1. Passive Transport and Active Transport
Chapter 7 Section 3

2. Passive Transport
Movement of molecules across a cell membrane without the input of energy
2 Types of Passive Transport:
Diffusion
Osmosis

3. Key Terms to Know
Concentration: the mass of solute in a given volume of solution
Equilibrium: concentration of the solute is the same throughout the sytem
Selectively Permeable Membrane: membrane that allows some substances to pass through the membrane while others cannot

4. Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration
Driven by the molecules kinetic energy until equilibrium is reached
No Energy Needed!

5. Diffusion Molecules can diffuse across a cell membrane by:
Dissolving in the phospholipid bilayer
Passing through pores in the cell membrane

6. Osmosis
Diffusion of water through a selectively permeable membrane

8. Osmosis
Net direction of osmosis is determined by the solute concentrations on the two sides of the membrane
When solute concentrations outside and inside the cell are equal, the two solutions are isotonic (which means same strength

9. Osmosis
When the solute concentration is higher outside of the cell is higher than inside of the cell, it is hypertonic.
Water will flow out of the cell
When the solute concentration is higher inside of the cell than outside of the cell, it is hypotonic.
Water will flow into the cell

10. Osmosis

11. Osmosis Hypertonic and Hypotonic solutions can cause osmotic pressure
Osmotic pressure can cause serious problems-----cells may burst
Vacuoles in plants help to regulate this process
Humans do not have an organelle to regulate b/c they have so many cells to absorb water

12. Facilitated Diffusion
In facilitated diffusion, a molecule binds to a carrier protein on one side of the cell membrane
The carrier protein then changes its shape, allowing it to pass across the cell membrane and deposit the molecule inside or outside of the cell
Still does not require energy!!!!

13. Facilitate Diffusion

14. Active Transport
Molecules move across the cell membrane from an area of lower concentration to an area of higher concentration
Active transport REQUIRES energy!!!!
Most types of active transport is accomplished by using carrier proteins or cell membrane pumps
Two Types:
Endocytosis
Exocytosis

15. Endocytosis
Process of taking material into the cell by means of infoldings, or pockets, of the cell membrane
Endo=“Inside”
Breaks loose from the outer cell membrane to form a vesicle or vacuole in plants
Large molecules, clumps of food, and even whole cells can be taken in this way

16. Endocytosis Endocytosis includes:
1) Pinocytosis: Process of endocytosis where the vesicle includes fluid or solutes
2) Phagocytosis: Process of endocytosis where the vesicle contains large particles or cells

17. Endocytosis

18. Exocytosis
The membrane of the vesicle or vacuole fuses with the cell membrane, forcing the contents out of the cell
Exo=“Outside”
Removal of water by the contractile vacuole is an example

19. Exocytosis