1. Osmosis Diffusion Intro - YouTube
Diffusion/Osmosis
Osmosis Diffusion Intro - YouTube

2. Diffusion: Movement of molecules across a cell membrane
Diffusion requires NO ENERGY
Molecules move from HIGH to LOW concentration.
Let’s see!
Let’s see MORE!

4. Facilitated Diffusion
Many cell membranes have special channels (carrier proteins) that allow molecules to cross it.
These channels help or facilitate diffusion to happen.
This is known as facilitated diffusion.
Like regular diffusion, will ONLY occur if there is a higher concentration of molecules on one side of the membrane.
Let’s see!

6. Osmosis
Osmosis:
Movement of WATER from an area of more water (H) to an area of less water (L)
Water moves OPPOSITE of all other molecules (i.e. solutes)!

7. How does osmosis work? Across a SEMI-PERMEABLE membrane
Only certain molecules, like water, can move freely across the membrane
Water molecules move from HIGH to LOW
They want to BALANCE OUT a solution
Therefore, water moves OPPOSITE of other molecules
Let’s See!

8. salt moves out to balance
Example of Osmosis #1
Condition #1: More Water outside of cell
Inside cell = 98% Water, 2% salt
Outside cell = 100% Water, 0% salt
Water moves into cell,
salt moves out to balance
CELL SWELLS or
BURSTS!

9. salt moves in to balance
Example of Osmosis #2
Condition #2: More water inside of cell
Inside cell: 98% Water, 2% Salt
Outside cell: 95% Water, 5% Salt
Water moves out of cell,
salt moves in to balance
CELL SHRIVELS!

10. Osmotic Pressure
Cells behave differently when placed in different solutions!
This is due to OSMOSIS!
Most cells are ~ 98% water!
Three types of osmotic pressure:
Hypotonic
Hypertonic
Isotonic

11. Hypotonic Condition Cell is placed in 100% water
Solution outside of cell has MORE water, less of other materials (i.e., salt)
Therefore, solution is below strength (hypo)
100%
Water ENTERS cell
98%
CELL
SWELLS!

12. Red Blood Cells in Hypotonic Solution - YouTube

13. Hypertonic Condition Cell is placed in 95% water
Solution outside of cell has LESS water, more of other materials (i.e., salt)
Therefore, solution is above strength (hyper)
Water LEAVES cell
95%
98%
CELL
SHRINKS!

14. Red Blood Cells in a Hypertonic Solution - YouTube

15. Isotonic Condition Cell is placed in 98% water
Solution outside of cell has SAME water, same amount of other materials (i.e., salt)
Therefore, solution is equal strength (iso)
Water moves equally;
Equilibrium exists
98%
CELL
STAYS
THE SAME!
98%

16. Red Blood Cells in an Isotonic Environment - YouTube

17. Review of Osmosis Isotonic, Hypertonic, Hypertonic Animation
You Tube Onion Cell Osmosis

18. Active Transport
Sometimes, materials will move across the cell membrane AGAINST a concentration gradient.
LOW HIGH
This is Active Transport.
THIS REQUIRES ENERGY!!! Just like pulling something uphill!
Cells get this energy from ATP (Adenosine Triphosphate)