CIE IGCSE Biology

Revision Notes

5.1.2 Enzyme Investigations

Test Yourself

Investigating the Effect of Temperature on Amylase

  • Starch solution is heated to a set temperature
  • Iodine is added to wells of a spotting tile
  • Amylase is added to the starch solution and mixed well
  • Every minute, droplets of solution are added to a new well of iodine solution
  • This is continued until the iodine stops turning blue-black (this means there is no more starch left in the solution as the amylase has broken it all down)
  • Time taken for the reaction to be completed is recorded
  • Experiment is repeated at different temperatures
  • The quicker the reaction is completed, the faster the enzyme is working

Investigating the effect of temperature on enzyme activity, IGCSE & GCSE Biology revision notesInvestigating the effect of temperature on enzyme activity

Investigating the Effect of pH on Amylase

  • Place single drops of iodine solution in rows on the tile
  • Label a test tube with the pH to be tested
  • Use the syringe to place 2cm3 of amylase in the test tube
  • Add 1cm3 of buffer solution to the test tube using a syringe
  • Use another test tube to add 2cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette
  • After 10 seconds, use a pipette to place one drop of mixture on the first drop of iodine, which should turn blue-black
  • Wait another 10 seconds and place another drop of mixture  on the second drop of iodine
  • Repeat every 10 seconds until iodine solution remains orange-brown
  • Repeat experiment at different pH values - the less time the iodine solution takes to remain orange-brown, the quicker all the starch has been digested and so the better the enzyme works at that pH

Investigating effect pH on enzyme activity, IGCSE & GCSE Chemistry revision notesInvestigating the effect of pH on enzyme activity

Exam Tip

Describing and explaining experimental results for enzyme experiments is a common type of exam question so make sure you understand what is happening and, for a 7, 8 or 9, can relate this to changes in the active site of the enzyme when it has denatured, or if it is a low temperature, relate it to the amount of kinetic energy the molecules have.

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Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.