1. Agenda
Collect Pre-lab #6 – Diffusion
Lab quiz #5

2. Experiment B: Diffusion of molecules through a selectively permeable membrane
Dialysis tubing = selectively permeable membrane
Permeability based on molecular size

3. Experiment B: Diffusion of molecules through a selectively permeable membrane
Secure one end of the dialysis tubing by tying it with string
Add 4 pipettes full of of glucose to bag
Add 4 pipettes full of of starch to bag
Tie bag shut.

4. Experiment B
Place in beaker containing water and several droppers full of iodine
What does iodine test for?
Monitor for color change over 45 minutes
Perform Benedicts test on solution in the bag, and solution outside of bag

5. Experiment B - NOTES
Use labeled pipettes – make sure you don’t mix them up, or you’ll get contamination!!
Dispose of benedict’s waste in appropriate container

6. Part 3: Osmotic Activity in Animal Cells
Put blood cells in different solutions of salt
Observe cells IMMEDIATELY after placing in salt solutions
NOTE: Blood needs to be in fridge when not in use
NOTE: Dispose of blood slides in bleach solution

7. Part 4: Osmotic Activity in Plant Cells
What’s different about plant cells compared to animal cells?
Observe plant cell under 4% salt solution
WASH SLIDES!!

8. Part 5: Molecular Weight DEMO
Make a hole in an agar plate
Add drops of potassium permanganate or methylene blue
Observe after 30 minutes and 1 hour