Extracellular matrix II

Question 1

Why must collagen fibres be made outside of the cell?

Answer 1

They are longer than a cell

Question 2

What is the collagen chain that is first synthesised called?

Answer 2

pro-alpha chain

Question 3

What is at the end of the pro-alpha chain?

Answer 3

Pro-peptides

Question 4

What is significant about the pro-peptides?

Answer 4

They dont form the triple helical region

Question 5

What is the triple helical region made up of?

Answer 5

Gly-x-y repeats

Question 6

What can the x be in the Gly-x-y repeats?

Answer 6

lysine or hydroxylysine

Question 7

What can y be in the Gly-x-y repeat?

Answer 7

proline or hydroxyproline

Question 8

What region of the protein does the gly-x-y region form?

Answer 8

The fibrous region

Question 9

What do the pro-peptides allow the pro-collagen to remain?

Answer 9

Soluble, so it won’t be precipitated

Question 10

How is the triple helical structure made?

Answer 10

Self assembly of the pro-alpha chains

Question 11

Where does the self assembly of the pro-alpha chains into the triple helical structure occur?

Answer 11

The ER/Golgi compartment

Question 12

What happens to the procollagen triple helix once it has been formed in the ER/Golgi?

Answer 12

It is packaged into a secretory vesicle

Question 13

How is the procollagen triple helix released?

Answer 13

From the plasma membrane, via a secretory vesicle

Question 14

What do the secretory vesicles (containing the triple helices) do before they release the triple helices?

Answer 14

Align with each other along the CSM

Question 15

What is cleaved off the triple helices once the procollagen has left the cell?

Answer 15

Propeptides

Question 16

What happens once the propeptides have been cleaved off of the procollagen?

Answer 16

The fibre begins to assemble

Question 17

How does the orientation of the collagen fibre come about?

Answer 17

As a result of the lining up of the vesicles before the procollagen was released

Question 18

How is the assembly of the collagen from the procollagen fibres stabilised?

Answer 18

Through lysine-hydroxylysine and proline-hydroxyproline linkages

Question 19

Effects of elastin?

Answer 19

Provides elasticity to tissues and cushions against pressure

Question 20

What are the elastic fibres cross-linked by?

Answer 20

Lysine-hydroxylysine interactions

Question 21

What is more flexible, elastins or collagen?

Answer 21

Elastins

Question 22

How are elastins integrity maintained even when they are being stretched?

Answer 22

The single elastin molecules are cross-linked

Question 23

What happens when the tension on an elastin fibre is released?

Answer 23

They go back to being more compact

Question 24

What is a similarity between the ECM matrix of plants and animals?

Answer 24

They both mostly consist of polysaccharides

Question 25

What polysaccharide is present in the matrix of a plant ECM?

Answer 25

pectin

Question 26

Which polysaccharides are present in the matrix of animal ECM?

Answer 26

Glycosaminoglycans

Question 27

Which glycosaminoglycans are present in animal ECM matrixes?

Answer 27

hyaluronan, chondroitin sulphate and heparan sulphate

Question 28

What does not hyaluronan do that most other animal-ECM-matrix containing glycosaminoglycans do?

Answer 28

Form cross-links to proteins

Question 29

What can chondroitin sulphate and heparan sulphate do that hyaluronan cant?

Answer 29

Form cross-links to proteins

Question 30

What charge do glycosaminoglycans have?

Answer 30

Very negative

Question 31

Glycosaminoglycans relationship with water?

Answer 31

hydrophilic