"Intestines"

In this experiment starch and glucose molecules are tested to see if it can pass through visking tubing through osmosis.The visking tubing is supposed to act like some artificial intestine(hence the quotations in the title).The set up is as shown below:

The visking tubing has very tiny holes(pores) in it to allow certain types of molecules to pass through during osmosis/diffusion. A starch test and sugar test is conducted at the end of the experiment to test for presence of starch and sugar in the distilled water.

The set up was left untouched for 20 minutes and the distilled water in the boiling tube was poured into 2 test tubes.

Starch Test

For the first test tube a few drops of iodine solution was added into the test tube to test for presence of starch, since iodine solution will turn from yellowish brown to blue black when in the presence of starch.

In the experiment, the distilled water did not turn from yellowish brown to blue black due to the fact that starch molecules are too big to pass through the small pores in the visking tubing.

There is no reaction yet.

Testing for sugar(sugar sugar~)

A few drops of Benedict’s solution (consisting of Copper sulfate, Sodium citrate and Sodium carbonate) was added to the second test tube to test for presence of sugars, in this case glucose. The benedict’s solution will turn from colourless to yellow, green or red (depending on the amount of sugar present) if sugars are present.

This is what the experiment should look like if the test was successful:

(benedict solution turning red)

Just for fun





This was for us to learn how the size of molecules affect the way it passes through the body.

(some photos courtesy of a classmate)