The Golgi Complex, endoplasmic reticulum and vesicles
-Morphology consists of flattened, curved membrane disks arranged in an orderly stack
-Golgi stacks in mammalian cells are interconnected to form a large complex.
-Cis- (entrance) end of the organelle is referred to as the cis- Golgi network (CGN) where proteins to be
shipped back to the ER and those that proceed through the Golgi complex are sorted
-In the trans (exit) end of the organelle, the tubules and vesicles are known as the trans Golgi network
(TGN) where proteins are sorted into different types of vesicles heading to different destinations.
Glycosylation in the Golgi Complex: Golgi complex is very important in the assembly of carbohydrate
component of glycoproteins and glycolipids
-Golgi complex also the site of the synthesis of most of a cell's complex polysaccharides.
From the ER to the Golgi Complex:
-RER has exit sites without ribosomes
-Soon after vesicles bud from ER, they fuse with one another to form larger vesicles and connected
tubules in the region between ER and Golgi complex (ERGIC)
-Vesicular tubular carriers that form there are called VTC's.
Types of Vesicle Transport and their function:
-Vesicles are coated in protein to cause membrane to curve and form a budding vesicle, as well as
providing a mechanism for selecting components to enter vesicle
Types of Coated Vesicles:
1. COPII-coated vesicles: move materials from ER "forward" to ERGIC and Golgi complex
2. COPI-coated vesicles: move materials "backward; from ERGIC and Golgi towards ER or from trans
Golgi cisternae to cis Golgi cisternae
3. Clathrin-coated vesicles: move materials from TGN to endosomes, lysosomes and vacuoles in
plants. Move materials from plasma membrane to cytoplasmic compartments
-All have optimal activity at an acidic pH making them acid hydrolases
-High internal proton concentration to make acidic maintained by proton pump
-Best studied role is breakdown of materials from extra cellular environment
-Lysosomes ingest debris or bacteria which are then inactivated by the low pH of the lysosome
and digested enzymatically
-Peptides made from this digestive process are on cell surface to alert immune system to foreign
Plant Cell Vacuoles: