Test 2 Extracellular matrix and integrins

Question 1

Describe the ECM

Answer 1

• Extracellular matrix
  
  • 3-D network of proteins and polysaccharides
  • Most abundant connective tissue

Question 2

Describe the basement membrane?

Answer 2

• Thin layer of ECM and fibrous proteins that anchor and support the epithelium
• Secreted by both epithelial and connective tissue cells
  
  • Ties epithelium to the connective tissue underneath.

Question 3

Collagen Structure

Answer 3

• Helix of 3 a-chains
  
  • Chains contain long stretches of Gly-X-Y amino acid repeats
    
    • Glycine is tiny
    • X = any amino acid but often proline because it is a ring structure.
    • Hydroxyl (OH) group added to many of prolines and lysines in collagen.

Question 4

Collagen Types 1 and 3

Answer 4

• Fibril forming
  
  • Form connective tissues of skin, bone, tendon, cartilage, and ligaments.
  • Cornea
  • Capsules around organs.

Question 5

Collagen type 4

Answer 5

• Networking
• Forms flexible sheet-like mesh mostly because of breaks in triple helical structure/
• Gly-x-y repeats but with some repeats and non-collaganous domains on the end.
• Important in molecular filtration
  
  • Kidney glomerulus

Question 6

Collagen Type 6 and 9

Answer 6

• Fibril association
• Bind collage 1 fibers together (6)
• Anchor collagen 2 fibers to matrix (9)

Question 7

Glycosaminoglycans (GAGs)

Answer 7

• Composed of highly extended, repeating disaccharide chains
  
  • One is either N-acetylgucosamine or N-galactosamine
  • Normally sulfated (makes them very negatively charged.
  • Negative charge attracts cations such as Na+ which causes water to be drawn into matrix.
    
    • Gives it a gel like consistancey
      
      • Cartilage in knee.

Question 8

Proteoglycans

Answer 8

• Regulate distribution of extracellular signaling molecules
• Modulate signaling events at cell surface.
• Serve as structural constituents of ECM
• Regulate movement of molecules between intracellular and extracellular compartments.
• Form molecular seive in kidneys.

Question 9

Fibroblast growth factor must bind to what?

Answer 9

Must bind to proteoglycans to activate.

Question 10

Fibronectin

Answer 10

Blood clotting

Wound healing

Platelet adhesion and aggregation

Question 11

LAminin?

Answer 11

Interacts with Collagen 4 and proteoglycans .

Cross shaped structure

Question 12

Matrix Metalloproteinases function?

Answer 12

Endopeptidases that degrade ECM proteins

Requires Zinc or Calcium to function.

Question 13

Integrins structure and function

Answer 13

• Structure:
  
  • Two subunits A and B
    
    • A = specificty of binding
    • B - Interacts with cytoskeleton
  • Binding requires Magnesium or Manganese.
• Function:
  
  • No enzymatic activity
  • Assembles signalling complexes
  • binds to internal protein (kinase) and changes conformation depending on signal.