ECM 1

Question 1

What is extracellular matrix?

Answer 1

Composed of a network of proteins and carbohydrates formed from leaving cells, with fibrillar and non-fibrillar proteins.

It surrounds connective tissue.

Question 2

What are the functions of extracellular matrix?

Answer 2

Physical support

Determines mechanical and physiochemical properties of the tissue

Essential for development, tissue function and organogenesis

Influences growth and adhesion of tissues with it interacts with

Question 3

What forms connective tissue?

Answer 3

ECM and component cells

• Collagens
  Type 1, 2, 3 - FIBRILLAR
  Type 4 - basement
  membrane
• Glycoproteins
  Fibronectin
  Fibrinogen
  Laminins - BM

- Proteoglycans
     Aggrecan
     Versican
     Decorin
     Perlecan - BM

Question 4

Which human disorders arise as a result of ECM abnormalities?

Answer 4

Gene mutations that affect matrix proteins

 - Osteogenesis Imperfecta - TYPE 1 COLLAGEN
 - Marfan's - FIBRILLIN 1
 - Epidermolysis Bullosa - LAMININ 5
 - Congenital Muscular Dystrophy - LAMININ 2

Gene mutations that affect ECM catabolism
- Hurler’s syndrome - L alpha iduronidase

Fibrotic disorders as a result of excess ECM deposition
- Liver fibrosis - CIRRHOSIS

Result of LOSS of ECm
- Osteoarthritis

Question 5

How does connective tissue vary?

Answer 5

Skin and tendon - flexible

Bone - hard

Cartilage - shock absorbing

Question 6

What is collagen? How many types are there?

Answer 6

Most abundant protein
Is fibrous, found in connective tissue

28 types of collagen, each with 3 chains - triple helix

• Type 1 - two i, one ii
• Type 2 - three i
• Type 3 - three ii

Question 7

What is the pattern of amino acid residue repeat in chains of collagen?

Answer 7

gly-x-y

Glycine is the 3rd AA due to its small size

Question 8

What is the organisation of collagen structure?

Answer 8

Triple chain - fibril - fibre

Question 9

How is collagen synthesised?

Answer 9

• Procollagen alpha chain synthesised
• Proline and lysine are hydroxylated
• N and C terminal pro-peptides are cleaved
• Fibril formed
• Crosslinking occurs - fibre formation

Question 10

Explain the process of lysine and proline hydroxylation and what conditions are required?

Answer 10

Form of post-translational modification

Allows for improved H bond cross-linkage

Uses hydroxylases requiring VIT C and Fe2+

Following this, covalen tcorss links form

Question 11

Which collagen is not fibrillar

Answer 11

Type 4 - forms networks in basement membranes

- sheet like network

Question 12

What are elastic fibres? What is the importance?

Answer 12

Core made of elastin, with microfibrils - have fibrillin

Provide elasticity of tissues

Question 13

What is Marfan’s syndrome?

Answer 13

Syndrome that leads to tall, slender patients due to a mutation of FIBRILLIN
1

Elastic fibres are overstretched

Question 14

What is elastin?

Answer 14

Protein with two regions

• hydrophobic
• alpha helical - can stretch

Question 15

What are basement membranes?

Answer 15

Aka basal laminae

Flexible thin layers of ECM under tissues

Act as filters for macromolecules