1. Cell transport: Diffusion and Osmosis
Biology 11

2. Vocab:
Solute =a substance that is dissolved in another substance, thus forming a solution. (ie. salt, sugar)
Solvent = a substance, usually a liquid, in which other substances are dissolved, thus forming a solution.
(ie. Water)

3. Types of Membranes: Permeable: allows all (or most) things to cross
Selectively (semi-permeable) membrane: allows some things to cross but not others (ie. water can cross but solutes like salt and sugar can NOT)
Impermeable membrane: does NOT allow anything to cross

4. Transport- Passive or Active
Passive transport: the movement of materials across a cell membrane without the expenditure of cell energy
Active transport: the use of cell energy to move materials across a cell membrane (against concentration gradient)

5. PASSIVE TRANSPORT From high to low concentration
Does not require energy from the cell
Includes:
Diffusion
Osmosis
Facilitated diffusion

6. ACTIVE TRANSPORT From low to high concentration
Requires energy from the cell
Active transport proteins
Endocytosis
Exocytosis

7. DIFFUSION
The NET movement of particles from an area of high concentration to an area of low concentration

8. What is a concentration gradient?
Concentration Gradient the difference in concentration of solutes in a given space
Diffusion happens when substances move “down” a concentration gradient (from high to low) until the concentration of the two areas becomes equal.

9. Dynamic Equilibrium
At dynamic equilibrium there is no NET movement of particles.
DYNAMIC implies movement
EQUILIBRIUM implies a balance
No longer a concentration gradient
Particles move equally in all directions

10. Dynamic Equilibrium
NOTE: At D.E. particles are still moving, its just that overall, they will remain “mixed” unless acted upon by another force. (So no “net” movement overall).

11. Diffusion Diffusion will always be from an area of
___________ concentration to an area of
____________ concentration.
It will continue until _______________
_______________ is reached.
HIGH
LOW
DYNAMIC
EQUILIBRIUM

12. Diffusion Animations http://www.youtube.com/watch?v=qBig2wevHhw

13. OSMOSIS
The diffusion of WATER across a semi-permeable membrane.

14. Osmosis Animations

15. What is the difference between diffusion and osmosis?
Osmosis is just a “special case of diffusion”. It is the diffusion of water across a selectively permeable membrane.
Diffusion is the NET movement of particles from an area of high concentration to an area of low concentration!”

16. ENDOCYTOSIS
Cells surround and takes in material from the environment forming a vesicle or vacuole.
Includes pinocytosis and phagocytosis

17. Pinocytosis: Water and dissolved substances are taken up by the cell
“cell drinking”

18. Phagocytosis:
Up take of large particles by cells

19. EXOCYTOSIS
Vesicles from the inside of the cell fuse with the plasma membrane and release material on the outside of a cell.