1. Passive Transport vs. Active Transport

2. Remember that all cells have … Plasma or cell membranes that are selectively permeable and very fluid…

3. Passive Transport Does not require energy Moves substances from a higher concentration to a lower concentration Moves with the concentration gradient

4. Types of Passive Transport Diffusion Osmosis Facilitated Diffusion

5. Diffusion Movement of matter (particles) from a high concentration to a low concentration Moves particles that are small in size such as … diffusion of particles water oxygen wastes ions Carbon dioxide Food (glucose)

6. Osmosis Movement of water across a membrane from higher to lower concentration OsmosisOsmosis animation

7. How do cells react to different environments? Because cells have cell membranes they will be affected by various concentrations of substances in fluids. (think about the egg experiment) There are three environments a.Isotonic- same concentrations of water in and out of the cell b.Hypotonic- more solute inside the cell than outside the cell c.Hypertonic- more solute outside the cell than inside the cell

8. animations for various environmentsanimations for various environments (click here to observe changes)

9. Facilitated Diffusion Passage of particles across the plasma membrane by means of transport proteins called channel or carrier proteins Used in the movement of small sugars and large amino acids across the cell membrane facilitated diffusion animation

10. Facilitated Diffusion carrier protein

11. Active Transport Requires energy in the form of ATP (adenosine triphosphate) Moves substances from a lower concentration to a higher concentration Moves molecules against the concentration gradient

12. Types of Active Transport Sodium-Potassium pump Endocytosis Exocytosis

13. Endocytosis The membrane engulfs particles and takes in substances from the environment. Part of the membrane breaks away and becomes a vesicle. Phagocytosis: Engulfing food and particles, “cell eating” Pinocytosis: Engulfing liquids, “cell drinking” Examples: large particles, cholesterol, bacteria, oil droplets pinocytosis animation phagocytosis animation

15. Exocytosis The reverse of endocytosis. This is how the cell exports substances and gets rid of wastes. Examples: toxic wastes, hormones, proteins, carbohydrates exocytosis animation

17. An amoeba is a unicellular organism that eats by endocytosis and releases wastes by exocytosis.