enzymes

• Lower than Optimum Temperature

  • The temperature is (further) away from optimum temperature
  • There is less movement (less kinetic energy)
  • There are fewer collisions and less enzyme substrate complexes are formed
• Higher than Optimum Temperature

  • The enzyme is denatured
  • The active site changes shape and the substrate no longer fits
• Steps of the investigation

  1. Put one drop of iodine solution into each of 12 wells on a spotting tile

  2. Add starch solution into a syringe

  3. Add one drop of starch from the syringe to the first well in the spotting tile and record the colour change

  4. The iodine solution should turn blue/black because starch is present (No amylase was added)

  5. Rinse (clean) the syringe (to remove starch)

  6. Add amylase to the syringe that contains the starch solution

  7. Mix starch+amylase by rocking the syringe for one minute

  8. Add one drop of the mixture from the syringe to the next well in the spotting tile and record the colour change

  9. Add one drop of the mixture from the syringe at intervals of one minute until there is starch and amylase in all of the wells. Remember that all wells contain iodine solution

  10. Repeat the experiment with iodine, amylase and starch that have been stored in a water bath at different temperatures
• The first well is black because there is starch. No amylase was added.
• The second, 3rd, 4th, 5th and 6th wells are black as well because starch is present. The reaction between the enzyme (amylase) and the substrate (starch) was not complete yet and there was starch still left in the wells.
• The reaction took 6 minutes to be complete. The iodine solution stayed yellow/brown and did not longer turn black because there was no starch left. All the starch was digested/broken down by the amylase.
• At higher temperatures


  Starch would be digested sooner/quicker so there would be fewer wells with blue/black colour
• When investigating temperature, pH must be kept constant.
• Changes in pH


  • Can denature enzymes by breaking the bonds that hold their structure in place
  • The pH at which this happens is different for different enzymes, but generally an extreme PH will denature any enzyme (a pH that is far from the optimum pH, which can be both too low or too high)
  • When the enzyme is denatured, the substrate no longer fits in the enzyme´s active site
• This method uses amylase (in solutions of different pH) to break down starch


  1. Same method as 2.12

  2. The reaction can be monitored by using iodine to test the presence of starch in the solution with a continuous sampling method

  3. When investigating pH, temperature must be kept constant

  4. To maintain the temperature of the solution, a Bunsen burner and water beaker must be used