Enzymes

• Why must samples be left in the water bath before solutions are mixed? To allow temperature to equilibrate
• What is a buffer solution? A solution which can resist changes in pH
• What is the first step in investigating the effect of pH on the rate of reaction of the amylase enzyme?

  Place starch solution, amylase solution, and buffer solution in a water bath at 25°C for a few minutes
• What should you do after combining the starch, amylase, and buffer solutions?

  Add a drop of the mixture to iodine solution on a tile
• How often should you add the mixture to iodine solution drops on the tile during the experiment?

  At fixed 30s intervals until the iodine solution remains brown
• What indicates that the reaction has stopped in the investigation of amylase activity?

  The iodine solution remains brown and does not turn blue-black
• What should you do after calculating the rate of reaction at a specific pH?

  Repeat the experiment at different pH values using different buffer solutions
• What is the final step in the investigation of the effect of pH on amylase activity?


  • Plot a graph of rate (y) against pH (x)
• Rate of reaction = 1 ÷ time taken for the solution ti remain brown