1. How do molecules move around?
Diffusion is the movement of molecules from a HIGH concentration
to a low concentration

2. Whaddaya mean, molecules MOVE ?????
You gotta be kidding me!
Yeah, right
diffusion animation

3. To go into or out of a cell by diffusion or osmosis (without using energy)
A molecule must be . . .
The right size to pass through an opening
The right shape to pass through an opening
Going from a high to a low concentration

4. Cell membranes must have
Small openings for
small molecules
Medium openings for
medium molecules
And the BIG stuff is a whole other story!!
Oxygen
Carbon dioxide
Water
Glucose

5. Examples: Water Oxygen Carbon dioxide Alcohol
Method of Movement: Diffusion SMALL openings in between phospholipids for small molecules:
Examples: Water Oxygen Carbon dioxide Alcohol

6. Method of Movement: OSMOSIS
Osmosis is the movement of
WATER
from a high to a low concentration
through a membrane

7. Method of Movement: Passive Transport Open ‘protein doorways’ for medium sized molecules
Examples:
Glucose
Amino Acids
Some Lipids
Some Starches

8. Method of Movement: Passive Transport
Materials moving into or out of the cell without using any energy
Examples:
Diffusion
Osmosis
Open protein doorways (channels)
*from a high to a low concentration

9. Method of Movement: Active Transport
Closed ‘Protein Doorway’
for LARGE molecules
Needed for molecules going from a low to high concentration (reverse diffusion)
Active = uses up ENERGY (ATP)

10. Active transport from a low to high concentration – ENERGY

11. Passive Transport: Open protein doorway
Diffusion
Passive Transport: Open protein doorway
Active Transport: Locked protein doorway

12. The Method of Movement: Endocytosis and Exocytosis The BIG
Membrane surrounds particle to form a vesicle which then moves INTO the cell
Exocytosis
Vesicle surrounds particle and moves to membrane and OUT of the cell

14. The cell membrane is “selectively permeable”.=
It controls what enters and leaves the cell.

15. The Cell Membrane “The Fluid Mosaic Model”