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An Investigation into How Temperature Affects the activity of Protease Enzymes in Arial washing Powder

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An Investigation into How Temperature Affects the activity of Protease Enzymes in Arial washing Powder Introduction Proteins are complex biological molecules that are used for almost every function inside the human body, from keratin that forms the hair and nails to the proteins with which the experiment is concerned. This experiment will examine the effect of the protein-based enzymes that catalyse the breakdown of one molecule into another, in this case light-sensitive protein into amino acids. A protein is actually a string of amino acids that are joined together by peptide bonds between their amine and carboxyl groups in a condensation reaction, which produces a molecule of H2O, to form a polypeptide. This initial linkage between the multiple amino acids to form a chain is what is called the primary structure in the protein hierarchy. The next stage of the protein hierarchy is the formation of ? helixes or � pleated sheets as the functional 'R' groups attached to the amino acid. They begin to become attracted or repelled from the nearby R groups. After this comes the tertiary structure where the ? helixes and � pleated sheets begin to form bonds between each other. The bonds usually are ionic bonds, in which atoms with incomplete outer electron shells gain or lose electrons to form complete outer shells, hydrogen bonds, or disulphide bridges that form between two similar atoms (usually sulphur). It is these bonds that are affected by the action of a change in temperature. The tertiary structure provides the protein with a unique 3-dimensional structure. Finally the quaternary structure is where multiple tertiary structure level poly-peptides join together to form more complicated proteins. This is also the stage where inorganic molecules are attached to the proteins to form functionality within the molecule, such as with iron in haemoglobin. Enzymes are a variety of proteins that act as the body's catalysts. The job of a catalyst is to lower the initial energy requirement for a reaction to take place. ...read more.


I can tell this as the amount of the coloured light-sensitive protein from plastic film-strip that has been removed by the protease increases and thus the absorbency of the solution sample increases. Increasing the temperature in this range will increase the amount of kinetic energy in the solution. All the molecules will move faster and with greater force so that the collisions between active site and substrate not only happen more often but are more likely to result in a successful collision so the rate of the reaction increases. However, after this peak at 55OC the opposite happens, the rate of reaction begins to fall. This would be due to the protease enzyme denaturing and becoming unable to breakdown the light-sensitive protein. Excess heat can disrupt the bonds holding the tertiary structure of an enzyme together. Enzymes are globular proteins with a structure that is essential to their function. Even a slight change in the tertiary structure can alter the shape of the active site so that the substrate does not fit exactly into the active site because the structure of the active site is no longer exactly complimentary to the shape of the substrate. As the temperature increases, more and more active sites are changed so the overall rate of the reaction decreases. Within my results there were numerous errors shown by my error bars. There was overlap on 6 of the 11 possible overlap sites on my error bars. This is an obvious sign that my results are not very reliable. However the individual overlaps are notably small ranging from 0.01-0.02 absorbency units. However the largest overlap was of 0.03 absorbency units at 65OC. Due to the overall amount of over-lap an entire re-test of the experiment with revised procedures may be required, or at least a re-test of the results for 65OC. Aside from the small areas of over-lap on the individual error bars, the overall picture still shows an obvious trend of a rise in activity to 55OC. ...read more.


Second substances, of the three possibilities, I am most sure this one has not been the source of error. As I was only using factory-prepared strips of monochrome film and a batch of washing powder solution, there would be little chance of contamination as the film is individually stable and I kept the washing powder solution covered by cling-film to prevent any foreign bodies entering it. I also only used pure distilled water to wash out my apparatus and therefore that could not have been a source of error. Also, as I was using the same film and same batch of washing powder solution for all my experiments therefore all my results will be skewed by the same amount and therefore I will end up with no individual anomaly due to any error with the substances used. By process of elimination I am led to believe it is my measurement of my results that is the problem. As I was using only one measurement technique, the colorimeter, I am led to believe that somehow that is the problem. Upon investigation of the colorimeters manual I discovered a note that I had over-looked. "Allow 6-10 tests for the colorimeter to achieve optimum accuracy" (Colourwave CO7500 colorimeter manual). This piece of information is invaluable in explaining the first temperatures anomalous results. If the first six tests achieved are effectively written off due to the peculiarities of the instruments then my extraordinarily high results for the first temperature (30OC) are due to the instrument 'warming up'. I would have liked to have repeated the results at 30oC and allow the colorimeter to warm properly. I expect that this would show that my first set of results are all anomalies due to incorrect usage of the machine. Overall, I think that my original hypothesis that the optimum temperature of protease enzymes in Arial washing powder is between 50 and 60oC is likely to be correct but I cannot accept it on the results of this experiment because of the results obtained at 30oC. ?? ?? ?? ?? 1 18/10/2008 ...read more.

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