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the Effect of Copper Ions on a

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Introduction Aim Copper ions are heavy metals therefore copper sulphate (CuSO4) is likely to be an inhibitor. This is since heavy metals are known to be inhibitors having an effect on enzyme functioning. In this experiment I will investigate how a range of copper sulphate concentrations affects the ability of the enzyme amylase to hydrolyse starch into maltose. Hypothesis I predict that as I increase the concentration of CuSO4 the more time it will take for the enzyme amylase to hydrolyse starch into maltose thus the rate of reaction will decrease. This is since the Cu2+ is likely to alter the shape of the active site of amylase hence reducing the enzyme's ability to catalyse the reaction. I know that as I double the concentration of CuSO4 twice the volume of copper ions will be present for the same given volume. This therefore means that the chance of the copper ions colliding with amylase will increase by a scale factor of 2. The chance of a collision is random but doubling the concentration of CuSO4 means that the average chance of meeting copper ions will increase by a scale factor 2. Thus I quantitatively predict that as the concentration of CuSO4 doubles then the time for my reaction to take place will also double. Thus the concentration of CuSO4 will be proportional to the time of the reaction (see graph A) hence the rate of reaction will be inversely proportional the CuSO4 concentration (see graph B). Predicted Graph A CuSO4 Concentration (mol dm-3) Predicted Graph B Scientific Background Amylase is a digestive enzyme which speeds up the rate of a reaction by reducing the activation energy required for the enzyme to hydrolyse starch into maltose, however at the end of the reaction the enzyme remains chemically unchanged. The enzyme hydrolyses the polysaccharide starch by breaking the glycosidic bonds converting it into the disaccharide maltose. ...read more.


The volumes of distilled water and of CuSO4 (0.1M) used to make up the different concentrations of copper sulphate are very small as shown in the table on the previous page. Thus in order to increase the accuracy of the copper sulphate concentrations, a 1cm3 syringe will be used. My actual experiment method will be improved in many ways. * A water bath will be set up at 55�C since fluctuations in the water bath occur. The optimum temperature for amylase is 60�C and temperatures above this cause the hydrogen and ionic bonds holding the enzyme amylase's tertiary structure to break. If the molecular structure is disrupted, amylase will cease to function since the substrate molecule i.e. starch will no longer be able to bind with the enzyme. * A buffer solution of pH 7.0, 1cm3 will be used in order to control pH. * A greater number of CuSO4 concentrations will be used 0.000M, 0.050M, 0.010M, 0.015M, 0.020M, 0.025M and 0.030M. * The whole experiment will be carried out three times to provide reliable results. Actual Experiment Apparatus * Amylase solution, 100 cm3, 0.2M * Starch solution, 100 cm3, 0.1M * Copper sulphate solution, 25 cm3, 0.1M * Distilled water, 30 cm3 * Iodine solution 1.0M * 2 10cm3 syringes (each for amylase and starch) and 7 1cm3 (each for the different CuSO4 concentrations) * 9 beakers ( 1 for amylase, 1 for starch and 7 for the different CuSO4 concentrations) * 7 pipettes * 21 test tubes (7 for amylase, 7 for starch and 7 for the CuSO4 concentrations) * 1 test tube rack * Water bath set at 55oC to provide the solutions with a constant temperature * Spotting tiles to monitor the changes in the reaction mixture with iodine. * Buffer solution pH 7, 1cm3- to prevent any fluctuations in pH * Stop clock Actual Method 1. A test tube will be taken into which 1cm3 of 0.0M of CuSO4 i.e. ...read more.


the time taken for iodine to change from a blue black to an orange colour. Different people have different opinions thus have a difference in opinion to when no more colour change is taking place. It was difficult for the human eye to be precise whilst distinguishing between the colour change since the eye can only make a subjective analysis not a quantitative one. A specific apparatus called the colorimeter could have been used to provide me with more accurate data. This method could have been carried out in the exact same way however, the iodine along with the solution would have been placed into cuvettes at regular intervals which would have then been placed into the colorimeter. The reading would have then been noted and repeats would have been carried out. A water bath was used in order to maintain the temperature throughout the experiment. However, the water bath used 11. The time taken for the iodine to change from a blue black colour to the colour of the iodine solution at the start of the experiment i.e. from blue black to an orange colour will be recorded. In order to make my results more reliable I would do the following thing: - I would have more replicates of results for each concentration of the substrate in order to make the results more reliable - I would have a larger variety of concentrations in order to have a larger variety of results. - I would take more readings by extending the time slightly. - Larger test tubes can be used so more substrate can be added lowering the percentage error of the apparatus - Find a method that does not require the bung to be removed and replaced each time as a result stopping the gas loss completely Overall I can say again that the precision and reliability of my results were good. I can prove this as my results proved my hypothesis very well. The error bars on the graph and standard deviation table also proved this was the case. ...read more.

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