1. CELLULAR TRANSPORT

2. THE CELL MEMBRANE
REMEMBER…The cell membrane controls the movement of substances into and out of the cell.

3. “COME ON AND TAKE A FREE RIDE” – PASSIVE TRANSPORT
No ATP (energy) needed
There are three types:
DIFFUSION
-Small molecules (CO2, H2O, O2, salts) can move between the phospholipid molecules of the bilayer.
-Molecules move from a HIGH concentration ([]) to a LOW [] along a CONCENTRATION GRADIENT until a balance is achieved.

4. Diffusion

5. Passive Transport 2. OSMOSIS
-The movement of water (from High to Low [ ]) through a selectively permeable membrane.

6. Osmotic Conditions Surrounding Cells
Isotonic solution – Solute [ ] outside of cell is equal to [ ] inside the cell. Cell remains normal.
Hypertonic solution – Fluid surrounding the cell has a higher solute [ ] than inside. Water diffuses out and the cell shrinks!
Hypotonic solution – [ ] of solute is higher inside the cell than outside. Water will diffuse into the cell. The cell expands!

7. Passive Transport
Osmosis is a VITAL fluid control process (blood and urine balance)

8. Passive Transport 3. FACILITATED DIFFUSION
-Some proteins in the cell membrane provide a “tunnel” for larger molecules (glucose) to diffuse through.
-They go with the concentration gradient!

9. ACTIVE TRANSPORT
ATP is the energy used to “pump” nutrients across cell membranes.
Using ATP, carrier proteins “pump” substances through a membrane from an area of LOW [ ] to an area of HIGH [ ] against the concentration gradient.
Eg. Page 74…the Na+/K+ pump in nerve cells

10. ACTIVE TRANSPORT

11. A QUESTION!
HOW DO THE REALLY LARGE MOLECULES (Hormones, polysaccharides etc.) move in and out of cells??

12. An Answer!! By two processes called ENDOCYTOSIS AND EXOCYTOSIS.
Both methods require the use of vesicles and ATP!

13. ENDOCYTOSIS –Moving materials into the cell
Three Types…
Phagocytosis
(Cell Eating):
-Used by white blood cells and amoeba.
-The cell moves out and surrounds the solid particle.

14. ENDOCYTOSIS –Moving materials into the cell
2. Pinocytosis (Cell drinking)
-Same process as phagocytosis except the cell
is moving liquids.

15. ENDOCYTOSIS –Moving materials into the cell
3. RME – Receptor Mediated Endocytosis
-Special receptor molecules on the membrane bind with the large molecule to be moved.
-When enough receptor molecules have gathered in one place, pinocytosis occurs.
-E.g. Moving cholesterol into the cell.

16. EXOCYTOSIS – Moving materials out of the cell
The reverse of pinocytosis
The vesicle (from the Golgi) fuses with the membrane and releases it’s contents out of the cell.
E.g. Hormones