The Golgi Complex and the Endomembrane System Flashcards
(32 cards)
the golgi complex is closely related to the ER how?
in proximity and in function
what does the golgi complex consist of?
consists of a stack of flattened vesicles know as cisternae
functions of the golgi complex?
-plays an important role in processing and packaging secretory proteins, and in complex polysaccharide synthesis
what does the golgi accept?
vesicles that bud off the ER
- what happens to the contents of the vesicles from the ER after reaching the Golgi?
- what happens after that?
- they are modified and processed in the golgi complex
- the processed substances are then moved to other locations in the cell through vesicles that bud off the golgi complex
How is the golgi complex functionally and physically linked to the ER?
- glycoproteins and membrane lipids from the ER undergo further processing and are sorted and packaged for transport at the golgi
- golgi complex plays a central role in membrane and protein trafficking in euk cells.
The Golgi Commplex Consists of a Series of Membrane Bound Cisternae:
what is a golgi stack?
golgi stacks and cells?
- a golgi stack is a series of cisterna, usually 3-8
- some cells have one large stack, and other, especially secretory cells, have hundreds or thousands of stacks
Golgi complex and transport vesicles
- What do these transport vesicles surround? what do they do?
- the golgi complex lumen is part of the..?
- Both ER and the Golgi complex are surrounded by numerous transport vesicles that carry lipids and proteins from the ER to the Golgi complex and then to various destinations in the cell
- the golgi complex lumen (incisternal space) is part of the endomembrane system
Each golgi stack has two distinct..? called?
sides, or faces , called the cis and the trans faces
The cis face:
oriented towards?
golgi compartment on this side is called the?
- oriented towards the ER
- golgi compartment on this side is called the cis-golgi network (CGN)
The trans face:
which side?
golgi compartment called?
opposite side of the cis face
golgi compartment call the trans-golgi network (TGN)
The Golgi Network:
- proteins and lipids leave the golgi in?
- between the TGN and CGN are? what occurs here?
- what does each compartment contain?
- leave the golgi in transport vesicles that continuously bud off the tips of the TGN
- between TGN and CGN are medial cisternae, much of the processsing of proteins occurs here
- each compartment shows biochemical polarity, containing specific proteins unique to each portion of the network
Two Models Depict the Flow of Lipids and Proteins Through the Golgi Complex:
-similarities of models?
-what suggests that these models are not mutually exclusive?
what are the two models called?
- both models involve the formation of transport vesicles containing sorted cargo targeted for various destinations
- experimental evidence (tracking the movement of substances between the compartments and time-lapse fluorescent microscopy)
- the stationary cisternae model and the cisternal maturation model
Two Models Depict the Flow of Lipids and Proteins Through the Golgi Complex: The stationary cisternae model:
- what does is say about the cisternae?
- what is transport of materials done by?
- how does this happen?
- each cisternae in the golgi stack is a stable structure
- transport of materials from one cisternae to another is mediated by shuttle vesicles
- these bud off from one cisternae and fuse with the next cisternae in a cis- to trans- sequence
Two Models Depict the Flow of Lipids and Proteins Through the Golgi Complex: The cisternal maturation model:
- what does is say about cisternae?
- what happens to them?
- what happens to enzymes not needed in later compartments?
- golgi cisternae are transient compartments
- these gradually change from CGN through medial cisternae to TGN
- enzymes not needed in later compartments are returned to earlier compartments in vesicles
Anterograde and Retrograde Transport:
- what is anterograde transport?
- how does it work?
- this flow of lipids towards the plasma membrane must be?
- movement of material from the ER through the Golgi complex toward the plasma membrane
- every time a secretory granule fuses with the plasma membrane and discharges its contents by exocytosis, a bit of the membrane from the ER becomes part of the plasma membrane
- this flow of lipids towards the plasma membrane must be balanced (ie retrograde transport)
Anterograde and Retrograde Transport:
- what is retrograde transport?
- what does it allow?
- what does it ensure?
- the flow of vesicles from the golgi cisternae back to the ER
- cell recycles lipids and proteins no longer needed during the late stages of anterograde, which balances the flow of lipids towards the plasma membrane and ensures a supply of materials for forming new vesicles
Roles of the ER and Golgi in Protein Glycosylation:
- how is glycosylation related to the ER and Golgi?
- what is glycosylation
- what happens after glycosylation?
- protein processing carried out in the ER and golgi involves glycosylation
- the addtion of carbohydrate side chains to proteins to produce glycoproteins
- subsequent enzyme-catalyzed reactions then modify the oligosaccharide side chains that was attached to the protein
Roles of the ER and Golgi in Protein Glycosylation:
- what are the two general kinrds of glycosylation?
- N-linked glycosylation
- O-linked glycosylation
Roles of the ER and Golgi in Protein Glycosylation:
N-linked glycosylation:
-what is it?
-the addition of a specific oligosaccharide unit to the nitrogen atom on the terminal amino group of certain asparagine residues
Roles of the ER and Golgi in Protein Glycosylation:
O-linked glycosylation:
-what is it?
-the addition of an oligosaccharide to the oxygen atom on the hydroxyl group of certain serine or threanine residues
Roles of the ER and Golgi in Protein Glycosylation:
The initial steps of N-glycosylation
-where do the initial steps occur?
-where do later steps take palce?
-what do carbohydrate side chain initially have?
-first steps occur on the cytosolic surface of the ER membrane
-later steps take place in the ER lumen
-initially have a common core oligosaccharide:
>two units of N-acetylglycosamine
>nine mannose units
>three glucose units
Roles of the ER and Golgi in Protein Glycosylation:
Initial glycosylation occurs in the ER
-what are the steps? (6)
- glycosylation begins as dolichol phosphate, an oligosaccharide carrier, is inserted into the ER membrane
- GLcNAc and mannose groups are then added to the phosphate group
- the growing core oligosaccharide is translocated to the ER lumen by a flippase
- once inside the lumen, more mannose and glucose are added
- the completed core oligosaccharide is transferred from dolichol to the asparagine residue of the recipient protein
- the core oligosachharide is attached to the protein and is trimmed and modified.
Roles of the ER and Golgi in Protein Glycosylation:
Initial glycosylation occurs in the ER:
-what happens in cotranslational glycosylation?
-usually the oligosaccharide is added to the recipient protein as the polypeptide is being synthesized; promotes proper protein folding