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Substances called catalysts can speed up many chemical reactions.

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Substances called catalysts can speed up many chemical reactions. Enzymes are biological catalysts and were discovered by the German chemist Edward Buchner. Enzymes can be divided into two groups intracellular and extra cellular. Intracellular occur inside the cell where they control metabolism. The latter are produced by cells but achieve their effects outside the cell they include the digestive enzymes that breakdown food. Enzymes are always proteins and their characteristics therefore reflect the properties of proteins. Their main properties are as follows 1. They generally work very rapidly. The fastest known enzyme is Catalyse. Found in the tissues it speeds up the decomposition of hydrogen peroxide into water and oxygen. 2. Enzymes are not destroyed by the reactions they catalyse and so can be used again. This property can be explained by examining how an enzyme works. When an enzyme controlled reaction takes place the enzyme substrate complex. With their various bonds held in relation to each other by the enzyme the substrate molecules react together to form an enzyme product complex. This splits into the enzyme unchanged by the enzyme and product. The enzyme unchanged by the reaction can be used again. ...read more.


My graph will look similar to this: Average time (S) Temperature (oC) If I decide to draw a graph showing the rate of reaction as well it would look like this: Rate of reaction (S-1) Temperature (oC) I expect that as the temperature increases, the rate of reaction will also increase. I expect the rate of reaction to double with every 10oC rise in temperature. This is because the molecules, which are reacting, move faster and have more energy at higher temperatures. To calculate the rate of reaction I will divide 1000 by the average time. Obtaining evidence The results that I obtained and recorded during the experiment, testing the relationship between temperature and the rate of the reaction of starch and the enzyme amylase, were as follows: Temperature (oC) Time 1 (s) Time 2 (s) Average Time (s) Rate (S-1) 0 1500+ 1500+ 1500++1500+= 3000+/2 =1500+ 1000/1500+= 0 20 900 720 900+720= 1620/2 =810 1000/810= 1.23 30 375 375 375+375= 750/2 =375 1000/375= 2.67 40 260 240 260+240= 500/2 =250 1000/250= 4 50 315 300 315+300= 615/2 =370.5 1000/370.5= 3.25 60 1500+ 1500+ 1500++1500+= 3000+/2 =1500+ 1000/1500+= 0 Interpretation First of all the average time taken for the starch to be digested in each condition was calculated. ...read more.


I aimed to start the stop clock the exact moment the starch and amylase were mixed together, but I may have been a second or two off. 3. Dropper- I used the dropper to measure out 2 drops of iodine. I found this instrument quite accurate but found myself accedently putting in 1 or 2 more drops than required. I think my results are reliable. I believe this because if you look at my table of results the replication of results are similar but not identical. The only replication, which would cause great concern, was the result at 20oC When I plot my results on the graph there did not appear to be any anomalous results all points fell on the line of best fit. Are my results good enough to convince other people? My answer to this question would be yes. I feel that I have enough evidence to convince other people. In the experiment I obtained five separate, accurate readings of how temperature affected rate and I feel that this is an acceptable amount to support my conclusion above. This conclusion proved that as the temperature of the water increased, the rate also increased up until 40 oC and then decreased rapidly. My curved graph shows this trend. Nicholas Killough - 1 - ...read more.

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