Active Transport
Active Transport
Unlike passive transport, active transport requires
energy
– movement is against the concentration gradient
(from low to high)
– Energy required is cellular energy, aka ATP
2 methods of Active Transport
1. Via membrane proteins (pumps)
2. Change in the cell membrane (endocytosis, exocytosis)
Active Transport Pumps:
• Requires a membrane protein called a “pump”
• Pump directly uses ATP to transport substances
against concentration gradient.
Active Transport Pumps:
• Active transport pumps are specific to the
substance it transports.
• Like “lock and key”
Examples of active transport pumps:
– Proton pump transports hydrogen ions
Examples of active transport pumps:
• Sodium (Na+) / Potassium (K+) Pump
– 3 Na+ pumped out
– 2 K+ pumped in
http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html
Why are pumps necessary?
• Nerve cells need a difference in ions (charge)
on either side of the membrane so they can
fire.
• Which side of the cell membrane will have a
more “+” charge???
2 K+ in
3 Na+ out
Change in cell membrane
(2nd type of active transport process)
• Cell membrane will change its shape to
take in or release larger substances that
cannot pass through membrane proteins
• Involves vesicles
• Endocytosis moving materials into cell
• Exocytosis  moving materials out of
cell
Endocytosis “in”
– Takes in (engulfs) larger substances that
cannot pass through membrane proteins
– Cell membrane folds in until it forms a
vesicle
– There are two types of endocyotosis:
pinocytosis and phagocytosis
Phagocytosis:
• “Cell Eating”
– Pseudopods engulf
material with extensions
of the cell membrane.
– Ex. White blood cell taking
in foreign material for
destruction.
Phagocytosis:
Pinocytosis:
• “Cell Drinking”
– Membrane sips in
substance and pinches
membrane off into a
vesicle.
Pinocytosis:
Exocytosis: (OUT)
• Vesicle fuses with cell membrane, releasing
contents to outside of cell.
– ex. Waste
– ex. Digestive enzymes
Exocytosis: (OUT)
RNA
Rough ER
Golgi apparatus
Protein in vesicle
Plasma membrane
Figure 7.14 The formation and functions of lysosomes (Layer 1)
Figure 7.14 The formation and functions of lysosomes (Layer 2)
Figure 7.14 The formation and functions of lysosomes (Layer 3)