CIE IGCSE Biology

Revision Notes

5.2 Enzyme Investigations

Enzyme Investigations

  • Amylase is an enzyme that digests starch (a polysaccharide of glucose) into maltose (a disaccharide of glucose).
  • Starch can be tested for easily using iodine solution.

 

Using iodine to test for starch, IGCSE & GCSE Biology revision notesUsing iodine to test for starch

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 Activity

  • 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.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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