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What influence does pH have on the enzyme Catalase?

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Biology Data Analysis What influence does pH have on the enzyme Catalase? _____________________________________________________________________________ Enzymes act as catalysts in the cells of an organism, speeding up a chemical reaction but remaining unchanged itself. Most enzymes break down large molecules into small molecules. However, others can join small molecules together. Enzymes are important in an organism because they regulate the many chemical reactions that take place inside the cells in the process of metabolism. They are proteins, made of long chains of amino acids folded into a complex shape called a globular protein. The molecules in the reaction, called the substrate, must fit exactly into the enzyme in a place called the active site, which is where the reaction takes place, for the enzyme to work. Changes in the environment the enzyme, for example temperature or pH, can affect the active site shape and therefore they change the rate of reaction. This data analysis was to investigate the influence of pH on the rate of reaction of the enzyme catalase in potatoes. Catalase breaks down the highly oxidising hydrogen peroxide, into water and oxygen. 2H2O CATALASE 2H2O + O2 Hydrogen peroxide is formed as a by-product of various other biochemical reactions and would damage cell membranes very quickly if not removed, so catalase is an essential enzyme to work quickly and effectively. Catalase occurs in many plant and animal tissues, but this experiment used the catalase in potatoes. During the experiment, potato discs which naturally contain catalase were placed in a solution of a known pH and hydrogen peroxide. Then the rate at which oxygen produced evolved the manometer liquid within twenty seconds was measured. The oxygen production proved that there was a reaction taking place and the movement reflected the rate of reaction of the catalase in the potato, measured in mm/20s. The class used eight different potatoes at a range of pH values from pH 4 to pH 8. ...read more.


When the pH became so acidic and the whole enzyme's ionic bonds began to be changed and the enzyme active site denature the graph fell steeply as shown between pH 5 and 4. When all the enzymes were completely denatured there would be no reaction at all. Evaluation Evaluation of procedures The experiment had a simple method, which was easy to repeat in the same way again. It was also very safe to conduct, if you followed the explicit safety precautions wearing safety goggles and lab coats and being highly careful with the highly oxidising hydrogen peroxide and dangerous apparatus such as knives or broken glass if a test or manometer tube was broken. It was completed in a reasonable amount of time and it gave a wide set of data that could be studied and analysed. However, it the data was not as reliable as it could be. The range of rate of reaction for each pH was huge. For example at pH 8 the results ranged from 37 to 134 mm/20s. This meant that there was a large degree of overlap between the error bars representing the range of values, and even the boxes in Figure 2 showing the majority of the data in the inter quartile range, at the different pH. This means we cannot be certain in the conclusion as the true value could fall anywhere in the range. It shows that the data collected was not particularly accurate. The fact that the results were not completely accurate could be due to the method as there were several experimental flaws in the investigation and there are a number of improvements that could be made to improve them and therefore get a more accurate set of data to make a reliable conclusion from. These were the main problems and a suggested improvement: 1. Issues with the apparatus/techniques Measuring the rate of reaction by seeing how far the oxygen produced evolved the manometer fluid was an inaccurate method. ...read more.


Therefore, I cannot be certain even if the scientific theory and some of the data show it. There are weaknesses in the techniques, as discussed in the 'Evaluation of Procedures', which would have affected the accuracy of the data, which limits the faith I can place in the conclusion. This included the lack of precision of some of the apparatus, such as the oxygen escaping from the tube you had to hold down and, also the lack of control of variables. The range was not adequate to see the full effect of the whole spectrum of pH, both acid and alkaline. This is why although I am only reasonably confident I cannot place full confidence in the conclusion. However, we could have more confidence if we amended these problems by: * Using the improvements in apparatus and techniques described in the 'Evaluation of Procedures' to make the data more accurate and therefore more reliable. * Extending the range to use more alkaline pH values, such as pH 9, 10, 11, 12 to provide more evidence for the second aspect of the conclusion. It would also help to continue testing more acidic pH values to see when the enzyme was denatured to such an extent that it could not react at all with the hydrogen peroxide. This would display the full effect of pH on catalase for us to base the best conclusion on. * Including pH values at smaller intervals to ascertain the optimum pH more accurately. * Taking further data at each pH 6, where there was a lack of it, as to get a better picture of what the effect of this pH is These ideas would make the data be more accurate and complete, and therefore make the conclusion more reliable and secure. 1 Source: 'Twenty First Century Science GCSE Biology' published by OCR (page 101) 2 Source: 'Twenty First Century Science GCSE Biology' published by OCR (page 101) 3 Source: Chemistry Help Website: http://www.chemguide.co.uk/organicprops/aminoacids/enzymes2.html ?? ?? ?? ?? Anna Broadley BIOLOGY DATA ANALYSIS UVC - 1 - ...read more.

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