Session 10: Collagen

Question 1

Name the type of secretion collagen is secreted by

Answer 1

Constitutive (continuous regardless of external factors)

Question 2

What cell secretes collagen?

Answer 2

Fibroblast

Question 3

What is tropocollagen?

Answer 3

Basic unit of collagen

Question 4

Name three structural characteristics of tropocollagen.

Answer 4

1. 3 polypeptide alpha helix chains
2. Repetitive motif (Gly,X,Y)
3. Triple helix (right handed)

Question 5

Name three properties of a triple helix structure.

Answer 5

1. Non-extensible
2. Non-Compressible
3. High tensile strength

Question 6

What amino acid is usually in the X and Y positions? Why?

Answer 6

Proline/ hydroxyproline so H-bonds can form because of the presence of the -OH group

Question 7

What form of collagen is present BEFORE the protein enters the ER?

Answer 7

Pre-Procollagen (procollagen+Signal sequence to direct the protein to the ER)

Question 8

How is Procollagen modified in the ER?

Answer 8

1. Cleavage of signal peptide
2. Hydroxylation and glycolation
3. Disulphides bonds form between 3 alpha chains
4. Triple helix forms between N and C terminals

Question 9

What is scurvy a result of?

Answer 9

Weak tropocollagen triple helixs

Question 10

How is a collagen fibril formed?

Answer 10

Tropocollogen is secreted out of the cell and the C and N terminal removed by proteases. Basic units line up and cross links form.

Question 11

What is the name of the enzyme which form covalent cross links?

Answer 11

Lysyl Oxidase

Question 12

What is Ehlers-Danlos Syndrome (EDS) as a result of?

Answer 12

Lysyl Oxidase deficiency