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For my coursework I will be performing an investigation into an experiment using hydrogen peroxide (2H2O2) as a substrate and Catalase as the enzyme, which will be produced by a potato.

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Science Coursework. Skill P - Planning my Investigation (8 marks) Aim For my coursework I will be performing an investigation into an experiment using hydrogen peroxide (2H2O2) as a substrate and Catalase as the enzyme, which will be produced by a potato. The enzyme Catalase is present in all aerobic tissues and catalyses the breakdown of hydrogen peroxide into water and oxygen. Hydrogen peroxide is a toxic by-product of many bio-chemical reactions within organisms, including aerobic respiration. The equation for this is: Catalase Hydrogen peroxide oxygen + water + Catalase (2H2O2) (2O2) (2H2O) This reaction can be discussed in terms of the activation energy and its effect on the rate of a chemical reaction. In order to get this reaction started, either some energy or a catalyst is required. Without it, the reaction would be much slower. In the case of my experiment, the Catalase will bind temporarily to the hydrogen peroxide particles they catalyse. In doing so, they lower the amount of activation energy needed and therefore speed up the reaction. Reactions can only happen when the hydrogen peroxide particles collide with Catalase molecules, but most collisions are not successful in forming product molecules. The 2H2O2 molecules must collide with enough energy to break the original bonds so those new bonds in the product molecules can be formed. All the rate-controlling factors are to do with the frequency of reactant particle collision. In the case of temperature, the energy of the collision is even more important than the frequency effect. I need to change ONE factor in my experiment to measure the rate of reaction between the 2H2O2 and Catalase, and to see if a change in the chosen factor will affect the rate of the reaction in any way. Here is a list of the factors I can change and their effects on the experiment: Surface area of the Potato: If a solid reactant or in this case a solid catalyst (Catalase in Potato) ...read more.


I also washed and dried all the equipment between each section of the experiment. 4. To ensure my results were as accurate as possible I used a digital stopwatch, graduated measuring cylinders and measuring tube. The Catalase enzyme in a potato was used for this investigation. I kept the following variables the same: * 5 pieces of potato * Each weighing 3.4gms * Volume of the 2H2O2 was 20ml * Concentration of 2H2O2 was 20V * Ph of the 2H2O2 was 8 (alkaline) * Volume of water in the measuring cylinder will be 100.0ml * Room temperature is 25�C approximately 5. When all the apparatus was set up, and I had started the experiment, I started of by using a knife to cut my potato into 1-inch thick strips. The strips were placed on a ceramic tile and a knife was used to cut them into 3cm in length. 6. The weight and lengths of the strips were measured as accurately as possible by placing the strips against a ruler with millimetre units marked on, and then weighed on the electronic scales. 7. A tub was filled half way with water, and a plastic measuring cylinder was also filled with water and placed up side down into the tub to hold the water inside. The stand, clamp and boss were used to hold the cylinder in place, and the bung was removed from the flask. The rubber delivery tube was placed inside the measuring cylinder, and the other end was fitted into the bung with a hole, free to collect the oxygen being produced in the flask. 8. A small measuring tube was used to place 20cm� of hydrogen peroxide solution at pH 8 into the glass flask. This was then put into a water bath, to increase the temperature to 27�C. 9. Care was taken to count 5 potato pieces and add them to the flask. ...read more.


To overcome this problem I could keep the flask containing the hydrogen peroxide in a hot water bath for all the temperatures making sure that the water bath was the suitable depth. This would ensure constant temperature throughout the whole experiment. Looking back at my results I found some anomalous results in my findings. When averaging I used these results, which could of made the average either lower or higher than it should be. To improve this I should have missed these results. Not including some sets of results when making averages may have led to better values. My results are in line with those I predicted. Graphs indicate rise in temperature up a point leads to an increase in oxygen production. This is in line with kinetic theory. However it is very clear that after a certain temperature is reached the enzyme actually virtually stops. This supports my theory of lock and key fit. However optimum activity of enzyme is at about 37�C this is as we expected. But at 50�C the enzyme is still not denatured according to my results. This is a higher temperature than I would expect. Possible not allowing solutions to reach temperatures selected has led to an inaccuracy. It may be that in fact that many temperatures of solutions were lower than we 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, maybe have gone up to about 60�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. Another way of improving this investigation is to change the method. I measured the time taken to produce 30cm� of oxygen, when I could have measured volume of oxygen that was produced. ...read more.

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