ensure a safe practical. Fair Test/Controlled Variables: * PH level: - the same amount of hydrogen peroxide will be used 20ml for each experiment and the pH level will be the same as it will all be from the same bottle * Substrate Concentration: -The same amount of H2O2 will be used, as is all of the same concentration as it came from the same bottle. * Enzyme concentration; - assuming that the enzymes are spread evenly throughout the potato, gain a compromise between making sure there are no inaccuracies due to the catalase leeching out of the potato into the H2O2 and keeping the same amount of enzyme/potato constant by changing the potato pieces for every new temperature. ...read more.


As a result not all the oxygen that was produced was collected. * The time lag of thirty seconds was obviously not enough to warm the H2O2 to the water bath temperature and the fact that we couldn't warm the actual enzymes in the potato to the water bath temperature before the potato was added allowed the enzymes to react at high temperatures before they actually reached the water bath temperature themselves and were denatured. This was shown in the last three measurements in red on the results table (which should have been nil) where temperatures above the denaturation point should have caused the enzymes to denature. However there was a time lag before the enzymes could reach that temperature and therefore they reacted with the H2O2 during that time lag. * As stated in the 'Preliminary Conclusion Notes and Changes to the Method' we were not able to use gas syringes and measuring cylinders were used. The scale on these was poor and readings had to be approximated to the nearest half a cm3 which caused inaccuracies in the results. However as stated before these sources of error occurred in all the experiments and therefore the results are at least relative to eachother if not fully accurate. As shown in the extension to the methodology further work was proposed and carried out to find the optimum temperature for catalase, which was 46o. However if I wanted to further my investigation even more I could investigate more temperatures and conclude whether catalase stops reacting or slows down at a certain temperature, perhaps below freezing when it is harder for the molecules to move around. 02/05/2007 Page 1 Djamiel Lowhar-Malcolm ...read more.

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