1. Cellular Transport

2. Diffusion
Osmosis

3. Diffusion = “high to low is the way to go!”
Quote from Billy S. 
Osmosis = is the net movement of water
from a region of high water concentration
through a semi-permeable membrane to
a region of low water concentration. This
movement of water is driven by a difference
in solute concentrations on the two sides
of the membrane

4. A Hypertonic Solution has a higher solute
concentration than the solution to which it
is being compared. A hypertonic solution
is the solution with the higher
concentration of solutes.
A Hypotonic Solution has a lower
solute concentration than the solution
to which it is being compared. A hypotonic
solution is the solution with the lower
Isotonic solutions have the same
solute concentrations. The solutions
being compared have equal concentration
of solutes.

5. In the Lab

6. Red Onion Cells Question: How do tap water and salt water solution
surrounding a red onion cell influence osmosis?

7. Materials: red onion epidermis, forceps or fingernails,
dropper, tap water, salt solution, paper towels, microscope,
slide, and cover slip

8. Make a wet mount of the red onion epidermis.
…The purple pigment is concentrated in the top layer.
…It is not easy to peel off a THIN red onion skin.
…Too thick and the osmostic action will not be observed
because too many cells crowd the slide—layer upon layer.
…A thin skin curls up on itself and must be placed flat against the slide—
or again, too many cell layers will impede the osmotic observation.
…Be careful flattening the skin so that you do not rupture the cells
in the process and lose the purple pigment.

9. Step 1: Obtain a clean slide
Use forceps or fingernails to peel away a single cell layer
(purple region) add a water drop covering the onion cells
Step 3: Place a cover slip over
the onion cells

10. Examine under low power.
…Find few pockets of intact cells with purple inside.
…Focus your work on these cells.
…When you have a clear view switch to medium power.
Cell membrane
at the edge of
the purple
Cell Wall
Yellowish area
Make a labeled drawing, (SketchA) time viewed, title, name of cell, magnification viewed, and short description.  This will give you a record of the original appearance of the onion cells.

11. Take a dropper and add several drops of salt solution
to one side of your cover slip while placing
a small piece of paper towel
along the opposite edge of the cover slip.
The paper should draw out the water
and draw in the salt solution.
Observe the effects of the sodium chloride
(salt) solution on the onion cells.
Salt water
Paper
towel
Slide
Coverslip
Onion cells

12. Plasmolysis Animation
Red Onion Cell
Plasmolysis Animation
Animation Plasmolysis
Elodea
Osmosis Tugor
Animation

13. Plasmolysis Once the salt solution (hypertonic) baths the red onion
cells (hypotonic cytoplasm), the net movement of water
is from the hypotonic cytoplasm of the red onion cells
toward the hypertonic salt solution surrounding the red
onion cells. The cells’ cell membrane pulls away from
the cell wall as noted by the edge of the purple pigment.
Plasmolysis
Make a properly labeled, careful drawing (SketchB) of the cells' appearance
in a second sketch. Time viewed, title, name of cell, magnification viewed, and short description. 
This will give you a record of the appearance post-salt solution.

14. Question: What will occur when the red onion cells are bathed in
tap water?
TAP water
Paper
towel
Slide
Coverslip
Onion cells
Make a properly labeled drawing (SketchC) of the cells' appearance after replacement
with the tap water. Time viewed, title, name of cell, magnification viewed, and short description. 
This will give you a record of the appearance post-salt solution.