The Golgi Apparatus Flashcards
What does an oxidising environment in the ER promote
Promotes disulfide (S-S) bond formation (between the side chains of cysteine residues)
These bonds don’t form in the cytosol
Disulfide bonds formed in the ER is important in the structure of secreted and cell surface proteins
How are soluble proteins folded in the ER
Fold in lumen of ER
Disulphide bond formation
Sometimes modified by N-linked glycosylation or GPI anchor addition
Where do proteins go after being folded in the ER
To the Golgi
What is the cis and trans face of the golgi
Cis face- nearer to ER (receiving end) (vesicles from ER attach to cis face)
Trans face- nearer to Plasma Membrane (exit end)- pinch off vesicle containing proteins (can become a lysosome or exit cell) -> is concave
What is meant by the structure of the Golgi having intrinsic directionality
Fused vesicular tubules with proteins and lipids from ER enter (pinch off ER regions)
Proteins and lipids exit to cell surface or other organelles
Backwards of forwards (dynamic)
Number of stacks varies on cell types
What is the role of the Golgi
Accepts proteins and lipids from ER
Post translational modifications happen here
Covalently modifies, labels, sorts and sends them off
Oligosaccharide modifications, further additions to N-linked glycosylation added to many proteins
How is the Golgi organised
Enzymes are compartmentalised in the Golgi cisternae
Enzyme complexes for further N and O linked modification
How is the cisternae specialised for its role (stages of modification in the cisternae of Golgi)
How is N-linked glycosylation modified further in the Golgi
Already added in the ER and then further modified in Golgi
If exposed to Golgi enzymes- made more complex
Can be extremely variable
What is N-linked glycosylation
N-linked glycosylation, is the attachment of an oligosaccharide, a carbohydrate consisting of several sugar molecules, sometimes also referred to as glycan, to a nitrogen atom
What is O-linked glycosylation
Sugars added to OH groups of SER or THR side chains
Glycosylation transferases add the sugar nucleotides
What are muffins
Core of proteins of most mucus’s are called muffins
Heavily O-linked glycosylated
This gives mucus its sliminess
What are the two models which describe how proteins move through the Golgi
Vesicular transport model
Cisternal maturation model
Why do some proteins go backwards through the golgi
ER resident proteins and membrane replenishment
PH dependent - the ER is neutral, the golgi is acidic
How do some proteins go backwards through the Golgi
Luminal proteins
Membrane proteins