The Cell Membrane and Passive Transport

1. The Cell Membrane and • Passive Transport

2. cell membrane • The Cell Membrane • made of two phospholipid layers • The cell membrane has two major functions. • forms a boundary between inside and outside of the cell • controls passage of materials outside cell inside cell

3. carbohydrate chain protein cell membrane cholesterol protein protein channel • AKA: Fluid mosaic model • There are other molecules imbedded • All provide a specific function

4. The membrane is “selectively permeable” • Only some molecules can pass

5. 3.4 Diffusion and Osmosis KEY CONCEPT Materials move across membranes because of concentration differences.

6. 3.4 Diffusion and Osmosis Passive transport does not require energy input from a cell. • Molecules can move across the cell membrane through passive transport. • There are two types of passive transport. • diffusion • osmosis

7. Diffusion: Movement of molecules from an area of high to low concentration • Movement continues until equilibrium is reached • Equilibrium: same amount of molecules on the outside of a cell as the inside

8. Diffusion (contd) • Passive transport: No energy required to move molecules • If more molecules outside the cell… they move inside • If more molecules inside the cell…they move outside • Will O2 move into this cell or out of this cell?

9. Diffusion (contd) Where is the high Oxygen concentration? • Passive transport: No energy (ATP) required to move molecules • If more molecules outside the cell… they move inside (and vise versa) Where is the high CARBON DIOXIDE concentration?

10. O2 O2 O2 O2

11. O2 O2 O2 O2 O2 O2

12. O2 O2 O2 O2 O2 O2

13. Where is the HIGH oxygen concentration? O2 O2 O2 O2 O2 O2 Where is the LOW oxygen concentration?

15. O2 O2 O2 O2 O2 O2

16. O2 O2 O2 O2 O2 O2

17. Where is the HIGH oxygen concentration? Where is the LOW oxygen concentration? O2 O2 O2 O2 O2 O2 Cell X gets oxygen through the process of diffusion!

18. The reverse process is true w/ carbon dioxide. CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2

19. Where is the HIGH carbon dioxide concentration? CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2

20. CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2

21. CO2 CO2 CO2 CO2

22. Where is the HIGH carbon dioxide concentration? CO2 CO2 CO2 CO2

23. CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2

24. CO2 CO2 CO2 CO2

25. Osmosis Defined: Diffusion of water from an area of high to low concentration High H20 concentration if: less particles dissolved in the water Low H20 concentration if: more particles dissolved in the water

26. 3.4 Diffusion and Osmosis • There are three types of solutions in osmosis. • isotonic • hypertonic • hypotonic

27. Group Explanation • A cell has been placed into a mystery solution and appears to have shrunken. • Which type of solution is the cell placed in? • What can you conclude about the water concentration inside the cells compared to outside? • What can you conclude about the solute concentration inside the cells compared to outside? • Using your explanation of osmosis, explain why the cell appears to have shrunken.

28. A cell has been placed into a mystery solution and appears to have shrunken. • Which type of solution is the cell placed in? • hypertonic • 2) What can you conclude about the water concentration inside the cells compared to outside? • If the cell shrunk it lost water. This means the cell had a greater water concentration. • 3) What can you conclude about the solute concentration inside the cells compared to outside? • The solute concentration inside the cell is low. I know this because the cell has a high water concentration. The fewer solutes, the higher the water concentration. • 4) Using your explanation of osmosis, explain why the cell appears to have shrunken. • The cell shrunk because it lost water. There was a greater water concentration inside the cell so therefore water diffused out of the cell.

29. 3.4 Diffusion and Osmosis Some molecules can only diffuse through transport proteins. • Some molecules cannot easily diffuse across the cell membrane. • Facilitated diffusion is diffusion through transport proteins.