1. Cell Transport
EQ: Explain how active and passive transport help the cell maintain homeostasis.
SC B-2.5
Explain how active, passive, and facilitated transport serve to maintain homeostasis of the cell

2. CELL TRANSPORT CHAPTER 7 SECTION 3
DEFINITIONS:
Equilibrium: state that exists when the concentration of a substance is the same throughout a space
Concentration Gradient: difference in the concentration of a substance across a distance

3. Passive Transport Diffusion Facilitated Diffusion Osmosis
dfn: movement of substances across a cell membrane without requiring energy expenditure by the cell
Types:
Diffusion
Facilitated Diffusion
Osmosis

4. Passive transport
Particles are said to move “down their concentration gradient”
It is free!

5. DIFFUSION
The movement of particles from regions of higher density to regions of lower density
Also called simple diffusion
Small, nonpolar molecules pass through the cell membrane by simple diffusion
Ex: oxygen, carbon dioxide

6. SIMPLE DIFFUSION

7. DIFFUSION RATE Rate of diffusion affected by: Temperature Surface area
Concentration gradient
Size of molecule

8. SIMPLE DIFFUSION ACROSS a MEMBRANE

9. FACILITATED DIFFUSION
Same as simple diffusion (particles move down their concentration gradient) except particles require the use of a transport protein to cross cell membrane

10. FACILITATED DIFFUSION
Because it requires a transport protein there is an upper limit to the # of molecules that can enter/exit a cell at any given moment
(called Tmax)

11. Facilitated Diffusion
Glucose enters cells via facilitated diffusion

12. OSMOSIS
Osmosis : the diffusion of water from a more dilute solution  a more concentrated solution through a membrane that is permeable to water but not to the solute solute: what is dissolved in solvent solvent: what dissolves the solute

13. Osmosis
Allows cells to maintain water balance as their environment changes

14. Osmosis In humans used by: Respiratory system Reproductive system
Water Channels (called aquapores) in membrane to allow polar water molecules to enter/exit cell
In humans used by:
Respiratory system
Reproductive system
Urinary system (water conservation)
Digestive system
Homeostasis of body temperature

15. Osmosis in Red Blood Cells
Hypertonic Solutions
Concentration of solutes higher than that in cytoplasm
Water follows its concentration gradient and moves from ______________ to ___________
Cells will _________________, called crenation

16. Osmosis in Red Blood Cells
If the solution is hypotonic, there is a lower solute concentration outside the cell than inside the cell
Water will move _____________
The cell will __________, called hemolysis.

17. Osmosis with Red Blood Cells
If the solution the red blood cell is in has the same concentration of water as the cytoplasm in the cell there will be _________ movement of water.
This is called an isotonic solution.

18. Osmosis in Plant Cells

19. PASSIVE TRANSPORT

20. ACTIVE TRANSPORT
Dfn: the movement of substances against their concentration gradient (against the flow)
Substances are moving from an area of lower concentration to an area of higher concentration
This requires the cell to use energy (ATP)

21. ACTIVE TRANSPORT
TWO TYPES:
PUMPS
VESICLES
ENDOCYTOSIS
EXOCYTOSIS

22. ACTIVE TRANSPORT PUMPS
Use a carrier protein (like facilitated diffusion) but requires expenditure of energy
Most common pump:
Na+/K+/ATP pump

23. Na+/K+/ATP pump
A carrier protein that uses ATP (1) to actively transport sodium ions (3) out of the cell and potassium ions (2) into the cell.
This pump keeps the [Na+] inside the cell lower so that osmosis will not cause the cell to swell with water.

24. ACTIVE TRANSPORT VESICLES
Used to transport molecules that are too large to fit thru a carrier protein.
Endocytosis
Cell “eating” (phagocytosis) or cell “drinking” (pinocytosis)
Cell wraps membrane around material forming vesicle which is taken into cell
Exocytosis
For moving material out of cell
Vesicle fuses with cell membrane releasing contents outside of cell

25. ENDOCYTOSIS
EXOCYTOSIS

26. Endocytosis Exocytosis

27. Active Transport Animation

28. Review Time