Biology Coursework Enzymes - GCSE Science - Marked by

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Biology Coursework Aim To investigate how starch concentration affects an amylase-controlled reaction. Introduction An enzyme is a protein with a special shape, which catalyses or speeds up chemical reactions inside our bodies. However not all enzymes are proteins. The enzyme amylase that I will be using throughout my investigation to find out how starch concentration affects an enzyme controlled reaction is found in saliva in the mouth and also in the small intestine. Inside the body the enzyme amylase is used to break down the substrate starch into simple sugar (maltose), which is soluble in water. Enzymes are crucial to the existence of humans as it speeds up chemical reactions inside the body, which would be too slow in the absence of enzymes. Enzymes themselves only catalyse chemical reactions and do not alter the actual reaction, they also increase the rate of reaction. Enzymes have many properties which if affected can change the outcome of reactions taking place. When enzymes react the same end product is always formed. Enzymes themselves react best at the optimum temperature of 36.7 �C, as that is the general temperature of our bodies. Also enzymes have optimal pH levels as well at which they react best. The pH at which enzymes work best at is 7 (neutral). However exposure to heat over 40 �C or extreme pH (acid or alkali) can denature the enzyme, which will mean that they can no longer act as a catalyst for the reaction. Temperatures under 36.7 �C will not denature the enzyme but the reaction taking place will be considerably slower. The lock and key theory is a theory in biochemistry that looks at why enzymes catalyse reactions. The theory states that all enzymes have a unique shape and have a special active site on which the substrate attaches itself to and allows the enzyme to begin breaking down the food into products (nutrients). more.

* Then I will place the blue/black starch solution into the test tube rack for ease and safety when adding the amylase to it. * I will then add the amylase to the 1% starch concentration, and immediately start my digital stopwatch. I will stop the digital stopwatch when the amylase turns the starch colourless. * I will then record my results in a table. I will then wash my equipment thoroughly and repeat each concentration twice for accurate and reliable results. I have made a dilution table, which I will follow to help me make the different concentrations. Dilution Table Starch Concentration (%) Amount of starch (ml) Amount of water (ml) 1 2 8 2 4 6 3 6 4 4 8 2 4.5 9 1 5 10 0 Fair Test I will make sure that the experiment I conduct will be accurate and reliable by checking and modifying certain variables before I start my experiment. Variables: Will I keep it constant ? Why ? How ? Temperature (�C) (controlled variable) Yes, I will keep this variable constant as temperature affects the rate of reaction at which enzymes work. If I keep this constant then the

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enzymes will work at the same rate in each experiment. Also if I do not keep the temperature constant then there is a chance that the enzymes can become denatured. I will use a hot water bath to keep the temperature of the water at a constant of 30�C so that the enzymes perform to the closest to there optimum temperature of 37�C (Body Temperature) Concentration of starch (%) (Independent variable) I will not keep this variable constant, as I have to change it for my experiment to be able to be conducted. By changing the concentration of the starch by adding more/less water and more/less starch I will be able to change the percentage of starch.. more.

A second person would be able to start the stopwatch immediately whereas I had to try and pour the amylase into the starch and also at the same time try and start the stopwatch. All of these improvements would increase the reliability and accuracy of my results ensuring a better outcome Also I did not have any anomalous results as visible by looking at my graph. Conclusion In conclusion I personally think that the investigation was very successful. The predictions that I made proved to be right. I think that the reason my predictions proved to be right were partly because of the insight information I had received from the preliminary work I conducted, this helped me very much. Also my Introduction (see above) also led me to my prediction as I based it on the collision and lock and key theory. Also knowing about the properties of enzymes helped me to formulate a prediction. My results proved that as the concentration of starch increases the time taken for the amylase to brake down that starch decreases. It also proved that as the starch concentration increases the rate of reaction increases too I also noticed that there is a positive correlation between the starch concentration and the rate of reaction. This is because as the starch concentration increases there are more successful collisions between the enzyme's active sites and the starch particles creating more products. Enzymes are biological catalyst that speed up reaction. I think that the graphs I drew were quite good as well as they displayed correlation of some sort which backs up the prediction of what my graphs would look like. I think that my graph would have been better if I would have had more points to plot. To conclude I believe that the overall investigation was successful and I was able to investigate how starch concentration affects an amylase-controlled reaction. However I think that the experiment would have been better if the changes I pointed out in my Evaluation (see above) would be carried out. Mustafa Saai, 11P more.

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