Extracellular matrix II Flashcards
Why must collagen fibres be made outside of the cell?
They are longer than a cell
What is the collagen chain that is first synthesised called?
pro-alpha chain
What is at the end of the pro-alpha chain?
Pro-peptides
What is significant about the pro-peptides?
They dont form the triple helical region
What is the triple helical region made up of?
Gly-x-y repeats
What can the x be in the Gly-x-y repeats?
lysine or hydroxylysine
What can y be in the Gly-x-y repeat?
proline or hydroxyproline
What region of the protein does the gly-x-y region form?
The fibrous region
What do the pro-peptides allow the pro-collagen to remain?
Soluble, so it won’t be precipitated
How is the triple helical structure made?
Self assembly of the pro-alpha chains
Where does the self assembly of the pro-alpha chains into the triple helical structure occur?
The ER/Golgi compartment
What happens to the procollagen triple helix once it has been formed in the ER/Golgi?
It is packaged into a secretory vesicle
How is the procollagen triple helix released?
From the plasma membrane, via a secretory vesicle
What do the secretory vesicles (containing the triple helices) do before they release the triple helices?
Align with each other along the CSM
What is cleaved off the triple helices once the procollagen has left the cell?
Propeptides
What happens once the propeptides have been cleaved off of the procollagen?
The fibre begins to assemble
How does the orientation of the collagen fibre come about?
As a result of the lining up of the vesicles before the procollagen was released
How is the assembly of the collagen from the procollagen fibres stabilised?
Through lysine-hydroxylysine and proline-hydroxyproline linkages
Effects of elastin?
Provides elasticity to tissues and cushions against pressure
What are the elastic fibres cross-linked by?
Lysine-hydroxylysine interactions
What is more flexible, elastins or collagen?
Elastins
How are elastins integrity maintained even when they are being stretched?
The single elastin molecules are cross-linked
What happens when the tension on an elastin fibre is released?
They go back to being more compact
What is a similarity between the ECM matrix of plants and animals?
They both mostly consist of polysaccharides
What polysaccharide is present in the matrix of a plant ECM?
pectin
Which polysaccharides are present in the matrix of animal ECM?
Glycosaminoglycans
Which glycosaminoglycans are present in animal ECM matrixes?
hyaluronan, chondroitin sulphate and heparan sulphate
What does not hyaluronan do that most other animal-ECM-matrix containing glycosaminoglycans do?
Form cross-links to proteins
What can chondroitin sulphate and heparan sulphate do that hyaluronan cant?
Form cross-links to proteins
What charge do glycosaminoglycans have?
Very negative
Glycosaminoglycans relationship with water?
hydrophilic
