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effect of enzymes on a reaction

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What is the effect of Enzymes on a reaction? Introduction There are many factors which affect the rate of reaction; temperature, substrate concentration, enzyme concentration, ph and inhibitors. Catalase is a very fast acting and efficient enzyme, therefore making it ideal for my experiment. Catalase catalyses the decomposition of hydrogen peroxide (H2O2), into water (H2O) and oxygen (O2). One molecule of catalase can convert millions of molecules of hydrogen peroxide to water and oxygen per second. 2H2O2 2H2O + O2 Enzymes are catalysts and like all catalysts, enzymes work by lowering the activation energy, thus dramatically increasing the rate of reaction. Enzymes are not consumed by the reactions they catalyse, neither do they alter the equilibrium of these reactions. The enzyme catalase is found in microbodies or peroxisomes in eukaryotic cells. A main source for catalase is the potato tuber. Enzymes are very specific, and it was suggested by Emil Fischer in 1894, that this was because both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another. This is often referred to as "the lock and key" model. However, while this model explains enzyme specificity, it fails to explain the stabilisation of the transition state that enzymes achieve. ...read more.


If the amount of substrate molecules in the solution exceeds the number of active sites available then the rate of reaction will no longer go up. This is because the maximum number of reactions are being done at once so any extra substrate molecules have to wait until some of the active sites become available. The least amount of oxygen will be given off by the 10vol solution this will be because there is not enough substrate to fill the active sites of the enzymes. It works in a similar way as if there were not enough enzymes and therefore active sites for the substrate to fill. Equipment Apparatus Number/Volume required Purpose Reason for choice Potato x1 To catalyse the It contains Catalase which is hydrogen peroxide needed for the reaction. Hydrogen peroxide 45cm3 To decompose It has a very fast rate of reaction, it is suitable for my experiment. Distilled water 15cm3 To dilute the It is purer than tap water, has hydrogen peroxide fewer impurities which will improve accuracy. Ruler x1 To measure lengths It makes it easier to measure the of potato lengths of the potato. Tile x1 To cut potato on It protects the table whilst using a scalpel. ...read more.


The displacement method is also not entirely as accurate as using a gas syringe to collect the gas given off. On a gas syringe it is easy to get a direct reading, whereas, in my experiment I had to use measuring cylinders which were actually too big, as my reaction did not give off a large amount of gas, so it was hard to get a correct reading. I did use only one potato to get my results from which made my experiment a fairer test, however as I had to do my experiment over 3 days with limited time periods in which to do my experiment, I kept my potato in a beaker with distilled water just covering them to keep them fresh. They may have absorbed a little water in this process but my results in my repeats were all similar so I assume that this did not affect my results too much. Also, although only slowly, hydrogen peroxide still decays in the absence of a catalyst, this too could affect the results. It would also have been a more of a fair experiment if I had left all of my equipment set up and used the same equipment every time. In general for a lot of factors, it would have been better if the experiment had taken place all on the same day. ...read more.

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