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Investigation on how pH affects free and immobilised catalase enzymes.

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Investigation on how pH affects free and immobilised catalase enzymes Aim My aim in this experiment is to find out whether the reaction rate of particular enzymes more affected by pH 4.4, 5.2, 6.5, 7.0, or 7.5 more when it is immobilised by using sodium alginate to trap it in beads or just used as free enzymes. And from this I can compare whether the reaction rate differs most in free or immobilised. Research Catalase occurs in many plant and animal tissue. It breaks down toxic Hydrogen peroxide, formed as a by-product of various biochemical reactions, into water and oxygen. The activity of most enzymes is influenced by changes in pH. In this experiment, potato discs in solutions of known pH act on hydrogen peroxide, and the rate at which oxygen is evolved is measured. This reflects the activity of the Catalase in the potato. Each enzyme has an optimal Ph, which is the Ph that it works the fastest and breaks the most substrates down in the least time. Most enzymes work best at a Ph of about seven which is near neutral and our bloods natural Ph. They work the best at this temperature as they are proteins themselves and proteins can also become denatured by too acidic or alkaline conditions as well as high temperatures. Catalase the enzyme that I am using is a very important enzyme because it is present in every single cell in living organism. It works inside the cells of both animal and plants cells like in the liver for animals and potato cell for plants. It breaks down hydrogen peroxide in the cells that it is present in; this makes it important, as hydrogen peroxide is a very poisonous substance produced by a lot of the chemical reactions in the body. Catalase ids found in large doses in the liver and the kidney which helps filter out waste products from the blood this makes it a suitable place to have a lot of catalase. ...read more.


Take care of other glassware, keeping them away from the edge of the workbench to avoid any breakages that may cause injury, especially the boiling tubes as they can roll around. Potato: It is of low risk, but should be kept in a clearly labelled container. Products of reaction: The product is water so there is a low risk. However, as the pH of the buffers present in the mixture of the reaction, in some experiments, have slight hazards, avoid contact with the skin. To dispose of the residue, decant off any liquid present, washing it away down the sink and use a spatula to remove the potato out of the boiling tube to be discarded. Control Since in this experiment I am varying the pH of the solutions, the state in which the enzyme catalase is in whether it be free or immobilised I will need to keep a constant by which I may be able to accurately and surely record my results. The constant that I shall be keeping the same in my experiment thought by which I may measure everything by shall be the mass of the potato which shall be at a constant 10grams plus or minus 0.10g. Method Before I started my experiments I made two stock solutions of 250cm3 one with5.25g of citric acid (A) and the other with 7g of anhydrous disodium phosphate (B). To make ph 4.4 mix 27.9cm3 A with 22.1cm3 B, ph5.2 23.2cm3 A 26.8cm3 B, ph 6.5 14.5cm3 A 35.5cm3 B, and ph 7.5 using 3.9cm3 A 46.1cm3 B. I then created my sodium alginate solution by mixing 2 grams of sodium alginate with 100cm3 of distilled water; I then mixed it and heated it for about 10 min to quicken the settling of the solution. To obtain the enzyme catalase I bought some potatoes roughly weighing 500 grams each. I then skinned them, chopped them up and liquefied them in a blender. ...read more.


I would also use an electronic scale, which had a greater degree of accuracy in terms of decimal places. This is due to the fact the scale only went up to 2 decimal places and even then I weighed the mass of potatoes to plus or minus o.10 grams and next time would use a more accurate scale and try to be more accurate in weighing the potatoes myself. Also if I were to redo this experiment I would dry the potato so it would provide more accurate results, as the water would not be weighed but jut the dry mass of the potato. I would also use a pH meter to test the acidity or alkalinity of the pH to make sure I had exactly a pH of 4.4 or 5.3 as I might have measured out the wrong volume of each buffer. This brings to me another point which concerns the actual volume of solutions A and B that I used, to make my results more reliable I would either use a smaller scale measuring cylinder to measure the volume. Or I could work out how much one mole of solution A and B weighs in grams and then from that I can weigh the solution on a scale to see what mass of each solution should be used. Another part of my experiment that I could improve was the actual size of my beads as I feel that I should have made them all the same size as I only made them by squeezing the alginate the solution through a syringe. So next time I would use the proper apparatus that would make beads of exactly the same size, concentration of catalase and hopefully the same mass. When collecting my oxygen the pipes I used to transfer the oxygen to the unturned grated cylinder were not insulated with Vaseline to produce an air tight passage which could have resulted in losses of oxygen and rendered my results anomalous and useless but which when looking at the results table doesn't seem to have occurred. ...read more.

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