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Investigating the effect of enzyme concentration on the hydrolysis of starch with amylase.

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Investigating the effect of enzyme concentration on the hydrolysis of starch with amylase Aim: Investigate the effect of enzyme concentration on the rate of an enzyme-controlled reaction. Using amylase and starch as my example. Introduction: I am investigating the effect of the concentration of the enzyme, amylase on the time taken for the enzyme to fully breakdown the substrate, starch to a sugar solution. The varied variable will be the concentration and all other variables are going to be fixed. The different concentrations will be: 0.5% 0.75% 1.0% 1.5% 2% An enzyme is a class of protein, which acts as a biological catalyst to speed up the rate of reaction with its substrates. Enzymes have the ability to act on a small group of chemically similar substances. Enzymes are very specific, in the sense that each enzyme is limited to interact with only one set of reactants; the reactants are referred to as substrates. Substrates of an enzyme are the chemicals altered by enzyme-catalysed reactions. The extreme specific nature of enzymes are because of the complicated three-dimensional shape, which is due to the particular way the amino acid chain of proteins folds. The three-dimensional contour limits the number of substrates that can possibly react to only those substrates that can specifically fit the enzyme surface. Enzymes have an active site, which is the specific indent caused by the amino acid on the surface that fold inwards. The active site only allows a substrate of the exact unique shape to fit; this is where the substance combines to form an enzyme- substrate complex. Forming an enzyme-substrate complex makes it possible for substrate molecules to combine to form a product. In this experiment, the product is maltose. The 'lock and key' hypothesis explains how enzymes only work with a specific substrate. The hypothesis presents the enzyme as the 'lock, and the specific substrate as 'key'. ...read more.


As the temperature rises, the rate of the catalysed reaction increases proportionally until the temperature reaches the point where the enzymes denature. The rate of reaction steeply decreases as the denaturising continues and becomes complete. Substrate concentration also has to remain constant. If the substrate concentration is low, collision between enzyme and substrate, molecules are infrequent and reaction continues slowly. As the substrate concentration increase, the initial reaction rate is proportional as collision between the molecules becomes more frequent. Graph 4- the effect of increase in substrate concentration of the rate of an enzyme-catalysed reaction. At saturation, further increase in substrate reaction does not affect the rate of reaction. I am going to keep the substrate concentration constant at 1% so the rate of the reaction is not affected. If there are more enzymes than substrate molecules and then substrate is added, the rate of reaction will increase because there will now be more active sites available for starch to be broken up but if there is enough substrate to occupy all the active sites on the enzymes then the rate of reaction will not alter. Therefore, I will use the same amount and concentration of amylase. Enzyme inhibition affects the rate of reaction so must be kept constant. Enzymes combine briefly with their reactants; this makes them vulnerable to inhibition by unreactive moles that resemble the substrate. The inhibiting molecules can combine with the active site of the enzyme but remain bound without change, which blocks off access by the normal substrate. As a result, the rate of the reaction decreases. If the concentration of the inhibitor becomes high enough, the reaction may stop completely. Inhibition of this type is called competitive because the inhibitor competes with the normal substrate for binding to the active site. Some inhibitors interfere with enzyme-catalysed reactions by combining with enzymes at locations outside the active site. These inhibitors rather than reducing accessibility of the active site to the substrate, cause changes in folding and formation that can reduce the ability of the enzyme to lower the activation energy. ...read more.


The index of concentration would then be noted in a table for each sample. I would then plan to determine the range of temperatures to test, the volumes of starch and amylase solutions to use and the concentrations of these solutions after conducting a pilot study. I would use 10cm3 of 2% starch solution and 10cm3 of 0.01% amylase solution in the two initial test tubes for the main experiment. It would prove easier to; before the experiment was started and while the starch and amylase were acclimatising, set up a tile with, iodine drops already on it, in the depressions on the tile. A drop of the solution collected during the experiment could then simply be added to this and the colour noted. I would not note the index of concentration, as this would be impractical, and instead just note down the time after which there was no more starch present in the solution. In order to decide at which point there was no more starch present, maltose solution will be mixed with iodine in a beaker. This provides an indication of what colour the iodine would turn if there were no starch present, but there was maltose, produced by the enzyme. I would conduct the main experiment between temperatures of 20oC and 70oC inclusive. 20oC is the lowest temperature at which the enzyme could function at all effectively and that the enzyme would denature possibly at 70oC and definitely at temperatures above that. The main experiment would be conducted at 10oC intervals between these temperatures in order to obtain a sufficient number of sufficiently dissimilar results. Throughout the experiment, safety precautions would take to ensure that the experiment was conducted in a safe manner: safety goggles and a lab coat would be worn at all times. All parts of the experiment would be undertaken with care, to ensure that there was no spillage. Any spillages of iodine or starch would be washed thoroughly with soap and water. If any starch solution, iodine indicator or amylase were accidentally ingested, medical attention would be sought immediately. ...read more.

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