Starch is a very large molecule made up of many glucose molecules bonded together. Does this help explain the results of this experiment? Explain how.
dialysis tubing with starch and glucose
Dialysis tubing is the experiment to separate the large and small molecules from a solution based on their ability to pass through a semi-permeable membrane.
After passing through dialysing tube, glucose, being smaller molecule, can pass through the tube but the starch molecules can not. We can test for the presence of glucose molecule in the distill water outside the dialysing tube and presence of starch molecules left in the dialysing tube. Presence of Starch can be tested through addition of Iodine drops in the dialysing tube, which will give blue-black colour with it. Glucose, being a reducing sugar, can be tested with Benedict's reagent, which will give brick red or orange colour with it.
Presence of glucose in distill water indicates that it is a small molecule, inability of starch to pass through the dialysing tube indicates that it is a complex molecule.Addition of saliva in the starch group can be used to test the presence of glucose molecules in the starch.