Osmosis and Diffusion Via Dialysis Tube

Topics: Starch, Osmosis, Semipermeable membrane Pages: 4 (1961 words) Published: March 12, 2013
Open-ended Lab: Osmosis and Diffusion in Dialysis Tubing Name(s): Background: It is very difficult to measure or see osmosis actually occurring in cells because of the small size of most cells. However, if an artificial membrane that acts in some ways like a real plasma membrane could be found, than a study of osmosis using a model cell would be possible. Dialysis tubing is a manmade semi-permeable membrane that is used to treat people who have kidney failure. Dialysis is a process where substances in solution are separated by their difference in molecular weight (size). The driving force behind dialysis is the concentration difference between two solutions on opposite sides of the membrane. Materials: (per lab team) • 250 ml beaker • 1- 10 cm length of Dialysis tubing (soaked in warm water) • 2 pieces of Cotton string 10 cm long • 15 ml Starch solution with transfer pipette Procedure: 1. Gather one piece of dialysis tubing and two pieces of string. 2. Under gently running water rub the tubing between your fingers until it opens up to form a tube. !!!BE GENTLE DIALYSIS TUBING IS EASILY TORN!!! 3. Once the tubing has opened twist one end shut and tie a knot at least 2 cm from the edge. 4. Fold the tail upwards and tie a second knot. 5. Fill the tube with water and check for any leaks. 6. If no leaks are found empty the tube and fill it with 5 cm of starch solution. 7. Add one pipette full of glucose solution to the tube. 8. Twist the top end of the tube shut just above the surface of the starch-glucose solution and tie a knot. 9. Fold the tail over and tie a second knot. 10. Rinse the tubing off under gently running water. 11. Cut off any remain string 12. Fill your 250 ml beaker to the 150 ml line with tap water. 13. Place the tube in the beaker and add water if necessary to cover the tube. 14. Add several drops of iodine so that the color of the water in the beaker turns orange. 15. Use masking tape to label your beaker with your group name and period #. 16....
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