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Investigating and analyzing the factors affecting the rate of decomposition of hydrogen peroxide by catalyse in immobilised yeast.

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ABDULLAH QANDEEL INTRODUCTION In this experiment I will be investigating and analyzing the factors affecting the rate of decomposition of hydrogen peroxide by catalyse in immobilised yeast. This essentially an enzyme practical. You know that various things alter the rate of enzyme-controlled reactions. I plan to carry out an experiment that investigates how one factor alters the following reaction: Hydrogen peroxide (2H2O2) Catalyse Enzyme Water (2H2O) + Oxygen (O2) Enzymes are biological catalysts that speed up reactions in living organisms. Without them reactions would be too slow for organisms to survive. Hydrogen peroxide is a waste product formed in cells. Since it is a highly poisonous (a powerful oxidising agent), it must be broken down as quickly as possible. Catalyse is an enzyme found in all cells that breaks down hydrogen peroxide to water and oxygen (harmless products). It is a very fast enzyme (the fastest known today) As catalyse is found in yeast, a solution of active yeast provides a convenient source of the enzyme. I am going to first immobilise the yeast as it is much better to work with fixed quantities of the enzyme (catalyse) that does not get mixed up with reactants and products. The substrate reaches the enzyme by diffusion in the normal way, as the immobilising framework is porous. Enzymes such as catalyse are protein molecules, which are found in living cells. They are used to speed up specific reactions in the cells; these reactions are all very specific as each enzyme just performs one particular reaction. Catalyse is found in food such as potato and liver. It is able to speed up the decomposition of Hydrogen Peroxide because of the shape of the Hydrogen Peroxide molecule. This type of reaction where a molecule is broken down into smaller pieces is called an anabolic reaction. Enzymes are able to increase the rate of reaction without actually being consumed in the process. ...read more.


Time is a dependant variable and is a key aspect to the experiment. I use this system of starting the timing as soon as the bead touches the solution because it is much easier to identify and it also gives room for human error. I aim to drop the bead from a close hight so that the height dioes not take advantage in pushing the bead down further, therfore making the run take longer. I time using seconds and I use a normal stopwatch. Reliability I aim to repeat timings of each bead as many times as it takes to get satisfactory or adequate results. When I say satosfactory I mean results with 10% of each other. When I obtain three consistant results then I aim to move on to the next temperature. I understood this because I though about it during my perliminary work as a way to obtain accurate readings of this whole analysis. I will also keep an eye open if anything occurs which didn't occur during my perliminary experiment as there could be something wrong with the apparatus etc. It is extremly necessary to preform repeats. This is because it will help us to gain accurate understandings of the relationships between temperature. The relaiable a reading is the more powerful the results of an experiment is. That's why it is an important aspect to make your results reliable. I aim to ensure that my results are reliable by taking the following steps: * Obtaining clean apparatus * Calculating time accuratly by getting a reliable stopwatch * Concentrate on co-ordination of timing by starting time when bead touches water and stop when bead submerges. * Measure the ACTUAL temperature within water bath etc. * Record results(time in seconds) with two decimal places. Aparatus I aim to use specific pieces of apparatus. Apparatus will help me to be accurate and precise: * 10cm3 measuring cylinder * Hydrogen Peroxide * Sodium Alginate * yeast solution * 12 Bungs * 6 Water baths * ...read more.


It may be that in fact that many temperatures of solutions were lower than I stated.Overall, due to reliable repeats and in general predictions being confirmed I feel my results are reliable enough to make a conclusion.The obvious thing I would improve about the measurements I made would be to increase the range of temperatures used. Especially between 55�C-100�C. In this way it may be clearer at the temperature which denaturing took place, and would possibly give a graph that resembled the graph in background knowledge this would also give us a good spread.Also the experiment could be improved by bringing in results in to a closer percentage.Another way of improving this investigation is to change the method. The data that I collected was reasonable for the accuracy of my experiment, it was fairly reliable meaning that the results we collected were mostly expected but again with human error and contamination there were a few different results, which stood out quite a lot. But by adding the line of best fit everything came together and some basic conclusion were produced but also the results were just accurate enough to back up my prediction quite substantially.A major cause for concern on accuracy was the reading of the overall measurement of the oxygen produced as we measured it by using immobilised beads and observing them until they reached the top. There is substantial room for human and common error. I think the timing was as accurate and reliable as it could be, but only a second or third experiment would back that up fully. The equipment we used was reasonable but not the best, but for the conditions we were based in it was the best we were going to get, I think contamination was minor so that did not cause a problem. One problem with our preliminary experiments was that when we came to making the beads, the sodium alginate solution was contaminated with oher substances including yeast which could have affected my main experiment substantialy. Otherwise the general quality of all other substances used within the experiment was very adequate. ...read more.

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