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The Effect of Substrate Concentration on the Rate of Decomposition of Immobilised Liver Catalase.

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Introduction

The Effect of Substrate Concentration on the Rate of Decomposition of Immobilised Liver Catalase Background Information: When the chemical Hydrogen peroxide (H2O2), is introduced to the enzyme Catalase, it is decomposed into to products, Oxygen (O2) and Water (H2O). This is shown by the equation: 2H2O2 (l) 2H2O (l) + O2(G) AIM: I am aiming to find out whether increasing the concentration of substrate (H2O2) affects the rate at which Oxygen is produced from the decomposition reaction. I will do this by counting the number of bubbles of Oxygen produced from several samples over a set period of time. I have established that: The Independent variable = Substrate concn The Dependant variable = Production of O2 The variables: The variables that have to remain constant are: * Concentration of catalase (5% liver extract) * Volume of Hydrogen Peroxide * PH * Temperature (controlled by water bath) * Time (2 min. period p/experiment) PLANNING I am going to be changing the concentration of H2O2 that the beads of catalase will be added to (making it an immobilised enzyme). ...read more.

Middle

* When you have used up all of the mixture, with a sieve collect the beads and rinse them off with a little distilled water. METHOD: 1. Set up apparatus shown below: 2. To make the desired concentration of hydrogen peroxide, get a 10ml measuring cylinder and for 10% place 1ml of hydrogen peroxide in with 9ml of distilled water. (CARE: Hydrogen peroxide is an irritant, keep away from eyes and clothes, as bleaching can occur.) 3. Then place 20 beads into the boiling tube of Hydrogen Peroxide and insert the bung of the delivery tube back in and start the timer. 4. Over a period of 2 mins. Count the number of bubbles produced from the reaction. 5. After, repeat the experiment with 20% and 30% concentrations. 6. When gaining the results for all three concentrations, do three repeats per concentration to gain reliable results. RESULTS: This graph shows the relationship that is present between the results. As the concentration of Hydrogen Peroxide is increased (coloured bars) the amount of Oxygen increases also. The concentration that was most effective on oxygen production was 40% (dark purple), with roughly around 140 bubbles produced in 2 minutes. ...read more.

Conclusion

Because all enzymes are proteins, they are consisted of amino acids, and when these long chains fold up the form an active site, which then can react with substrates. If too much heat energy is added, the molecule is vibrating with such energy that weak Hydrogen bonds that hold the tertiary structure of the protein together are broken. These results in reshaping of the active site, that is very specific to certain substrates, and therefore becomes denatured. Although increasing the concentration of the substrate increases the rate of decomposition, if the concentration is increased too much the active sites on the enzymes will be saturated (occupied by substrates), this would then decline the rate at which Oxygen was produced. I think the results that I gained show a clear trend forming from reliable results. If I were to repeat this experiment again I would like to prove whether what I can tell with my own scientific knowledge, that if I carried on increasing the concentration of Hydrogen Peroxide to a point where there were more substrates than enzymes, I would see a gradual decline in the amount of oxygen produced. If I carried out such an experiment I would expect to see the pattern on the graph to look like this: ...read more.

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