Amylase and starch

Amylase is an enzyme found in saliva. It digests (hydrolyses) starch to maltose. Maltose is
a reducing sugar.

Today in the lab, we are investigating the effect amylase has on starch.

We detect starch with iodine solution.

  1. Measure 5 cm3 of starch suspension into a test tube. ( test tube S )
  2. Measure 5 cm3 of amylase solution into another test tube. ( test tube A )
  3. On a tile test mix a drop of starch with a drop of iodine solutio to see the colour change. ( brown to blue back)
  4. Place 1 drop of iodine solution every 5 cm and label them 1 to 10
  5. Put the contents of test tube A into test tube S.
  6. Start a stop watch to record time.
  7.  Aft er one minute, dip a glass rod into tube S and then dip the end of the rod into the
    fi rst drop of iodine solution. Record the colour in a table. Repeat  every minute, using a clean rod each time, until you find abscence of starch ( colour change to blue back does not happen any more, starch has beeb broken down to maltose which is not detected with iodine solution.
  • How much time was necessary for the enzyme to breakdown starch completely?
  •  Explain why the iodine solution sometimes turned black.
  •  Explain why the iodine solution sometimes stayed brown.
  • Amylase hydrolyses starch to produce maltose. How could you carry out a test to
    check for the presence of maltose?
  •  Describe some of the sources of error in your experiment. For each one, suggest how  the experiment could be improved.
  • Describe  how you would test the effect of temperature on the activity of amylase.
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