effect of pH on enzymes

• Background information

  The activity of biological catalysts (enzymes) are affected by pH. This practical explores how different pH levels affect the activity of amylase, an enzyme that breaks down starch into sugars. Using buffer solutions to alter pH, you will measure the rate of starch breakdown by observing changes in the colour of an iodine solution.
• independent variable

  pH of buffer solution
• dependant variable

  Rate of starch breakdown
• control variables

  Temperature of the reaction, concentration of amylase, concentration of starch, volume of solutions.
• step 1

  place test tubes containing buffer solution, enzyme and starch in a water bath set to 35 degrees Celsius - clearly label each one
• Step 2

  fill each dimple in the spotting tile with iodine solution, once each solution has reached 35 degrees transfer them into one test tube and immediately start a timer.
• Step 3

  Take a zero reading of the solution as soon as the stop watch has started- it should indicate the presence of starch.
• Step 4

  place a few drops of the solution into a different dimple each time every ten seconds. When there is no colour change stop the clock and record the time it took for all the starch to be broken down.
• Step 5

  repeat the whole experiment with a different pH of buffer solution