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An investigation into the effect of substrate concentration on the activity of the enzyme 'Catalase` in potato tissue.

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A/S level Biology Coursework An investigation into the effect of substrate concentration on the activity of the enzyme 'Catalase` in potato tissue Plan Aim The aim of this experiment is to examine how the concentration of the substrate 'Hydrogen Peroxide' affects the rate of reaction of the enzyme 'Catalase'. Background information Enzymes are biological catalysts made up of proteins. Enzymes such as 'catalase' are the protein molecules, which are found in living cells. The use of these molecules is to speed up specific reactions within the cells, however becomes denatured at temperatures above 45�C. Enzymes are highly specific molecules, as each has its own particular reaction to carry out. The catalase enzyme can be found in many foods, including potatoes and liver. The catalase enzyme's particular reaction purpose is to remove Hydrogen Peroxide from cells. Hydrogen Peroxide (H2O2) is the poisonous by-product of metabolism. It is a colourless, syrupy liquid that is a strong oxidising agent and in cold-water solution, is a weak acid. It is miscible with cold water and is soluble in alcohol and ether. Being a normally fairy stable compound, Hydrogen Peroxide decomposes into water and oxygen when heated above 80 C, as well as in the presence of some catalysts such as catalase. ...read more.


Both substances were taken from the same source each time. Safety The chemical 'Hydrogen Peroxide' is highly corrosive. Care must be taken to prevent injury at all times and chemicals must be controlled to an appropriate manor. To protect from contact with skin or eyes, protective goggles and gloves will be worn, as there is a possibility that hands may come into contact with the substance. Also a lab coat to protect from spillages is necessary. Implementing Results were obtained as accurately as possible. After each use, the equipment was washed. Upon beginning the experiments, it became clear that certain aspects of the original plan needed to be improved. Limited availability of equipment and the original measurements within the plan needed to be attended to. Modifications made Before the experimental period took place, a lack of equipment meant that a syringe could not be used to measure gas, and so a delivery tube fixed with a bung would be used. This gas would then travel into a boiling tube placed in a water trough as the diagram below shows; The first problem encountered in the initial stages of the experiment was that the 4cm� only covered roughly 25% of the potato core. ...read more.


This evidence is sufficient for a confident statement that 'as the concentration of substrate increases, as does the amount on oxygen produced'. The rate of reaction also needs to be calculated to show the way in which the rate of reaction is affected. This will be worked out from the mean of each concentration of Hydrogen Peroxide. The equation for this calculation is below: Rate of reaction = Amount of gas produced Time The calculations for the means were as follows: 20% concentration of Hydrogen Peroxide = (10cm�/126(secs)) = 0.079cm�/sec 16% concentration of Hydrogen Peroxide = 0.075 12% concentration of Hydrogen Peroxide = 0.063 8% concentration of Hydrogen Peroxide = 0.053 4% concentration of Hydrogen Peroxide = 0.036 0% concentration of Hydrogen Peroxide = 0 With the above calculation results, it can be proved that as the concentration increases, so does the Rate of reaction. The graph also shows that... Working out the standard deviation between the results achieved would also be useful. This will also be plotted on my graph. The formula for working out the standard deviation is: ? ? ??� - (??� n This equation is used to work out the standard deviation for the substrate in the following way. The following example demonstrates how the standard deviation is calculated for 20% concentration. Using the above equation, we can replace symbols with figures. ...read more.

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