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The Effect of Substrate Concentration on the activity on the Enzyme, Catalase.

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The Effect of Substrate Concentration on the activity on the Enzyme, Catalase. Modifications When carrying out the experiment several activities stood out as needing improvements to produce valid results. Altogether four alterations have been made these are: 1. In the planning the stated method for increasing concentrations of hydrogen peroxide was to increase the molarity. However as different molarities of hydrogen peroxide were not available instead the concentration was increased adding more of hydrogen peroxide for each experiment. This method also increases the amount of substrate (hydrogen peroxide) molecules in the solution. Therefore has the same effect. The new concentrations used were: 2ml H2O2, 4ml H2O2, 6ml H2O2, 8ml H2O2 and 10ml H2O2. 2. Due to the lack of equipment to start the reaction the syringe contents (substrate) had to be pushed into the boiling tube and then the bung replaced. Rather than pushed through a hole with a bung in. This was a less precise option but unavoidable. 3. In practice a biurette was not used. The purpose of a biurette was to produce very accurate results. This is not necessary however because a measuring cylinder would suffice. A 10 ml measuring cylinder was used instead, which gave the results to 0.1 ml accuracy. This is accurate enough to plot a graph with. ...read more.


This type of reaction where a molecule is broken down into smaller components is called an anabolic reaction. On the first graph the reaction steadily increases until it reaches 6ml concentration and 6.1 of oxygen gas has been given off. Therefore as the concentration of hydrogen peroxide increases so does the rate of reaction. As more enzymes active sites are being occupied more oxygen gas is being produced. Until another factor such as enzyme concentration restricts the rate of reaction. This is because once all the enzymes active sites are occupied (said to be saturated) the enzymes cannot work any faster. The maximum numbers of active sites are being used. Therefore the time to enter and then leave the active site becomes a limiting factor. Any extra substrate molecules have to wait for an active site to be empty. Thus at the beginning of the graph we can see that the enzyme is in excess and therefore as more substrate is added the faster the reaction can go. When the graph levels off the substrate is in excess and therefore the enzyme is limiting. Therefore this experiment reflects the concentration theory. According to my results the fastest reaction was at 6 ml of hydrogen peroxide however the result might have been different had I used more concentrations for example every 0.5 ml intervals instead of 2ml intervals. ...read more.


Gas is lost before the bung is replaced. The results will be less than expected because gas will have been lost. A smaller amount of oxygen produced. 3) Impossible to start stopwatch and place hydrogen peroxide in the boiling tube simultaneously. Some experiments will have more time to react. It means that results are going to be slightly out from what they should be. If they have more time to react then the gas given off is going to be bigger than it should be. Therefore the results are not going to form the correct curve on the graph. 4) Large gas bubbles, which collect at the top of the measuring cylinder, cannot be included. E.g. These gas bubbles cannot be included in the table of measurements. Also if the tube is shaken then even more gas is released into the measuring cylinder (not a fair test). The results will be slightly less. Depending on how often this error occurs, this could alter the results slightly. 5) Pushing the bung into the boiling tube pushes air into the delivery tube. Extra gas can be incorporated into the experiment. Depending on how far in the bung is pushed some tubes will have extra air compared to others. The experiments will have more gas. However the measurements will be wrong. There will be a higher rate of reaction. 01/05/2007 Maryanne Parker 1 ...read more.

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