1. Doesn’t require energy
The Plasma Membrane
9/18/2018
Simple Diffusion
Doesn’t require energy
14.) Moves materials from high to low concentration
For example: Oxygen and water diffuses into a cell, while carbon dioxide diffusing out.
G. Podgorski, Biol. 1010

2. The Plasma Membrane
9/18/2018
Simple Diffusion
In other words, molecules move from crowded to less crowded areas of concentration.
This can occur in solids, liquids, and gases.
G. Podgorski, Biol. 1010

3. Diffusion “in action”…
You might smell perfume when you sit near or walk past someone wearing it. This is because the perfume molecules are randomly moving throughout the air .
The molecules are going from an areas that is crowded (such as inside the bottle) to a less crowded area (such as the air itself).
There’s more space for the molecules to spread out and move in the air.
Diffusion stops once there is an equal number of molecules in both areas.
The molecules are in equilibrium.

4. The Plasma Membrane
9/18/2018
DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
G. Podgorski, Biol. 1010

5. Diffusion of Liquids The Plasma Membrane 9/18/2018
G. Podgorski, Biol. 1010

6. Diffusion across a membrane
The Plasma Membrane
9/18/2018
Osmosis
Diffusion across a membrane
16. Diffusion of “water” across a cell membrane
Moves from HIGH water potential (low solute) to LOW water potential (high solute)
sem-i-permeable
membrane
G. Podgorski, Biol. 1010

7. Click on Picture for Animation

8. “Facilitated diffusion” *What does the word facilitate mean?
The Plasma Membrane
“Facilitated diffusion”
*What does the word facilitate mean?
9/18/2018
17.) Doesn’t require energy but still needs help! It uses transport proteins to provide “doorways” to help move material from high to low concentration
Examples: Glucose (sugar) or amino acids (--a chain of proteins) moving from blood into a cell.
G. Podgorski, Biol. 1010

9. Facilitated Diffusion
The Plasma Membrane
9/18/2018
Facilitated Diffusion
Molecules will spontaneously move through the pores of the cell membrane with the help of “Channel Proteins” that provide a “doorway”
G. Podgorski, Biol. 1010

10. Facilitated Diffusion
The Plasma Membrane
Facilitated Diffusion
9/18/2018
Carrier proteins do not extend through the membrane.
They bond and drag molecules through the lipid bilayer and release them on the opposite side.
G. Podgorski, Biol. 1010