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To examine the effect of temperature on the enzyme catalase.

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Introduction

Biology coursework AIM To examine the effect of temperature on the enzyme catalase. INTRODUCTION * What are enzymes At the most basic level, enzymes are biological catalysts. They are proteins, meaning that they are polymers of amino acids. Their tertiary structure gives them a globular form due to the bonding present in the molecule. Many types of bonds hold the structure together and in the right shape. They strongest of these are the di-sulphide bridges between two cysteine amino acids. Also present are hydrogen bonds, although singly week when many are present the bond is strong. In addition are hydrophobic non-polar R-groups which by pointing to the middle of the molecule act as a bonding force. Every enzyme is present to speed up a reaction or make the reaction workable in 'normal' circumstances. However enzymes are not universal. So how does the simple molecule decide what reaction it will aid? Each enzyme has an active site. This site is designed specifically to allow the substrate to cling to the enzyme forming an enzyme-substrate complex. However it does occur that other molecules fit into the active site. This is known as either competitive or non competitive inhibition * What is Catalase specifically Catalase is an enzyme found in most creatures. It converts naturally produced hydrogen peroxide into water and oxygen. The equation for the reaction is: H2O2 H2 + O2. "Catalase is an example of a particularly efficient enzyme. Catalase has one of the highest turnover numbers for all known enzymes (40,000,000 molecules/second). This high rate shows an importance for the enzymes capability for detoxifying hydrogen peroxide and preventing the formation of carbon dioxide bubbles in the blood." i (Unknown author) * Denaturing and Ideal Conditions Like all proteins and enzymes, Catalase is not impervious to heat. At a certain temperature the bonds that hold the shape together will break and so the active site will change shape causing the enzyme to lose function. ...read more.

Middle

However the area in these is very large and the scale is large. The laboratory had only one glass gas syringe. If this should have become broken or damaged there would not have been a replacement. Plastic gas syringes are not as accurate. This is because they are prone to sticking, when this happens, the pressure can build and the rubber tube can come off. This would result in a large loss of gas. Before the reaction took place it was made sure that the burette was perpendicular to the ground (this ensured accurate reading of the meniscus in the burette) and that it was full of water. Also the delivery tube was placed inside the burette but below the first line on the burette. The reactants were then placed in separate boiling tubes and they and a third empty boiling tube were placed in the water bath to get them to the desired temperature. After five minutes at that temperature, first the potato was put into the third boiling tube and then as the H2O2 was poured in the bung was put in and the timer started. The boiling tube was then shaken vigorously for the two minute duration of the experiment. As the hydrogen peroxide decomposes, froth builds up on the top. However this could not be stopped; also produced is O2 bubbles. These rose to the top and went through the delivery tube into the top of the burette. This displaced the water. Every thirty seconds the number closest to the bottom of the meniscus of the water in the burette was recorded. APPARATUS & MATERIALS Water bath; burette; Bunsen burner & mat; retort stand & boss; boiling tube x 3; mercury thermometer; delivery tube & bung; 20ml measuring cylinder. 9:20 diluted potato solution; 50 vol H2O2; ice. RISK ASSESSMENT Potential Hazard Precautions Enzymes are potential irritants and allergens The enzyme will only be handled in solution and will be diluted. ...read more.

Conclusion

There were no significant anomalous results. This can be seen in the graph as all the points fall on the lines. As can be seen on the graphs, for almost all the points the limit lines are very small. However, in the higher temperatures the 30 second points have larger limit lines. These could be diminished by more closely controlled data collecting When a test was done with manganese dioxide, no results were taken because MnO2, being a chemical catalyst, made the reaction finish within seconds. As the data was being taken every 30 seconds, this was useless. Although there were some errors in the results, for instance the last point on the 0�C line, because natural ingredients were used, this was to be expected. This was also the reason why the two sets of results are often further that 1cm3 different yet not classed as erroneous. The apparatus (shown in appendix A) was sufficient for this practical.. In this practical pure Catalase was not used but a potato solution had to be used. This potentially caused complications that polluted the results. This is probably the cause of the inaccuracies in the results. If the Catalase could be isolated then the results may be very different. It would be interesting to compare the results from that reaction and the reaction carried out here. From that one could see how other molecules interact with this process and to what end. I think that despite a few problems with the materials the conclusion is a safe one to make with the data available. An additional piece of apparatus could be added to supplement and enrich the data. If the experiment were done in a conical flask on a mass balance, the weight loss could be included in the data. Although there were a few areas of inaccuracy the data are still valid. With the extra measures and checks and more time to collate more data the results would be much improved 1 For step-by-step instructions see appendix i http://www.seps.org/oracle/oracle.archive/Life_Science.Biochem/2001.07/000994160576.9934.html ii http://www.blc.arizona.edu/marty/181/181Lectures/Figures/POHS_Figures/Chap6/Fig6_13.gif ?? ?? ?? ?? Richard Rees Page 1 Biology AS coursework ...read more.

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