Diffusion/Osmosis

1. 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. 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. 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)