1. Agenda Collect Pre-lab #5 – Diffusion. Lab quiz #4.
Lab 5 Today on Diffusion & Osmosis.
Microworld samples for today: sheep blood and Elodea?
Paper Assignment due next week!
In 2 weeks you will also design an experiment on fermentation.

2. The Paper Assignment
Obtain the Paper Assignment from either your instructor or the lab web page. It is an assignment to help you understand the makeup of a scientific paper or article
It is due in a week.
Follow the directions and then answer the questions.
In two weeks you will make an Informal Lab Report on an experiment you will design with your lab group.

3. A Lab Report Has: A Title An Introduction section
A Materials and Methods section
A Results section
A Discussion (or discussion/conclusion) section
A References (or Literature Cited) section
See an example report in Appendix A of your lab manual
Your Paper Assignment should help you learn the above and help you understand how to write an informal lab report which you will do in 2 weeks!

4. Experiment 1: Diffusion of molecules through a selectively permeable membrane
Dialysis tubing = selectively permeable membrane
Permeability based on molecular size so it differs from the permeability of a cell

5. Experiment 1: 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 glucose to bag (5-10 ml)
Add 4 pipettes full of starch to bag (5-10 ml)
Remove air & tie the bag shut. Helps if two work together.

6. Experiment 1 Wash the bag well. Dry it and record its weight.
Place in beaker containing water and several droppers full of iodine.
What does iodine test for?
Monitor for color change over 45 minutes.
Glucose solution

7. Experiment 1 After 45 minutes:
Make observation about starch diffusion.
Wash & weigh the bag, testing for osmosis.
Perform Benedicts test on solution in the bag, and in the beaker to test for glucose.
Glucose solution

8. Exercise 2 – Brownian Motion
Using Carmine Dye to observe Brownian motion
Is a powder of particles that are tiny enough to move when a water molecule collides with them.
Best if you use a nearly invisible amount
Handle w/ care, Carmine Dye tends to go everywhere!

9. Exercise 3: Osmotic Activity in Plant Cells
What’s different about plant & animal cells?
The cell wall protects a cell in hypotonic soltions.
Observe plant cell under 4% salt solution, best to observe as you add the salt and see what happens!
WASH & put slides away!!

10. Exercise 4: Osmotic Activity in Animal Cells
Put blood cells in different solutions of salt.
Observe cells IMMEDIATELY after placing in each solution!
NOTE: Blood needs to be in fridge when not in use.
NOTE: Dispose of blood slides in bleach solution!

11. Exercise 5: Molecular Weight DEMO
At my desk there will be an agar plate with a drop each of 1.5% potassium permanganate and 3.5% methylene blue.
Observe after 30 minutes to 1 hour to compare the effect of molecular weight on diffusion.
Which do you expect to move faster, the bigger or smaller molecular weight? Which is smaller?
One problem w/ this experiment is that they are at different concentrations. Which dye do you expect to diffuse faster by the concentration?

12. Using the Oil Immersion Lens Today!
Start focusing using lowest power (4x)!
Switch to the next higher objective
Do NOTuse the Coarse Focus Knob after 4x!
Use ONLY the Fine Focus Knob to bring the slide into focus!
Continue this procedure till you come to 100x

13. Using the Oil Immersion Lens
To add oil, move the lenses half-way between 40X and 100X lenses
Add a very small amount of oil (less than 1 drop)
Click the 100X objective into place
Do NOT move back to 40X, or you’ll get oil on it!
If using oil, you must clean it
Use only lens paper & lens cleaner on lenses!

14. Oil Immersion Oil has a similar refractive index as glass
Keeps light rays from bending going through sample
Increases resolution
100x w/o oil is worse than the 40x 14