1. Diffusion and Osmosis: The Movement of Molecules
-the movement of molecules from an area of high concentration to an area of low concentration
-a form of passive transport (does not require energy)

2. Two Types of Diffusion in Cells:
-Simple diffusion
-Facilitated diffusion
-Simple diffusion:
-Molecules move directly through the cell membrane
-Facilitated diffusion:
-Molecules move through a protein channel (transport protein/ carrier protein) in the cell membrane

3. Simple Diffusion

4. Solute
Protein Channel
Phospholipid
Bi-layer
Diffusion is “helped” by the presence of protein channels. Larger molecules can diffuse through the larger spaces provided by the protein channels.

6. Osmosis
-the movement of WATER molecules across a cell membrane from an area of low solute concentration to an area of high solute concentration
OR (where water is more highly concentrated to where it is lower in concentration)
-a form of passive transport (does not require energy)

7. -Passive transport:
-Does not require energy because it is going with the concentration gradient
-Molecules are traveling from an area of high concentration to an area of low concentration

8. Active vs. Passive Transport
-Active transport:
-Requires energy because it is going against the concentration gradient
-Molecules are traveling from an area of low concentration to an area of high concentration

10. Isotonic, Hypertonic, and Hypotonic Solutions
The medium is the liquid that the object, here a red blood cell, is in
If the medium is hypertonic, that means the medium has more solute than the cell – The cell expels water to equilize the solute concentration
Hypotonic medium means that the medium has less solute than the cell – the cell takes in water to equilize the solute concentration

11. Molecules can diffuse from cells to vessicles and from cells to vesicles:
The Cell is higher in concentration of Oxygen than the vesicle  the oxygen diffuses through the membrane of the cell, through the membrane of the vesicle
The movement of oxygen stops when the cell and vesicle are isotonic for oxygen – when they have the same oxygen concentration
What happens when we breathe?

12. What Happens When We Breathe
Oxygen in our lung cells is higher than the oxygen in the surrounding blood vessels. The oxygen in our lung cells diffuses into the blood vessels and is carried to the cells of all of our organs.
The blood vessels are now higher in oxygen than the cells of the body tissues and can diffuse from the blood vessels to these cells.