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Investigation on how pH affects free and immobilised catalase enzymes.

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Introduction

Investigation on how pH affects free and immobilised catalase enzymes Hypothesis I hypothesis that as the ph of the solution that my enzymes are in (immobilised or free) moves away from neutral to more acidic or alkaline solutions that the amount of oxygen produced from the break down of hydrogen peroxide decreases. This can be explained by the research in which I stated how in acidic conditions enzymes are H+ acceptors and H+ donators in alkaline solutions this then breaks and destabilizes the ionic bonds denaturing the enzyme as it becomes unravelled. Also in my research I stated how the H+ ions would alter the globular shape of the protein distorting the active site. This distortion would affect the reaction rate as it would slow down due to the active site being distorted so it takes longer to break down the hydrogen peroxide and because more and more of the enzymes become distorted by the excess H+ or OH- ions meaning less active sites that are available to carry out the reaction. This can be proved by my preliminary test results, in which is showed when the ph was 13 or 2 the amount of oxygen produced was significantly reduced. I finally hypothesis that the immobilised enzymes have a higher tolerance to ph this is due also to my research which showed that when immobilised enzymes were more tolerant to heat and so I can theorise that it may also be the same for changes in ph. This can come about by saying the beads in which the enzymes are in are protecting the enzymes. More concrete evidence for my hypothesis about how ph has less of an affect on immobilised enzymes are my preliminary test results on that show compared to the free enzymes they actually produce more oxygen, hence ph changes affect them less. Introduction 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. ...read more.

Middle

I shall also be controlling the hydrogen peroxide solution to a 10-vol solution of 5cm3. The temperature shall also be kept constant at a temperature of 40 degrees, as this is roughly the optimum temp for the enzymes to break down the hydrogen peroxide. This is due to the enzymes being mesophiles (optimum temp of reaction below 40 degrees). To control the temp I shall be using an electronically maintained water bath, and a thermometer to check the set temp. I shall also be controlling the bead size as this may slightly affect the rates of reaction so the same size nozzle shall be used, this will be cleaned regularly Incas of clogging which may upset the bead size and create possible anomalies. Finally rigorous measuring at stages so as not to upset the ph balance thus affecting the results of the experiment will control the ph solutions. 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). I then created different ph solutions; the table below will explain in detail how to create the different ph solutions. Ph solution Solution A Solution B 4.4 27.9cm3 22.1cm3 5.2 23.2cm3 26.8cm3 6.5 14.5cm3 35.5cm3 7.0 Distilled water Distilled water 7.5 3.9cm3 46.1cm3 The above table shows the ratio to which I mixed the solutions A and B to make the variable ph contents. 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. I measured out roughly 10 grams of liquefied potatoe plus or minus 0.10grams, as that was the greatest degree of accuracy that the scales I was using could offer. I measured out 10 grams about 30 times as I would need 10g 5 times for each experiment with different pH, I would be doing 3 experiments for immobilised and free enzymes. ...read more.

Conclusion

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. Whether or not I did this precise experimental procedure again, if I were to do one which included the use or an alginate solution n I would use a magnetic mixer as it would mix the solution quicker, make it smoother and save me stirring the solution with difficulty in whilst it resides in a water bath, which could be potentially dangerous. ...read more.

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