1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Movements Through Cell Membranes

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Selective Permeability  The plasma membrane allows some materials to pass while excluding others  This permeability includes movement into and out of the cell

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cellular Physiology: Membrane Transport  Membrane Transport – movement of substances into and out of the cell  Transport is by two basic methods  Passive transport  No energy is required  Active transport  The cell must provide metabolic energy

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Movement Through Cell Membrane  Passive Mechanisms of transport require no cellular energy  Ex:  Simple Diffusion  Facilitated Diffusion  Osmosis  Filtration

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport Processes  Diffusion  Molecules move from high concentration to low concentration, or down a concentration gradient  Equilibrium- Molecules tend to distribute themselves evenly within a solution DIFFUSION ANIMATION Figure 3.9 PRESS TO PLAY

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Diffusion through the Plasma Membrane Figure 3.10

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport Processes  Facilitated diffusion  Substances require a protein carrier (or Carrier Molecule) for passive transport  The rate of facilitated diffusion is limited to the number of carrier molecules in the membrane and/or the number of molecules available for transport.  Insulin promotes facilitated diffusion of glucose

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Facilitated Diffusion diffusion across a membrane with the help of a channel or carrier molecule glucose and amino acids

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport Processes  Osmosis –  simple diffusion of water from area of higher concentration to lower concentration

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Osmosis movement of water through a selectively permeable membrane from region of higher concentration to region of lower concentration water moves toward a higher concentration of solutes

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport  These are red blood cells in three different solutions:

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport  Hypertonic Solution  Has more solute particles (thus less H 2 O) than a cell in that solution  Result: Plasmolysis- cell shrinks

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport  Hypotonic Solution  Has less solute particles (thus more H 2 O) than a cell in that solution  Result: Cytolysis- cell bursts

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport  Isotonic Solution  Has the same concentration of solute particles as a cell in that solution  Result: Cell remains unchanged

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Passive Transport  Can you identify the solution each cell is in and explain what happens to each cell?

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes  Active Mechanisms require cellular energy (ATP)  Active Transport-  Particles move from an area of lower concentration to higher concentration  Up to 40% of cell’s energy supply is used for active transport

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes  Solute pumping  Amino acids, some sugars and ions are transported by solute pumps  ATP energizes protein carriers, and in most cases, moves substances against concentration gradients ACTIVE TRANSPORT ANIMATION PRESS TO PLAY

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes Figure 3.11

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes  Bulk transport  Endocytosis  A portion of the cell membrane forms vesicle to carry in particles too large for diffusion or pumping

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Endocytosis Figure 3.13a

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes  Types of endocytosis  Pinocytosis – cell drinking:  Portion of cell membrane becomes indented and surrounds tiny droplets of liquid. Membrane pinches off and carries liquid into cytoplasm where it releases contents  Phagocytosis – cell eating:  Solids are engulfed by indented portion of cell membrane which then pinches off and acts as vesicle to carry & empty solids into cytoplasm

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Active Transport Processes  Bulk transport  Exocytosis  Moves materials out of the cell  Material is carried in a membranous vesicle  Vesicle migrates to plasma membrane  Vesicle combines with plasma membrane  Material is released to the outside

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exocytosis Figure 3.12a