Chapter 12.2: The Endomembrane System

Exocytosis

Secretory vesicles release their contents outside the cell

Endocytosis

The process by which cells internalize external materials

Constitutive Secretion

After budding from TGN some vesicles move directly to the cell surface and immediately fuse with the plasma membrane

Regulated Secretion

Vesicles accumulate in the cell and only fuse with the membrane in response to specific signals

Polarized Secretion

Exocytosis of specific proteins is limited to a specific surface of the cell

Phagocytosis

Ingestion of large particles including cells and microorganisms(restriced to phagocutes in complex organisms)

Neutrophills and Microphages

Types of white blood cells that use phagocytosis as a means of defense

Why are phagocytes studied in Amoeba?

They use phagocytosis for nutrition

Receptor-Mediated Endocytosis

Use receptors on outer celll surface to internalize macromolecules

Receptor-Mediated Endocytosis(1)

Use receptors on outer cell surface to internalize macromolecules

Receptor-Mediated Endocytosis(2)

Receptor-ligand complexes diffuse laterally

Receptor-Mediated Endocytosis(3)

Adaptor proteins, clathrin and dynamin induce curvature and invagination of the pit

Receptor-Mediated Endocytosis(4)

Pit pinches off forming a coated vesicle

Receptor-Mediated Endocytosis(5)

Clathrin Coat is released; coat proteins, clathrin and dynamin, are released

Receptor-Mediated Endocytosis(6)

Uncoated vesicle fuses with early endosymes

Transocytosis

Process of moving material across one side of the membrane to the other

After Internilization

Uncoated vesicles fuse with vesicles budding from the TGN to form early endoscopes

Recyvling Plasma membrane receptors

The ph gradually declinse as the endosome matures facillitated by an ATP dependent proton pump; lower pH dissociates ligand and receptors allowing receptors to be returend to the membrane

Coated Vesicles

Have layers of proteins covering their Cytosolic surfaces

Clathrin Origin

TGN or Plasma Membrane

Clathrin Destination

Endosomes

COPI Origin

Golgi apparatus

COPI Destination

ER or Golgi apparatus

COPII Origin

ER

COPII destination

Golgi apparatus

Caveolin Origin

Plasma Membrane

Caveolin Destination

ER

Dynamin is a GTPase

True

V-Snares

SNAP receptor protein found on vesicles

T-Snares

SNAP receptor protein found on target membrane

RAB GTPase

once a vesicle reaches its target destination it locks the complementary snare proteins together facilitating membrane fusion

Where are Lysosomal enzmes synthesized

Rough ER ribosomes

Peroxisomes function

Hydrogen peroxide metabolism

Detoxification of harmful compounds

Oxidation of fatty acids

Metabolism of nitrogen-containing compounds

Catabolism of unusual substances