1. Ch 5 Homeostasis and cell transport

2. How do cells get the things they need?
How do they get rid of their wastes?
How do cells transport stuff?

3. 5-1 Passive transport
Materials must be able to cross the cell membrane
Some don’t require energy input: Passive transport
Diffusion: movement of particles from area of high to low concentration

4. Diffusion
Two solutions can have different concentrations of solute (particles)
Concentration gradient: the difference in concentration of molecules
Diffusion driven by kinetic energy
Molecules are in constant motion
Diffusion occurs until equilibrium is reached

5. Diffusion across membranes
Diffusion across a membrane is called simple diffusion
Not everything can diffuse through a membrane
Limits include
Size
polarity

6. Osmosis
Osmosis: process by which water molecules diffuse across a membrane from an area of high to low concentration
Form of passive transport
Direction of movement depends on relative concentration of solutes in solution

7. Direction of osmosis
If concentration of solutes outside of cell is lower than inside the cell, the solution outside is hypotonic
Water diffuses into cell
Animal cells can lyse (burst)
If concentration of solutes outside the cell is higher than inside, the solution outside is hypertonic
Water diffuses out of cell
Plasmolysis (cell shrinks)
When concentrations are equal: isotonic
Equal movement into and out of the cell

9. More osmosis stuff
Turgor pressure: pressure that water exerts against plant cell wall
Page 99: contractile vacuoles: remove excess water Q

10. Facilitated diffusion
Passive diffusion
Molecules cross cell membrane through transport proteins

11. Active transport
Movement of substances from low to high concentrations
Against the concentration gradient
Requires energy

12. Types of active diffusion
Endocytosis: fluid, macromolecules, or other large particles brought into cell
Pouch forms in membrane lipids
Materials fill pouch
Pouch pinches in and breaks off from membrane
Now a vesicle
Two types:
Pinocytosis: transport of fluids
Phagocytosis: large particle transport
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13. Exocytosis Process by which a substance is released by a cell