Digestion and Membrane Permeability Investigation

Membrane Permeability and Dialysis Tubing Dialysis tubing is a selectively permeable membrane used to separate large molecules from small ones. It is often used in diffusion demonstrations. How is dialysis tubing a good model for absorption in the small intestine?

Your goal: Design an experiment to test the permeability of dialysis tubing

Materials Available Tests Available 30cm of dialysis tubing Beakers String Funnels Graduated cylinders Water Milk Lactase Coca Cola Sugar Corn Starch Good ol’ observation Glucose test Strips or Benedict’s Starch test pH Test

Tests for glucose Place approx. 1 ml of test solution into a vial Benedict’s test Glucose Test strips Place approx. 1 ml of test solution into a vial Add 2 ml (10 drops) of Benedicts solution Heat the vial in a hot water bath for 3 to 5 minutes Remove vial and let cool. A color change is a positive test for monosaccharides. Dip the test strip into the solution. Wait a few minutes then compare the color of the test strip to the bottle. Only 2 per group!

Test for starch Add the solution you would like to test to a beaker Add a few drops of Iodine to the solution It will turn dark purple as it complexes with starch.

pH test Dip the end of the pH test strip into the solution. Wait a minute and compare the color of the strip to the container.

What your lab report needs to include: Title Method and procedure- What exactly are you going to be doing? Prediction- What do you think will happen? Hypothesis- What is your explanation for your prediction? Data- What did you observe?