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Investigating the activity of diastase.

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Investigating the activity of diastase Enzymes are catalysts and increase the speed of a chemical reaction without themselves undergoing any permanent chemical change. They are neither used up in the reaction nor do they appear as reaction products. They provide an alternate pathway with lower activation energy for the reaction, hence speeding up the reaction. Structure of enzymes Enzymes are made up of amino acids linked by peptide groups into proteins chains, which are then folded into a complex three-dimensional structure held together by a number of different interactions including hydrogen bonding, ionic interactions, van der Waals forces and disulphide bridges. Lock and key theory of enzyme action The folding of the protein chains in enzymes produces a binding site (the active site) which is lined with specific groups which form weak interactions with particular areas in the substrate molecule, holding it in place. Often, the binding of the substrate molecule to the enzyme results in the enzyme changing shape, so specific amino acid chains are brought to the region where the reaction will take place. These amino acids can act as proton donors or acceptors, or can provide the correct conditions for the reaction, either polar or non-polar. ...read more.


I will use 4cm3 of 2% starch and 1cm3 of a 2% solution of diastase when investigating pH. When investigating substrate concentration I will use a range of concentrations of starch - from 10% to 1% and 1 cm3 of 2% solution of diastase. Method pH - During the investigation I used 4 cm of 5% starch rather than 4cm3 of 2% starch as in my plan and 1cm3 of a 1% solution of diastase rather than 1cm3 of a 2% solution, as I found the activity of the enzyme had increased from when I did my preliminary work to determine which concentrations and volumes I was going to use. I made up one batch of 5% starch (40cm3 of 10% starch to 40 cm3 of distilled water) to use throughout the investigation. I made 10 cm3 of each of the 1% enzymes (0.1g in 10 cm3 of the buffer solution). These volumes of solution were enough to carry out the whole investigation. Concentration of substrate - I used 2 cm3 of 1% enzyme (0.3g of diastase in 30 cm3 of pH 7 buffer solution) and 4 cm3 of each of the starch solutions. These were diluted from 10% starch with buffer solution i.e. ...read more.


The dots in the dimple trays varied in size and as the trays were used repeatedly the dots faded. Also, I only took samples every 30 seconds - increasing the frequency of the samples as the reaction appeared to be reaching its end point but the end point of each individual reaction was only measured to the nearest 15 seconds. The inaccuracy in the end point was probably the greatest source of error in the investigation. Improvements of the investigation I could try to limit the sources of error further by making the end point more exact. This could be done by using colourimetry or light sensors to determine when the iodine reached a specific shade by measuring light passing through the sample. This investigation only covered pH and concentration of substrate and only a limited range of those factors. To improve the reliability of the results I should take more readings at different concentrations of starch and different pHs to confirm the trends suggested in my results. I would specifically look at higher concentrations of starch, to see if the rate continued increasing linearly and to what point and investigate different pHs, especially around the 2 possible optimum pHs to confirm exactly where the optimum pH range was. In addition the investigation could cover other factors such as effect of temperature and effect of varying the concentration of enzyme on the activity of the diastase. ...read more.

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