1. Cell Transport

2. Types of Transport Across Cell Membrane
Passive Transport
Active Transport
Cell doesn’t need energy
Moving molecules from HIGH to LOW concentrations
Three types
Cell does use energy
Moving molecules from LOW to HIGH concentrations
Three types

3. Passive Transport
Passive transport—the movement of molecules across a cell membrane without energy input from the cell
High → Low Movement
Concentration gradient—the difference in the concentration of a substance from one location to another

4. Diffusion
Diffusion—the movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration
Random movement through the membrane
Goes with the concentration gradient (HIGH → LOW)
Example: gas exchange in lungs, gas exchange between cells and blood

5. Facilitated Diffusion
Facilitated diffusion—the diffusion of molecules across a membrane through transport proteins
Movement of charged particles and/or larger molecules
Uses channel or carrier proteins
Also moves with the concentration gradient
Example: movement of glucose in the cell

6. Osmosis
Osmosis—diffusion of water molecules across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration
Movement of water molecules only

7. Effect of Osmosis on Cells
Water moves across cell membrane freely thus cells can’t control this movement
Three conditions

8. Result: Water moves out of the cell and the cell shrinks
Hypertonic—the concentration of solute is higher outside the cell than inside the cell
Result: Water moves out of the cell and the cell shrinks
Isotonic—the concentration of solute outside the cell are equal to the concentration of solutes in the cell
Result: Water moves equally in both directions and the cell remains the same size
Hypotonic—the concentration of solute is lower outside the cell than inside the cell
Result: Water moves into the cell and the cell swells

10. Active transport
Low → High Movement
Active transport— movement of molecules across a membrane from a region of lower concentration to a region of higher concentration
Requires energy from the cell

11. Protein Pumps
A transport protein that moves ions across the membrane with the use of energy
Requires the protein to change shape
Example: Sodium-Potassium Pump

12. Endocytosis
Endocytosis—the process of taking liquids or fairly large molecules into a cell by engulfing them in a membrane
Using the energy cell membrane folds in around the molecule
Vesicle combines with lysosome
Two types:
Phagocytosis—“cell eating”
Pinocytosis—“cell drinking”
Example: white blood cells eating bacteria

13. Exocytosis
Exocytosis—the release of substances from the cell by the fusion of a vesicle with the membrane
Opposite of endocytosis
Cell changes shape using energy
Example: waste and hormones released from a cell

14. References
Most information from Biology, McDougal Littell (2008)