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The activity of Enzyme Concentration on Hydrogen Peroxide.

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The activity of Enzyme Concentration on Hydrogen Peroxide. Introduction In this investigation, I will be investigating the activity of the enzyme Catalase on the substrate hydrogen peroxide (H2O2). Scientific Background Enzymes are biological catalysts that speed up the thousands of metabolic reactions that occur in living cells. They are usually large proteins made up of hundreds of amino acids, and often contain a non-proteinaceous group, known as the prosthetic group. This is what is important in the actual catalysis. In an enzyme-catalyzed reaction, the substance to be acted upon, the substrate, binds to the active site of the enzyme. The substrate is held to the enzyme in an enzyme-substrate complex by hydrophobic bonds, hydrogen bonds, and ionic bonds. The enzyme then converts the substrate to the reaction products in a process requiring several steps, and often involves covalent bonds. Finally, the products are released. By allowing this to occur, the enzyme reduces the activation energy required in any chemical reaction. All chemical reactions require energy for them to occur, because there is an energetic barrier that reactants must overcome for them to be converted into the products. Once enough energy is supplied, a position called the transition state takes place, and the reactants can then form the products. This energy is called the activation energy. Enzymes reduce this activation barrier. Each enzyme is specific for a certain reaction due to its unique amino acid sequence, which causes it to have a unique three-dimensional structure. The active site also has a specific shape, therefore only allowing few of the many compounds present to interact with it. ...read more.


The measuring cylinder is then emptied into the delivery funnel, giving a more accurate amount of substrate used. The tap will have been closed so that no H2O2 will have dripped into the potato discs. * The tap is opened and, simultaneously the clock is started. When all the H2O2 is emptied the tap will be closed, to stop any gas from escaping. The gas then flows through to the gas syringe, which will take the reading of gas evolved. Measurements of the gas evolved are taken, especially at the start to give a more accurate interpretation of the initial reaction, as at that point the substrate in excess, so this gives the most accurate estimation of what the rate of the decomposition is, when the enzyme is involved. * Readings are taken at 5secs, 10s, 15s, 20s, 30s, 40s, 50s, and 60s. * Once the results have been noted the conical flask is removed, and washed using water. Though the enzymes are reusable, new discs of potato are used in their place. This time, maybe a differing amount of discs is used, giving a more varied enzyme concentration. * This method is repeated for until all results are recorded. For each concentration of enzyme, 3 different readings are taken and an average of the results is taken, if they are consistent. Safety Precautions The following safety precautions will be maintained throughout the experiment to maintain a safe working environment. o H2O2 is corrosive, and at 20% is definitely an irritant. o Goggles, lab coat and gloves must be worn at all times. o Care must be taken when using sharp implements. ...read more.


This is why discs are going to be used because they each have the equal amount of exposure of any cylinder, no matter what length. * The measuring cylinder on a beehive was just impractical. It was not stable and the displacement was hard to read off accurately. An alternative was to use a gas syringe. This will be used in the experiment because of the practicality. Results: The following results were obtained: Volume of O2 produced/ml Length of potato/cm 10 seconds 20 seconds 40 seconds 3 3 5 8 5 4 6 6 7 7 8 9 Conclusion From the results table it can be seen that the initial rates do increase with the increase in length. However, eventually all of the cylinders gave off between 8-9ml at the end. Though the amount of O2 being produced increases there should be a decreasing rate. However, this cannot be seen from the graph above for "3cm". This may be due to the cylinder's lack of exposure to the H2O2, and a substantial result could not have been achieved. The 5cm cylinder does show the predicted trend of an increasing rate, then a constant rate. This gives further support for the prediction. The 7cm also portrays the predicted trend. Though it hasn't reached its constant rate, the rate is slowing down. The graph also supports the prediction made that because there is the same exposure of enzymes, no matter what length of cylinder. This is because there is not vast difference between the results. With an exposed surface maybe more dramatic and substantial results will be achieved. Overall the preliminary investigation was an effective way of supporting predictions made and also trying and improving the method. ...read more.

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