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The effect of temperature on the hydrolysis of starch using amylase extracted from barley.

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Introduction

Sasha Caddy, RM11. 20/01/04 The effect of temperature on the hydrolysis of starch using amylase extracted from barley Interpretation of results: Enzymes are a class of proteins that catalyse chemical reactions, which increases the rate of a metabolic reaction. Most enzymes are specific, working on a particular or class of reactions. In this case I am using an enzyme known as amylase (a group of enzymes which convert starch to sugar), which is an important metabolic enzyme. Amylase is found in various parts of the body including the saliva of the parotid gland and the pancreas, e.g. ptyalin, which aids in the digestion of carbohydrates by speeding up specific digestive processes taking place from the mouth to the small intestines. However, in this experiment we are using amylase which has been extracted from barley. The function of amylase is to catalyze (to modify the rate of a chemical reaction by catalysis) the hydrolysis (decomposition of a chemical compound by reaction with water) of starch into glucose. Starch is a mixture of two compounds; amylose and amylopectin, both of these molecules are polymers which contain a large, variable number of a-glucose molecules linked to each other by condensation. Amylase acts on starch, which is a polysaccharide (a class of carbohydrates; starch, consisting of a number of twenty-five monosaccharides) and breaks it down into maltose, a disaccharide. A disaccharide is defined as any class of carbohydrates; maltose, that yield two monosaccharides upon hydrolysis. ...read more.

Middle

This causes them to react more efficiently as this results in more enzyme-substrate complexes and in turn the formation of more products. At low temperatures e.g. 15 C, the molecules will not collide very frequently and the starch will not be broken down as quickly. This shown on the graphs at 15 C and at 0 minutes there is 0% transmission from the colorimeter, meaning that 0% of light can pass through the solution because there is 500mg of starch (shown by the 'Starch Calibration Curve'). As time increases to 22 minutes there is a 15% transmission from the colorimeter meaning there is 160mg of starch concentration left in the solution. This is because it has been broken down by amylase at a slow activity rate, so there is a higher concentration of starch left compared to the 25 C (120mg) and 35 C (70mg) results. From the second graph; 'A graph to show the milligrams of starch at minute intervals at different temperatures', it shows that with time, the starch concentration is decreasing for each temperature that is being tested. This graph shows an exponential decay curve of the amount of starch concentration broken down for every x minutes, therefore the substrate will not totally be broken down. This reaction is not a equilibrium reaction because as the starch concentration decreases the enzyme finds it increasingly difficult to find enough substrate to act on. From my results, I can conclude that between temperatures 15 C - 35 C, the efficiency of the enzyme increases with temperature. ...read more.

Conclusion

Another problem with the pipettes is that when the reaction medium was extracted and clearfully put into a diluted iodine solution, during this time the amylase was acting on the starch while this solution was in the pipette. This made the timings recorded slightly out, although this effect may have been lessened with the temperature at 35 C as the mixture was cooling down to room temperature in the pipette. Also we could have possibly swirled the enzyme extract and starch solution together in the water bath so that the substrate and enzyme could mix and the molecules collide. A solution to this whole experiment would have been to automate (convert to a automatic operation) the whole system. This would have allowed a sample of the mixture to be automatically taken every minute or possibly more frequently, and the concentration of the starch stored onto a computer. Carrying out the experiment like this would have solved any inaccuracies in timing, which may not have always been exact when using a stop clock and someone watching the time. This way it would have also removed any human errors e.g. the test tube not being wiped properly before being placed into the colorimeter or didn't shake the reaction medium and diluted iodine solution together enough/too much etc. So if the experiment had use of better apparatus and stricter conditions, my results would have been plotted onto a graph and a more clear and accurate curve would have resulted. In this experiment there were no anomalous results which can be shown from the graphs. ...read more.

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This account includes detailed background theory and good discussion and evaluation sections. However, in places biological terminology might have been used more carefully.

Marked by teacher Adam Roberts 17/09/2013

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