1. Section Objectives Explain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells.

2. TYPES OF TRANSPORT PASSIVE TRANSPORT: movement of material from an area of high concentration to an area of low concentration with no energy involved. ACTIVE TRANSPORT: movement of material from an area of low concentration to an area of high concentration to maintain a specific concentration of material inside or outside of the cell – requires energy.

3. PASSIVE TRANSPORT Two types : Diffusion – passive transport or any substance from a high concentration to a low concentration Osmosis – passive transport of water from an area of high concentration to low concentration. What is the effect of osmosis on plant and animal cells?

4. Osmosis: Diffusion of Water Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. In a cell, water always moves to reach an equal concentration on both sides of the membrane.

5. Osmosis: Diffusion of Water The diffusion of water across a selectively permeable membrane is called osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell. Homeostasis – maintaining a stable internal balance.

6. What controls osmosis? Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. Before Osmosis After Osmosis Selectively permeable membrane Water molecule Sugar molecule

7. Osmosis: Diffusion of Water Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.

8. Cells in an isotonic solution isotonic solution- (= concentrations) the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

9. Cells in an isotonic solution water molecules move into and out of the cell at the same rate, and cells retain their normal shape. H2OH2O H2OH2O Water Molecule Dissolved Molecule

10. Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution. Concentration of dissolved substances is the same inside and outside of the cell

11. Cells in a hypotonic solution hypotonic solution: dilute solution thus low solute concentration In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

12. Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases. (plants prefer this – it makes the leaves firm) This happens when the environment outside the cell has less dissolved substances than inside the cell. Water moves in and the cell swells.

13. Cells in a hypertonic solution hypertonic solution: concentrated solution, thus a high solute concentration In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink when there is more water inside the cell as compared to outside the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

14. Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall. PLASMOLYSIS

15. Passive Transport When a cell uses no energy to move particles across a membrane passive transport occurs Particles go DOWN their concentration gradient ( high to low) Diffusion & osmosis are passive transport. Concentration gradient Plasma membrane

16. Passive Transport by proteins Passive transport of materials across the membrane using transport proteins is called facilitated diffusion. Channel proteins Concentrati on gradient Plasma membra ne

17. Passive Transport by proteins Some transport proteins, called channel proteins, form channels that allow specific molecules to flow through.YouTube - Passive TransportYouTube - Passive Transport

18. Active Transport active transport :Movement of materials through a membrane against a concentration gradient and requires energy from the cell. Concentration gradient Plasma membrane Carrier proteins Cellular energy

19. How active transport occurs a transport protein called a carrier protein first binds with a particle of the substance to be transported. Each type of carrier protein has a shape that fits a specific molecule or ion. http://www.youtube.com/watch?v=1ZFqOv xXg9M&feature=related

20. Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. The material is engulfed and enclosed by a portion of the cell ’ s plasma membrane. resulting vacuole with its contents moves to the inside of the cell Exocytosis is the expulsion or secretion of materials from a cell. Exocytose Endocytosis