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Observing the Rate of Reaction of the enzyme Catalase upon changing Concentrations

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Valentina Zunarelli IB Biology Practicals Observing the Rate of Reaction of the enzyme Catalase upon changing Concentrations Aim To identify at which concentrations of salt solution (0%, 0.5%, 1%, 1.5%) the enzyme catalase (liver) works best and breaks down the most hydrogen peroxide. Introduction Enzymes are proteins that act as catalysts. They are made in cells. A catalyst is something that speeds up a reaction, but does not get used up in the reaction. One can usually be used many times. The majority of the reactions that occur in living organisms are enzyme-controlled. Without them, the rate of the reactions would be so slow as to cause serious, if not fatal, damage. Without enzymes toxins would soon build up and the supply of respiratory substrate would decrease. Enzymes, being proteins, have a specific shape. They are therefore specific in the reactions that they catalyse - one enzyme will react with molecules of one substrate. The site of the reaction occurs in an area on the surface of the protein called the active site. Since the active site for all molecules of one enzyme will be made up of the same arrangement of amino acids, it has a highly specific shape. ...read more.


Using the graduated cylinder, put 10ml of H2O2, into the baseline 1. Using a pipette add exactly 1ml of water into the same beaker. Add 10 ml of sulphuric acid and mix well. Extract a 5ml sample from the beaker labelled baseline 1, and put it into the beaker labelled baseline 2. Then, using the burette, add a drop of potassium permanganate at a time into the beaker until a persistent brown colour is obtained. Swirl the solution after each drop is added. Record how much potassium permanganate was used to obtain the brown colour, this is called the baseline reading. 2. Now, Take five of the twenty two beakers and label them 10s, 30s, 60s, 120s, and 180s. Arrange them into a line, from lowest to highest. Put 2ml of the 1.5% H2O2 solution into each beaker, and using the pipette add 2ml of water into each one as well. Also add the catalase, which is a small cube of 0.5cm2 of liver, into each of the five beakers. This has to be dropped in at the same time for each beaker and the stop watch should be started. ...read more.


The amount of pottassium permanganate used is equal to the amount hydrogen peroxide that remainsafter it has been broken down by the catalase (liver). When the pottassium permanganate has turned the solution brown, this eant that it had neutralised the hydrogen peroxide and therefore their volumes were equal. The concentration of salt solution where the most hydriogen peroxide has been brocken down is the 1.5% solution. This was the optimum concentration for breaking down hydrogen peroxide The enxyme in this experiment was the catalase (liver), the substrate was the hydrogen peroxide and the products wer water and oxygen as predicted. Evaluation On the graph, it is clear that there are a few anomalies since as time increases each point should be lower showing a smaller amount of hydrogen peroxide present since more of it is able to break down in more time. Tese mistakes could have been eliminated by doing the experiment at least three other times, although this would have taken a long time. Also, the addition of sulfuric acid may have altered the test since this is an extra volume of acid present to be neutralised. However, stopping the reaction is essential so it is a remaining problem. ...read more.

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