ECM

Question 1

Components of ECM

Answer 1

• Collagen
• Elastin
• non-collagenous glycoproteins
• Glycosaminoglycans
• Proteoglycans

Question 2

How is the EMC formed

Answer 2

Growth factors produced by cells in the tissues are what produces the features of the EMC

Question 3

How is the EMC degraded

Answer 3

Extracellular proteases secreted locally by cells:
- metalloproteases - Need Ca2+ and Zn2+
- Serine proteases - have serine at active site

Question 4

How is the EMC bound to by cells

Answer 4

Cell surface receptors (mainly integrins) interact with the cytoskeleton actin filaments and matrix glycoproteins.

Question 5

What are integrins

Answer 5

• Main EMC receptors
• Transmembrane glycoproteins in cell matrix junctions
• can activate intracellular signals
  composed of two non-covalently bonded sub-units

Question 6

What is collagen

Answer 6

• Gives tensile strength to tissue.
• Dense in glycine and proline and forms a triple helix structure.
• When exocytosis, ends of proto-collagen are cleaved so they can form crosslinks between fibres to form fibrils which wind into fibres

Question 7

What is elastin

Answer 7

Protein made of proline and glycine rich monomers. Cross linked by covalent bonds. Form loose helixes which can be stretched. Allowing out tissues to be stretchy.

Question 8

What is non-collagenous glycoproteins

Answer 8

• glycoproteins unrelated to collagen
  Involved in linking EMC and cells

Question 9

What are glycosaminoglycans (GAGs)

Answer 9

unbranched polysaccharide chains consisting of repeated disaccharide units

Question 10

What are proteoglycans

Answer 10

GAGs linked to proteins (Not hyaluronic acid)

Question 11

What are the 4 types of glycosaminoglycans

Answer 11

• Hyaluronic acid
• Chondroitin sulphate and dermatan sulphate
• Heparan sulphate and heparin
• Keratan Sulphate

Question 12

What is the EMC

Answer 12

3D scaffold surrounding cells consisting of protein fibres in a hydrated carbohydrate rich gel.

Question 13

What is the nature of disaccharide units in GAGs

Answer 13

amino sugars (often sulphated) + uronic acid
- The carboxylic and sulphur give a high negative charge - means highly hydrophilic

Question 14

What is an example of specialised EMC

Answer 14

Synovial fluid - contains lots of GAGs so good shock absorber since lots of water in EMC

Question 15

What are the cells that synthesise the EMC of connective tissue

Answer 15

Fibroblasts

Question 16

What are the cells that form EMC in cartilage

Answer 16

Chondroblasts

Question 17

What are the cells in the bone that form the EMC

Answer 17

osteoblasts

Question 18

What are co-receptors (syndecan)

Answer 18

Cell surface proteoglycans with membrane spanning core proteins

Question 19

Fibronectin - as an example of non-collagenous glycoproteins

Answer 19

• large glycoprotein made of two subunits bind by disulphide bonds
• integrin binding (cell surface)
• Heparin binding - other EMC proteins binding

Question 20

What can collagen binding to cell surface integrins trigger

Answer 20

triggers reorganisation of cytoskeleton and enables cell migration