Rest of ECM

Question 1

What are basement membranes?

Answer 1

Flexible, thin mats of ECM underlying epithelial sheets and tubes

Question 2

Kidney example of BM

Answer 2

In the kidney they form part of the filtration unit Glomerular Basement Membrane (GBM)

Question 3

Elastic fibre structure?

Answer 3

Core of protein elastin and microfibrils which contain the protein fibrillin

Question 4

Marfan’s syndrome?

Answer 4

Mutations in protein fibrillin-1 leads to excessive elasticity, seen in Marfan’s syndrome

Question 5

Elastin structure?

Answer 5

Important for streching and relaxing, hydrophobic regions and a-helical regions in alanine and lysine alternate along the peptide chain

Question 6

3 characteristics of laminins?

Answer 6

• Heterortrimeric proteins made up of an alpha, beta and gamma chain
• Multi-adhesive so can interact with a variety of receptors, can self associate and interact with other matrix components
• Mutations linked to diseases like muscular dystrophy, epidermolysis bullosa and hypotonia

Question 7

3 characteristics of fibronectins?

Answer 7

• Can exist as insoluble fibrillar matrix or soluble plasma protein
• Interact with a variety of receptors
• Can form a mechanical continuum with actin cytoskeletons

Question 8

What are proteoglycans?

Answer 8

Core proteins covalently attached to one or more glycosaminoglycan (GAG) chains.

Question 9

GAG chains?

Answer 9

GAG chains are made up of repeating disaccharide units with one of the two sugars being an amino sugar. Many chains are sulfated or carboxylated and so are highly negatively charged. The charge attracts cations like Na+ so large amounts of water gets sucked into the ECM

Question 10

Cartilage?

Answer 10

Balance of swelling pressure of lots of collagen negated by tension in collagen fibres. Creates high tensile strength

Question 11

4 main groups according to the repeating disaccharide unit?

Answer 11

• Hyalunoronan (also called hyaluronic acid) is spun from an enzyme embedded in the plasma membrane
• Chondroitin sulfate and dermatan sulfate
• Heparan sulfate
• Keratan sulfate

Question 12

Hyaluronan?

Answer 12

• Different to other GAG’s as it is a carbohydrate chain
• Occupies a very large volume
  E.g vitreous humour

Question 13

Aggrecan?

Answer 13

• Major constituent of cartilage ECM
• Highly negative environment due to sulfated GAGs and carboxyl groups. The charge attracts Na+ ions which attracts water due to osmosis
• Under compressive load, water is given up and then regained. Aggrecan is suited to resist compressive forces

Question 14

2 diseases?

Answer 14

• Osteoarthritis due to excess ECM degredation

- Fibrotic diseases- excessive production of fibrous connective tissue