Required practical: a student investigated how temperature affects the activity of the enzyme amylase. At each temperature, she mixed amylase solution with starch solution and used a spotting tile to test a fresh drop of the mixture with iodine solution every few seconds, until the iodine no longer turned blue-black. She recorded the time taken for the starch to be fully broken down at each temperature.
Temperature (deg C): 10, 20, 30, 40, 50, 60
Time for starch to be fully broken down (s): 200, 100, 50, 25, 50, 100
(a)Identify the independent variable and the dependent variable in this investigation.(2)
(b)State two variables, other than temperature, that should be controlled to make this a fair test.(2)
(c)Calculate the rate of reaction at 40 deg C, using rate = 1000 / time taken (in seconds).(2)
(d)Describe the pattern shown by the results as temperature increases from 10 deg C to 60 deg C.(2)
(e)Explain, in terms of enzyme structure, why the rate of reaction decreases above 40 deg C.(3)
(Total for Question 17 is 11 marks)