The digestive system

Digestion of food in vitro

Digestion of food in vitro



Illustrate the action of amylase on starch.

What you need to know:

  • Bread contains starch (a complex carbohydrate);
  • Iodine solution is a chemical reagent which only changes colour when starch is present;
  • Amylase is an enzyme (present in saliva) which transforms starch into glucose.



Prepare two test tubes with the following mixtures:

  • tube 1: bread + iodine solution + water
  • tube 2: bread + iodine solution + amylase


Leave for 20 minutes and then observe what has happened:

  • The iodine solution in tube 1 has turned blue, showing that it contains starch and that water alone does not transform starch.
  • The iodine solution in tube 2 remains yellow, showing that it does not contain any starch and that the amylase has transformed the starch into glucose.