Passive vs. Active Transport

Characteristics needed for transport

1. Size of the molecule

2. Chemical structure of the molecule– Charge and shape

3. Concentration of the molecule

4. Role played by the molecule

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

Passive Transport Examples

• Simple Diffusion– Includes osmosis– Small molecules– Lipid soluble particles– Examples

• Oxygen• Carbon dioxide• Water

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

Facilitated Diffusion Diagram

Passive Transport

Simple Diffusion

Facilitated Diffusion

Facilitated Diffusion diffuses molecules faster than simple diffusion.

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+)

Ion Channels

Active Transport

• Does require energy• Molecules usually move from an area of low

concentration to high concentration• Movement goes AGAINST the concentration

gradient

Active Transport Examples

• Cell membrane pump– Sodium-potassium pump– Carrier protein pump– Carries ions against the concentration

gradient– Must “change shape” to function

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

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

Bulk Transport

• Endocytosis– Substances is allowed into the cell– Phagocytosis

• Macromolecules, whole cells or organisms• Solids

– Pinocytosis• Fluids and solutes

Bulk Transport

• Exocytosis– Substances leaving the cell

• Overall picture

Membrane Transport

Active Transport

Protein channels

Certain Ions

Non-polar molecules

Water

Facilitated DiffusionSimple Diffusion

Passive Transport

Endocytosis

Pumps

Cotransport

Large Molecules

Pinocytosis Phagocytosis

Exocytosis