1. Passive vs. Active Transport

2. Characteristics needed for transport
1. Size of the molecule
2. Chemical structure of the molecule
– Charge and shape
1. Concentration of the molecule
2. Role played by the molecule

3. Passive Transport
• Does not require energy (ATP)
• Molecules always move from an area of high
concentration to low concentration
• Movement goes along with the concentration
gradient

4. Passive Transport Examples
• Simple Diffusion
– Includes osmosis
– Small molecules
– Lipid soluble particles
– Examples
• Oxygen
• Carbon dioxide
• Water

5. Passive Transport Examples
• Facilitated Diffusion
– Assistance in crossing the membrane
• Bigger molecules
• Not lipid soluble particles
– Specific carrier proteins
• Help molecules cross the membrane
• Examples
– Glucose
– Other simple sugars

6. Facilitated Diffusion Diagram

7. Passive Transport
Simple Facilitated
Diffusion Diffusion
Facilitated Diffusion diffuses molecules faster than
simple diffusion.

8. Passive Transport Examples
• Ion Channels
– Specific channels allows ion cross the
membrane
– Open vs. Gated
– Examples
• Ions – Calcium (Ca2+), Chloride (Cl-),
Sodium (Na+), Potassium (K+)

9. Ion Channels

10. Active Transport
• Does require energy
• Molecules usually move from an area of low
concentration to high concentration
• Movement goes AGAINST the concentration
gradient

11. Active Transport Examples
• Cell membrane pump
– Sodium-potassium pump
– Carrier protein pump
– Carries ions against the concentration
gradient
– Must “change shape” to function

12. Sodium-potassium pump
• 3 Na+ are pumped outside the cell
• 2 K+ are pumped inside the cell
• Creates a net positive charge outside the cell
membrane
• Animation
( http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html )
• Needed for cell to function
– Nerve impulse

14. Bulk Transport
• Large molecules
– Too big to pass through the cell membrane
– Molecules will “break through” by forming a
vesicle by either taking a piece of the
membrane away or adding a piece back
onto the membrane

15. Bulk Transport
• Endocytosis
– Substances is allowed into the cell
– Phagocytosis
• Macromolecules, whole cells or organisms
• Solids
– Pinocytosis
• Fluids and solutes

16. Bulk Transport
• Exocytosis
– Substances leaving the cell
• Overall picture

17. Membrane Transport
Passive Transport
Active Transport
Simple Diffusion Facilitated Diffusion
Pumps
Water Protein channels
Cotransport
Non-polar molecules
Large Molecules
Certain Ions
Endocytosis Exocytosis
Pinocytosis Phagocytosis