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The Investigation of Catalase With Hydrogen Peroxide

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The Investigation of Catalase With Hydrogen Peroxide Introduction: Hydrogen Peroxide is a toxic chemical, produced by many living organisms as a product of the biochemical reactions occurring in the cells. As hydrogen peroxide is poisonous it must be removed quickly. The enzyme catalase speeds up the reaction that breaks down hydrogen peroxide into water and oxygen. Catalase H2O2 ------------------------> H2O + O2 Catalase can be found in potato cells. When hydrogen peroxide is added to the potato as a liquid, the catalase in the potato breaks down the hydrogen peroxide into water and oxygen - two substances which are essential for our bodies. Therefore catalase is essential in our bodies to break down H2O2. Aim: The aim is to think about what factors affect the rate of enzyme (catalase) reaction. My aim will be the investigation of the relationship between the enzyme concentration found in the potato and the rate of reaction of the enzyme catalase with the hydrogen peroxide. Hypothesis: Enzymes are proteins that are made in cells, which act as catalysts. A catalyst is a chemical substance that speeds up reactions without being used up itself so it can be used more than once. They speed up the rate of reaction by lowering the activation energy; the energy required to break the bonds of the substrate. Enzymes have a complex and specific shape and they catalyse reactions by forming a complex, called the enzyme substrate complex, at a specific region of the enzyme called the active site. Enzymes are specific; an individual enzyme can only catalyse one particular reaction. The induced fit hypothesis explains how enzymes work. When the substrate approaches the active site of the enzyme, the shape of the active site changes to fit precisely around the substrate; the substrate induces the active site to change shape. The reaction is catalysed and the products are formed. The products are a different shape from the substrate so they diffuse away from the active site. ...read more.


In this experiment I will be varying the concentration of catalase, i.e. the size of the potato. I will be start with 4cm of potato. I will then increase the concentration of potato catalase by cutting another 4cm potato in half so that there will be two 2cm pieces of potato. Then I will increase the enzyme catalase by cutting another 4cm piece of potato into 4 quarters so there will be four 1cm pieces of potato. I will increase the catalase concentration by cutting another 4cm potato into eight 0.5cm pieces. My maximum size of the potato will be 4cm; my minimum will be 0.5cm. To keep the test fair and reliable I need to keep the volume of hydrogen peroxide I use the same and the temperature it is at, which will be room temperature. I should keep the time of 10 minutes the same throughout the experiment. The potato should always be in contact with the liquid substrate to maintain a reliable result, so when I will be using a 4cm potato with 4ml of H2O2, I will need to keep the side arm test tube vertically straight so the liquid substrate is in contact with the whole potato. I will repeat the experiment for all the different concentrations at least twice, so that I mat be able to take a reliable average. Results: Experiment 1: Concentration of potato Volume of H2O at start (cm3) Volume of H2O at end (cm3) Total volume of O2 produced (cm3) 1x4cm 30.3 20.5 9.8 2x2cm 29.4 15 10.3 4x1cm 31.4 21 10.4 8x0.5cm 37.1 24.5 12.6 Experiment 2: Concentration of potato Volume of H2O at start (cm3) Volume of H2O at end (cm3) Total volume of O2 produced (cm3) 1x4cm 40.5 27.6 12.9 2x2cm 42 31.7 14.4 4x1cm 45.9 29.7 16.2 8x0.5cm 48.9 33.5 15.4 Averages: Concentration of potato Average O2 produced (cm3) 1x4cm 11.35 2x2cm 12.35 4x1cm 13.3 8x0.5cm 14 The plan managed to obtain some reliable results shown in the averages. ...read more.


The burette tap opening may have allowed small amounts of oxygen into the burette, making the results less accurate. Another major factor was the syringe with cork and pipette. This was probably the least accurate instrument used in the experiment. When the pull force on the piston was sucking in the H2O2 liquid, it was hard to keep the pulling force for the suction the same; so different amounts of H2O2 would have been drawn in even if it read that 4ml of H2O2 had been withdrawn. The pull force/suction was also affected by the tightness of the cork. Sometimes the cork was loose, so oxygen escaped, making the suction less powerful. Also, the pipette kept some of the liquid H2O2, and we did not measure how much H2O2 was inside the pipette. We assumed that all the liquid H2O2 was inside the syringe. The small variant amounts of H2O2 would have affected the experiment because it would have increased/decreased the amount of substrate molecules reacting and inducing with the active sites. Therefore the chances of inducing and reacting were more varied and the amount of oxygen produced and rate of reaction would also be affected. Another factor could be the inhibitors slowing down the reaction at different times. Generally I was quite pleased with my results and I think the procedure to obtain these results was suitable. I would however make a couple of changes to the experiment to make my results more reliable and easier to follow. Firstly I would change the way I recorded how much oxygen was produced. Rather than record ten minutes worth of oxygen produced, I could have recorded the time taken to produce a certain amount of oxygen. However I am still able to see how long it took for a certain amount of oxygen produced at a certain time as shown in my conclusion. To make my results more reliable I would have repeated the experiment at least one more time, but time was one of the factors that prevented me from doing this. ...read more.

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