Session 9-Collagen

Question 1

What is the basic unit of collagen?

Answer 1

Tropocollagen

Question 2

Which AA is in every third position along each alpha chain?

Answer 2

Glycine

Question 3

How many alpha chains is collagen made from?

Answer 3

Three

Question 4

What are the characteristics of the triple helix that forms collagen? (4)

Answer 4

1. Made up of alpha chains but not an alpha helix
2. Non-extensible
3. Non-compressible
4. High tensile strength

Question 5

Why is glycine so abundant in collagen?

Answer 5

Glycine is the only AA with a small enough side chain to fit in the middle of the helix on the inside

Question 6

Each alpha chain has this repeat: (Gly-X-Y)n.

Which AA are usually found in the X and Y positions?

Answer 6

Proline or hydroxyproline (hydroxyproline is not part of the 20 AA, it is formed when Pro is hydroxylated)

Question 7

Which bonds are found between alpha chains and what do they do?

Answer 7

Hydrogen bonds stabilise the structure

Question 8

How many types of collagen are there?

Answer 8

28

Question 9

What is the 1) molecular formula of type I collagen and 2) what is its tissue distribution?

Answer 9

1) Alpha1 (I)2 alpha2 (I)
2) skin
Tendon/ligaments
Bone
90% of all body collagen

Question 10

What is the 1) molecular formula of type II collagen and 2) what is its tissue distribution?

Answer 10

1) alpha1(II)3
2) Cartilage
Intervertebral discs

Question 11

What is the 1) molecular formula of type III collagen and 2) what is its tissue distribution?

Answer 11

1) alpha1(III)3
2) foetal skin
Cardiovascular system

Question 12

What is the 1) molecular formula of type IV collagen and 2) what is its tissue distribution?

Answer 12

1) alpha1(IV)2 alpha2(IV)

2) basement membrane

Question 13

Why is tropocollagen secreted before final processing occurs?

Answer 13

Collagen is large so the cell would burst

Peptidases are only activated outside the cell

Question 14

What causes scurvy?

Answer 14

Weak tropocollagen triple helices due to less vitamin C in the diet so hydrogen bonds cannot form

Question 15

What does CHADPOGRL stand for?

Answer 15

Cleavage of signal peptides
Hydroxylation of proline and lysine
Addition of N-linked oligosaccharide and galactose (in ER)
Disulphide bridge formation 
Procollagen (sent to golgi)
O-linked glycosylation (in golgi)
Golgi-exocytosis as tropocollagen 
Removal of N/C terminal peptides (procollagen peptidase)
Lateral aggregation to form fibrils