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An experiment to investigate the effectof Copper (II) Sulphate on the activity of amylase.

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An experiment to investigate the effect of Copper (II) Sulphate on the activity of amylase Introduction Copper (II) Sulphate is an enzyme inhibitor. An enzyme inhibitor is any substance or chemical which if added to the enzyme substrate complex will decrease the rate of reaction. Inhibitors come in two forms: competitive and non-competitive inhibitors. A competitive inhibitor is one that competes for the active site of an enzyme with the enzymes' substrate. It does not affect the enzyme in any way other than occupy the active site making the productivity of the enzyme less efficient. This can be explained clearly in the diagram below: Competitive inhibitors are reversible, that is the inhibitor does not stay bound with the active site but is released again so the enzyme is still able to form the enzyme-substrate complex. It is summarised in the following equation: Enzyme + Inhibitor Enzyme-Inhibitor Complex Competitive inhibitors are always reversible. Non-competitive inhibition occurs when the inhibitor does not compete with the active site but binds to another part of the enzyme changing its shape, thus denaturing a part of the enzyme. Non-competitive inhibitors can be reversible or irreversible (however irreversible inhibitors are always non-competitive). Irreversible inhibitors act as in the equation above, but do not have a double arrow but one arrow indicating that the reaction occurs one way. This can be shown diagrammatically below. Copper (II) sulphate is an inhibitor and depending upon what it affects is competitive or non-competitive. For example with trypsin, copper (II) sulphate is a competitive inhibitor. However, in this experiment we are dealing with amylase, and copper (II) sulphate is in fact a non-competitive inhibitor of this enzyme. The inhibiting component of copper (II) sulphate is the Cu2+ ion (although the SO42- component can also cause inhibition if it is in high enough concentrations). The reason it is a good inhibitor is because of a few reasons. ...read more.


That is Q10 = 2 (between 0oC and optimum) For example if the rate was 5 at temperature X then 10oC above the temperature of X the rate would be 10. However this trend will not continue forever. Eventually as you increase the temperature, the kinetic energy of the molecules increase, but at the same time the bonds of the molecules begin to break. If the bonds (i.e. the covalent bonds holding the molecule together) of the enzyme, (e.g. amylase) begins to break, then the shape of the enzyme changes due to unfolding and therefore the substrate (e.g. starch) will no longer be able to fit in the active site of the molecule and so no digestion occurs. This is the point where the enzyme is said to have denatured So we find that the rate of reaction keeps increasing up until the point where the bonds of the enzyme begin to break, after this point the rate of reaction decreases again. There must be an optimum point as shown in the diagram below: If the experiment were conducted at this temperature, which happens to be around 50oC, then the rate of reaction would be significantly increased, to be precise around 6 times as fast. As all of the chemicals, i.e. copper (II) sulphate solutions, amylase and starch will take place in this environment, then 50oC will become a constant. This will have no overall effect on the experiment other than to increase the rate by the same amount each time. The variability would come about only due to the concentrations of copper (II) sulphate. Another factor that could improve the set of results is when to put the iodine solution into the mixture. The dark blue colour is produced by iodine binding onto the starch. As this could cause a change in the shape of starch, it is likely to cause an interference with the activity of amylase. ...read more.


sulphate on the activity of amylase. It was important to repeat the results in order to get a more accurate overall result. The more times the experiment would be repeated the more accurate the results are likely to be. The main flaw of this experiment was to judge when the enzyme had finished digesting the starch. It was very hard to make an accurate decision when the end point was. This was due to the fact that it was up to the individual to decide when the reaction was over. Even though a test-tube containing the relevant colour the solution should change back to was placed beside, it never went precisely that colour. It was especially harder in the longer reactions, such as the 1.0molar solution of copper (II) sulphate as the colour change was very long and the solution changed from dark blue to blue (due to the colour of the copper (II) sulphate). Another limitation was the adding of the iodine. Iodine binds onto starch thus forming the dark blue colour. The reaction needed to have the iodine added near the start, as the change from dark blue to colourless had to be seen. However, as iodine binds onto the starch, there would always be some of the starch molecule left undigested and so a faint dark blue colour would be left. As the copper (II) sulphate was made to a 1.0 molar solution, all the other concentrations had to be made from the 1.0molar solution. This too would prove an inaccuracy, as there would be a variation between the concentrations made and tested each time. However, the experiment did yield satisfactory results in respect with what the hypothesis suggested. In this aspect the experiment was successful, even though there were inaccuracies in the method. Further experimentation could be done by firstly using a colorimeter to detect the colour changes of the solution as the starch is being digested. This would yield increased accurate results. The experiment could be extended to see whether alpha amylase would be inhibited more or less than beta amylase using copper (II) sulphate. ...read more.

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