Understanding:
• Vesicles move materials within cells
Materials destined for secretion are transported around the cell in membranous containers called vesicles
Endoplasmic Reticulum
The endoplasmic reticulum is a membranous network that is responsible for synthesising secretory materials
- Rough ER is embedded with ribosomes and synthesises proteins destined for extracellular use
- Smooth ER is involved in lipid synthesis and also plays a role in carbohydrate metabolism
Materials are transported from the ER when the membrane bulges and then buds to create a vesicle surrounding the material
Golgi Apparatus
The vesicle is then transported to the Golgi apparatus and fuses to the internal (cis) face of the complex
- Materials move via vesicles from the internal cis face of the Golgi to the externally oriented trans face
- While within the Golgi apparatus, materials may be structurally modified (e.g. truncated, glycosylated, etc.)
Material sorted within the Golgi apparatus will either be secreted externally or may be transported to the lysosome
Plasma Membrane
Vesicles containing materials destined for extracellular use will be transported to the plasma membrane
The vesicle will fuse with the cell membrane and its materials will be expelled into the extracellular fluid
Materials sorted by the Golgi apparatus may be either:
- Released immediately into the extracellular fluid (constitutive secretion)
- Stored within an intracellular vesicle for a delayed release in response to a cellular signal (regulatory secretion)
Overview of Vesicular Transport
