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

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

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.

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

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

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

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!!

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