Lab Report Plasma Membrane Diffusion

Plasma membranes are selectively permeable. The purpose of this experiment is to reveal how a form of diffusion in a semipermeable membrane works by creating a real life simulation of a semipermeable plasma membrane. This is done by building an imitation of a caterpillar’s digestive tract using dialysis tubing and glassware. The first material in this experiment is a small beaker representing the head and crop of the caterpillar. This beaker is filled with both starch and the enzyme α-amylase. This enzyme digests the starch found in the leaves the caterpillar is eating, which breaks it down into glucose. The opening of the soaked dialysis tubing represents the opening between the crop and intestine, so you fill the tubing with the solution from the small beaker that was just used. You then add the tubing in another beaker that contains water and Lugols reagent. The Lugol’s solution turns a dark blue color when coming in contact with starch, however starch molecules are too large to pass the permeable membrane that crosses the intestine, so it is catalyzed into the smaller glucose molecule by the α-amylase. This should cause no change in the color Lugol’s solution since it does not come in contact with the starch. A control was also added to the experiment that included another dialysis bag in a beaker containing Lugol’s solution, except the dialysis bag only contained starch and no α-amylase. So my hypothesis was that the Lugol’s solution will not turn dark blue because the starch will not be able to cross the semipermeable membraned due to the α-amylase,
It shows that amylase is able to break down starch molecules that are too large to pass through the semipermeable membrane into the much smaller molecules of glucose which are able to permeate through the intestine, or in this case, the dialysis tubing. This was supported when the dialysis tubing did not turn a dark blue