Coursework and practical plan for title "Investigate the effect of temperature on the action of the enzyme diastase on starch."

Essay by Mupple October 2005

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For my investigation, I plan to examine the effect temperature has on enzyme action involving the biological catalyst- diastase, and its substrate- starch. In lesson, I have conducted a preliminary experiment to give me an idea of what to expect and a chance to conduct the experiment before hand. From my preliminary work I believe that an equal amount of substrate (Starch) with an equal amount of enzyme (Diastase) should finish reacting at around 90-120 seconds. Also, I have learned that an enzyme is a globular protein with a tertiary structure of polypeptides- this gives the enzymes their active site shape. I also know how enzymes work- there is the "lock and key" theory which suggests one enzyme for one substrate, with the active site being the correct shape, but also the "induced fit" theory which suggests enzymes are loose and adjust their shape to fit over the substrate.

From my studies I learn that there are factors which affect enzymes- these include pH, temperature, substrate concentration and enzyme concentration. Most enzymes work best at a neutral pH of 7 or a slightly alkali pH of around 8-9. Though there are exceptions such as Pepsin which works best at acidic pH 2. The temperature also effects the enzyme activity- most enzymes are mesophiles which have optimum temperatures of 20-40*C. Others are thermophiles, which are optimum above 40*C, whereas others are psychrophiles which work best below 20*C. Also affecting the rate of reaction is the concentration of enzymes- the more enzymes there are, the more likely the substrate will collide with an enzyme- so the more enzymes available, the faster the reaction. On the other hand if there is more substrate the reaction will be fast for a while, but then the saturation point will occur and the...