1. DIFFUSION IS...
The net movement of molecules from areas of higher concentration to areas of lower concentration.
Before moving on, ask yourself, “Self, do I know what net movement of molecules means?”
Your face here

2. DIFFUSION IS...
“Passive” - meaning that the cell does not have to use energy to have diffusion happen
Before moving on, ask yourself, “Self, can I justify which graphic best illustrates passive transport?”

3. IN DIFFUSION, THE PHOSPHOLIPID BILAYER MUST BE...
… permeable to the particle.
In the case of the cell membrane, permeable molecules are usually small, non-charged particles like oxygen and carbon dioxide

4. RATES OF DIFFUSION DEPEND ON...
concentration of the diffusing molecule
The greater the difference in concentration between two areas, the greater the rate of diffusion ∴ direct relationship
temperature
The greater the temperature, the greater the rate of diffusion because temperature increases the rate of molecular movement ∴ direct relationship
pressure
The greater the pressure, the greater the rate of diffusion because pressure increases the rate of molecular movement ∴ direct relationship

5. Example: Diffusion of CO2 and O2 into and out of lung alveoli
Watch this 1:34 minute video
Add red dots to illustrated the movement of oxygen gas.
Add blue dots to illustrated the movement of carbon dioxide gas.
Be sure to correctly show movement from areas of higher to lower concentration!

6. Example: Diffusion of CO2 and O2 into and out of eye cornea cells
The cornea is the transparent front part of the eye that covers the iris and pupil. Because the cornea must be transparent (so light can pass through), the cornea does not have blood vessels. But, the cells of the cornea are alive and must receive oxygen and get rid of carbon dioxide waste.
How can this happen? You guessed it… the cornea receives nutrients via diffusion from the tear fluid through the outside surface and the vitreous humour (eyeball juice) through the inside surface.
Think about the implications for people who wear contact lenses…
If you can handle it, watch this video of a cornea transplant

7. SIMPLE DIFFUSION
Add a caption for the graphic. Include the following words:
energy
time
concentration gradient
cell membrane
solute