Collagen

Question 1

Describe the structure of collagen.

Answer 1

• right handed triple helix made of 3 a-chains
• each chain has a Gly-X-Y repeating seq
• basic subunit is tropocollagen
• triple helix is non-extensible, non-compressible and has high tensile strength
• strong structural protein

Question 2

Which cells synthesise collagen?

Answer 2

Fibroblasts

Question 3

Describe collagen synthesis.

Answer 3

1. Transcription of collagen gene in nucleus and co-translational transport of preprocollagen into ER
2. Formation of pro collagen a-chains by
   
   1. Vit C dep hydroxylation of selected Pro and Lys residues
   2. N-linked glycosylation
   3. S-S formation at C-terminal
3. This promotes assemble of pro collagen triple helix
4. O-linked glycosylation in Golgi
5. Packaged into secretory vesicles
6. N and C terminal propeptides are cleaved, leaving tropocollagen
7. Tropocollagen covalently binds to other tropocollagen, forming fibrils and collagen fibres

Question 4

What type of secretion does collagen show?

Answer 4

Constitutive

Question 5

List major types of collagen.

Answer 5

1. Type I - fibrillar, most abundant, bone
2. Type II - fibrillar, cartilage
3. Type III - fibrillar, extensive connective tissue
4. Type IV - network, basement membrane

Question 6

List some conditions asso w collagen defects.

Answer 6

1. Scurvy
2. Ehlers-Danlos syndrome
3. Alport syndrome
4. OI