Paper 2- biological molecules

• Practical: Enzymes & pH- background

  • Amylase is an enzyme that digests starch (a polysaccharide of glucose) into maltose (a disaccharide of glucose)
  • The effect of different pH levels on the activity of amylase can be investigated
• Apparatus

  • Spotting tile
  • Measuring cylinder
  • Test Tube
  • Syringe
  • Pipette
  • Stopwatch
  • Buffer solutions
  • Iodine
  • Starch solution
  • Amylase solution
• first half of method

  • Add a drop of iodine to each of the wells of a spotting tile
  • Use a syringe to place 2 cm3 of amylase into a test tube
  • Add 1cm3 of buffer solution (at pH 2) to the test tube using a syringe
  • Use another test tube to add 2 cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette
• second half method

  • Every 10 seconds, transfer a droplet of the solution to a new well of iodine solution (which should turn blue-black)
  • Repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
  • Record the time taken for the reaction to be completed
  • Repeat the investigation with buffers at different pH values (ranging from pH 3.0 to pH 7.0) 
• method


  visual:

  
• Results and Analysis

  • Amylase breaks down starch
  • When iodine solution stays orange-brown, all starch has been digested
  • investigation shows:
  • At optimum pH, iodine stopped turning blue-black+stayed orange-brown within the shortest amount of time
  • because enzyme is working at its fastest rate+has digested all starch
  • At higher or lower pH's (above or below optimum) iodine took longer to stop turning blue-black or continued to turn blue-black for entire investigation
  • because on either side of optimum pH, enzymes start to become denatured+ thus are unable to bind with starch or break it down
• CORMS

  • C - We are changing the pH of the environment
  • O - This is not relevant to this investigation as we aren't using an organism
  • R - We will repeat the investigation several times to ensure reliability
  • M1 - We will measure the time taken for
  • M2 - the iodine to stop turning black
  • S - We will control the concentration and volume of the amylase, iodine and starch solution used in the investigation