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Enzyme concentration and rate of reaction

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Introduction

DOES ENZYME COCENTRATION AFFECT ENZYME ACTIVITY? PLAN The aim of the following experiment is to determine whether amount of enzyme concentration affects the enzyme activity in an enzyme catalysed reaction. Hypothesis Enzyme concentration affects enzyme activity. If this is so, then we should expect a correlation, either positive or negative, between the enzyme concentration and the rate of reaction. Activation energy is needed by every reaction to occur. A high enzyme concentration inevitably increases the rate of reaction. There is a directly proportional ratio (positive correlation) between the two, until a peak rate of reaction occurs where the rate cannot increase any further. This will produce a straight-line graph through the origin, which will eventually flatten off at peak rate. Scientific Background An enzyme is a class of protein, which acts as a biological catalyst to speed up the rate of reaction with its substrates. Enzymes have the ability to act on a small group of chemically similar substances. Enzymes are very specific, in the sense that each enzyme is limited to interact with only one set of reactants; the reactants are referred to as substrates. Substrates of an enzyme are the chemicals altered by enzyme-catalysed reactions. The extreme specific nature of enzymes is due to the complicated three-dimensional shape, which is due to the particular way the amino acid chain of protein folds. ...read more.

Middle

4. Any oxygen given off will collect in the burette. The oxygen given off indicates that a reaction is taking place since H2O2 is decomposed to form water and oxygen gas. This gas can also be tested further by placing a glowing splint into the gas and it will catch fire. 5. Once an observable volume of oxygen gas has be produced, read off how much oxygen was produced. 6. This is repeated 3 times to ensure reliable results. 7. The whole experiment is repeated for 2,3,4 and 5 disks Changes to experiment. 1. Time taken for 2cm3 of oxygen to be produced was recorded to make results fair. 2. Only experiments for 1,2,3,4 disks were carried out since time to carry out experiment was limited. 3. Each experiment was also carried out twice since time wasn't enough. Controlled Variable The controlled variable is the factor that I will keep constant throughout the experiment. In this case the controlled variables are: the volume of Hydrogen Peroxide, temperature, timing, pH and substrate concentration. In order to obtain a fair test, the following factors need to be controlled: 1. the pH - The pH can slow down the enzyme hydrolysing the substrate. Extremes of pH can denature the enzyme so the reaction would not proceed. This will lead to an unfair test if not controlled, and experiment would produce very strange results. ...read more.

Conclusion

3. Rate of reaction was at its lowest when only 1 disc was placed in the H2O2 solution, as it took 47.971 minutes for H2O2 to decompose to form 2cm3 of O2(g) 4. There was a big difference in rate of reaction when 4 and 5 discs were added respectively. Explanation of results The potato discs served as a source of Catalase enzyme. As the number of discs added to the hydrogen peroxide solution was increased, the concentration of the catalase enzyme also increased thus providing more activation sites to react with the substrate that was kept constant. This is evident as the time taken for amount of oxygen to be produced decreased as more potato discs were added. The big jump in reaction rates when 4 and 5 potato discs were added may have been due to little amounts f heat being given off which also further increased the reaction with its increased temperature. It can be predicted that by adding 6 potato discs the time taken to produce 2cm3 of would be less. Sources of error 1. Since knife was used in cutting up potato pieces, not all sizes were equal. The sizes of potato discs greatly affected the experiment since concentration of the enzyme catalase was directly proportional to the size and number of discs. This could be corrected by using more precise instruments to cut slices evenly to ensure fair results. Reference 1. A-level biology text book by Heinemann 2. www.biologyfactsof life.com 3. www.scool.com ...read more.

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