1. Chapter 7.3
Passive Transport

2. Homeostasis
For cells this is the relatively constant internal physical and chemical conditions

3. Cell Boundaries
Cell Membrane- regulates what enters and leaves the cell.
Also called the lipid bilayer (2 layers of lipids)
Gives cell flexible structure

4. Cell Wall Cell Wall- only found in plants outside the cell membrane.
Provides support and function for cell.
Allows things to enter and leave the cell.

5. Membranes
Permeable membrane: substance is able to diffuse across a membrane.
Impermeable membrane: substance cannot pass across a membrane.
Selectively permeable membrane: some substances can pass through and some cannot.

6. Two types of Transport Passive Transport Active Transport
No energy is required
Active Transport
Uses energy for the transport

7. Passive Transport Three types of passive transport Diffusion Osmosis
Facilitated Diffusion

8. Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration
Molecules will move “down” the concentration gradient until they hit equilibrium
When the concentration of molecules is equal through the space
Molecules do continue to move even in equilibrium

9. Lets look at an example

10. Factors that effect diffusion
Concentration gradient
Size of molecules
Types of molecules
Polar
Non polar
Chemical nature of the membrane

11. Osmosis Process by which water molecules diffuse across a membrane
Still moves high to low
Direction of movement depends on concentration

12. Concentration of Solvent
Hypotonic
Low solutes and high solvents
Hypertonic
High solutes and low solvents
Isotonic
Solutes and solvents are equal

13. How Cells Deal with Osmosis
Unicellular Organisms
Contractile vacuoles maintains equilibrium
Plant Cells
Turgor Pressure
Water fills the vacuole to maximum (plant)
Plasmolysis
Cell shrinks in hypertonic solution (plant/animal)
Cytolysis
Cell bursts in hypotonic solution (plant/animal)

14. Animal Cell

15. Plant Cell

16. Facilitated Diffusion
Movement of specific molecules from higher concentration to lower concentration by a protein channel
Carrier proteins are specific to each molecule

17. Diffusion through ion channels (passive)
Ions are not soluble across membrane
Specific to their ion
Factors the affect opening
Stretching of membrane
Electrical stimuli
Chemical signaling