Question

Soak one length of dialysis tubing (see image) in water for about 5 minutes. Using clean hands, rub one length of soaked dialysis tubing between your fingers to coax the tube open along the full length of the tube. This will make it easier to fill later. Tie off the bottom end of the dialysis tube with string. Make it tight enough to prevent leakage.

2. Fill a glass with water and use one glucose strip to test for the presence of glucose. This should be negative (see image). Save this glucose strip to use in Step 4.

3. Add ½ tsp or ½ the glucose packet to the colored water in the falcon tube prepared in the previous demonstration. Mix to dissolve the glucose completely.

4. Use the same test strip as in Step 1 to check for the presence of glucose in the falcon tube. This should be positive.

5. Transfer the colored glucose solution from the falcon tube into the dialysis tube that is tied at the bottom and carefully tie it tightly at the other end leaving some air space at the top. It should look like this:

6. Place dialysis tube in the glass filled with water from step 2 and wait 30 minutes (start the last experiment while you wait).

7. After 30 minutes, use the second glucose strip to check for the presence of glucose in the water the tubing is submerged in.

8. Describe the color of the glucose strip. Is it positive or negative for the presence of glucose?

9. Using what you have learned about diffusion and the semi-permeable nature of dialysis tubing, how would you explain these results? You can submit a picture to help answer the question if you choose.

Answer 1

8. Glucose strip will test positive for the presence of glucose. Based on the amount of glucose diffusion, green to brown coloration can be observed in the test strip.

9. Dialysis tube is made of semipermeable membrane. It allows smaller molecules to pass through by diffusion. It also allows water to pass thrugh it by osmosis. Both processes, osmosis and diffusion are passive transport processes Which means they transport materials from where they are more to where they are less without using energy to distribute the materials equally and uniformly.

The dialysis tube is filled with a solution having glucose. Outside the tube , there is no glucose. Because of this glucose will diffuse in to the water outside the from dialysis tube.