1. Section 3.3 – Movements Through Cell Membranes
Passive Transport
Active Transport

2. The Concentration Gradient
High Concentration
No Energy Required
Osmosis, Diffusion.
Facilitated diffusion
The steeper the gradient
the faster it flows!
Passive Transport
Active Transport
Concentration Gradient
Requires Energy
Pumping
Pinocytosis and Pagocytosis
The steeper the gradient
the more energy needed!
Low Concentration

3. PASSIVE TRANSPORT No Energy is Required
From High to Low Concentration.
Examples (see next slides)

4. Diffusion Passive High Low – Concentration Gradient Equilibrium
Example: hemodialysis

5. Animation: How Diffusion Works

6. Facilitated Diffusion
Passive
High Low
Uses a carrier molecule in the cell membrane

7. Animation: How Facilitated Diffusion Works

8. Osmosis Passive High Low
Diffusion of water through a selectively-permeable membrane

9. Animation: How Osmosis Works

10. Filtration Forces molecules through membranes Occurs by sheer force
Example: blood pressure

12. Isotonic Solution Same water concentration as inside the cell
Water will move back and forth, but no net movement.

13. Hypertonic Solution MUCH (hyper) solute (low water)
More water inside the cell than outside
Net movement of water OUT of the cell
Cell shrinks!!

14. Hypotonic Solution LITTLE (hypo) solute (high water)
More water outside the cell than inside
Net movement of water INTO the cell
Cell swells!!

15. Cells in Hypotonic solutions
Water diffuses into cell and it swells

16. Animation: Hemolysis and Crenation of Red Blood Cells

18. ACTIVE TRANSPORT Low  High concentration
Against the concentration gradient
*Requires Cellular Energy (ATP)

19. Types of Active Transport
Low  High
Requires Cellular Energy (ATP)

20. Endocytosis - cell takes in large particles by engulfing them
Pinocytosis – “ cell drinking”
Phagocytosis – “cell eating”
Receptor-mediated endocytosis – cell membrane binds to molecules first before bringing them in

21. Exocytosis - cell releases large particles to the outside

22. Animation: Endocytosis and Exocytosis

23. Animation Lysosomes
Shows Phagocytosis

24. Sodium Potassium Pump - the cell pumps out 3 sodium ions and takes in 2 potassium ions.

25. Animation: How the Sodium Potassium Pump Works