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Investigation into the effect of enzyme concentration on the rate of hydrogen peroxide breakdown.

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Investigation into the effect of enzyme concentration on the rate of hydrogen peroxide breakdown. Introduction Enzyme - any group of complex proteins produced by living cells and acting as catalysts in biochemical reactions The brothers Hans and Eduard Buchner, who were at the time studying yeast for medical purposes, discovered enzymes in 1897. Enzymes are essential to all living organisms, as they act as catalysts to allow chemical reactions to take place within cells at low temperatures, usually between 4�C and 60�C. They do this by lowering the energy needed to start a reaction, this is known as 'activation energy'. Enzymes attach to substrate becoming enzyme substrate complex. They then alter the enzyme substrate complex into product and an enzyme. The enzyme is unaffected in the process and is then ready to accept more substrate. Enzymes have a specific tertiary shape that allows only a specific substrate to fit into the active site. The active site is the area of the enzyme that the substrate binds to be altered into product. enzyme + substrate enzyme substrate complex product + free enzyme An example of this is the enzyme 'catalyase'. This enzyme is essential to organisms as it converts hydrogen peroxide into water and oxygen. Hydrogen peroxide is formed in the cell as a by-product of biochemical activity and it can be toxic to cells and cell organelles in the organism. catalyase H2O2 H2O + 02 Hydrogen peroxide enzyme water oxygen Substrates will only react with specific enzymes to form product. This is shown in Fischer's lock and key theory and in Koshlands induced fit theory. ...read more.


Graph 1.8 shows the results from the second batch of tests. With four discs it gave off 31 bubbles increasing to 156 bubbles with twenty discs. Graph 1.8 Effect of increasing enzyme concentrations. Batch 2. Graph 2.0 shows an average of the two separate rounds of tests. The average figures should show a more accurate representation of what the data should read if everything during the experiment had been kept at an exact constant, with no abnormalities, except the independent variables. Graph 2.0 Effect of increasing enzyme concentration. An average taken from test batches one and two. The numbers of bubbles given off in the first round of tests were all higher than the second round of tests. With four potato discs, round one gave off thirty-nine bubbles but the second round gave only thirty-one bubbles. With twelve potato discs round one gave one hundred and five bubbles but round two only gave ninety-two (results cont.) bubbles. In the twenty potato disc size test round one gave two hundred and forty-six bubbles and round two gave one hundred and fifty six. Fifty percent of the result figures were in line with the proportionate rate of product formation to enzyme concentration increase, and the other fifty were out of line with the rest. To be in line I allowed a five-percent tolerance level for the actual figures. This is to allow for the uncertainty of actual bubble gas volume. Of those four figures that were out of the proportionate rate three were higher than the proportionate rate and one was lower. ...read more.


If there was any variation in temperature from test to test then the test with the warmer solution might have increased results due to the extra kinetic activity the increased heat would cause. 4) Temperature control of the potato. If there were any areas of the potato which were warmer than others then they might be prone to a accelerated rate of denature of decomposition from a cooler area. This might lead to anomalous results because of uneven enzyme distribution. 5) Whilst the tests were being run I noticed that the potato discs all floated to the top of the hydrogen peroxide solution. This might have effected the results by some areas of the enzyme not being in any contact with the substrate. To alleviate this problem a shaker could be included to the apparatus to gently rock the test tube holding the H2O2 and catalase to ensure constant circulation of the products. 6) Replacing the potato discs with an homogenate of potato or by using a liquid catalase. Cutting the potato discs 1cm x 0.2cm is a little too precise with a scalpel and ruler, and is prone to irregular cutting, which may cause anomalous results by having a different surface areas from discs to discs, batch to batch. 7) When measuring the 10cm� of hydrogen peroxide out into the test tube I used a 5cm� twice. It would be more accurate to use a 10cm� pipette or cylinder. 8) During the practical I put the hydrogen peroxide into the test tube first then cut the potato. This would be altered to putting the potato in first, as hydrogen peroxide is susceptible to degradation by air and sunlight. This may have weakened the solution and caused anomalous results. ...read more.

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