Cellular Transport - Sect. 8.1

1. Cellular Transport - Sect. 8.1 • Diffusion –netmovement of particles from an area of higher conc. to an area of lower conc. -The movement is due to the random movement of molecules called Brownian movement.

2. -Diffusion does not cost the cell any energy Click here for web animation

3. Results of diffusion : Dynamic Equilibrium -equal concentration of materials has occurred -continuous movement occurs but no net change Rate of diffusion: depends on and can be changed by: 1. Temperature 2. Concentration gradient 3. Pressure 4. Surface area

4. Osmosis- Diffusion of water across a selectively permeable membrane(does not cost the cell any energy) Three types of solutions involved with Osmosis: • Isotonic solution: -a solution in which the conc. of water outside the cell is the same as the conc. inside the cell. -Cell size stays the same. -no net movement of water occurs The cell is in dynamic equilibrium– no net change

5. Isotonic Solutions Inside the Cell Outside the Cell

6. 2. Hypotonic solution: -solution in which the conc. of water ishigher outside the cell than the conc. of water inside the cell. -water moves into the cell and the cell swells. Example: Red Blood cell in distilled water

8. When cells swell they develop internal cell water pressure called turgor pressure. --cell walls of a plant prevent the plasma membrane from bursting.

9. Animal cells: --no cell wall --can burst from increased turgor pressure --unicellular animals have a contractile vacuole (an adaptation to pump out excess water).

10. Hypotonic Solution Inside the Cell Outside the Cell

11. 3. Hypertonic Solutions: -solution in which the conc. of water is lower outside the cell (less water) than the conc. inside the cell (more water) ---water will move out and the cell will shrink. Example: Red blood cell in saltwater Vegetables in salt water Plasmolysis – loss of water from a cell resulting in a drop in turgor pressure and a decrease in cell size.

12. Hypertonic Solution Inside the Cell Outside the Cell

13. Normal In hypotonic solution In hypertonic solution

14. Passive Transport --**Requires no energy from the cell** --Materials move from area of high conc. to low conc. (down hill) Examples: Diffusion Osmosis of Water Facilitated Diffusion

15. In Diffusion and/or Osmosis, materials can: 1. Move directly through the plasma membrane unaided 2. Move through Channel or Transport Protein which acts like a pore

16. In Facilitated Diffusion, a carrier protein helps the material move across the membrane. The material is still moving from high conc. to low conc. --The carrier protein usually helps the material diffuse faster than would normally occur

17. Active Transport **Requires Cell Energy** **Moves material from a lower conc. to a higher conc.(up hill!!!) ** Examples: --Transport protein that pump ions from low conc. to high conc. across the cell membrane --Endocytosis and Exocytosis

18. Endocytosis --a process in which a cell surrounds and takes in material from its environment --the material is now surrounded by a cell membrane-derived membrane • Phagocytosis – taking in solids • Pinocytosis - taking in liquids • Receptor-mediated endocytosis – cell’s take in specific materials that attach to surface proteins

19. Endocytosis Animation endo = inside cyto = cell Endocytosis

20. Exocytosis- process in which a cell expells wastes or other materials from the cell • Membrane-bound vesicle fuses into the plasma membrane releasing it’s contents Inside the Cell Outside the Cell

21. Exocytosis Animation exo = outside cyto = cell

22. Fluid Mosaic Model #2