Collagen Biosynthesis

Question 1

What is an example of costitutive secretion?

Answer 1

Collagen

Question 2

What is an example of regulated secretion?

Answer 2

Insulin

Question 3

What is Ehlers-Danlos syndrome caused by?

Answer 3

Mutation in collagen type V or lysyl oxidase deficiency

Question 4

What is the basic unit of collagen fibres?

Answer 4

Tropocollagen

Question 5

How long and wide is tropocollagen?

Answer 5

300nm long, 1.5nm diameter

Question 6

How many polypeptides makes up tropocollagen?

Answer 6

3 polypeptides (alpha chains) each 1000 amino acids long

Question 7

What amino acid is in every 3rd position along alpha chain of tropocollagen?

Answer 7

Glycine

Question 8

What type of helix is tropocollagen?

Answer 8

Right handed triple helix

Question 9

What are the features of the triple helix structure of collagen?

Answer 9

Non extensible, non compressible, high tensile strength

Question 10

Why is glycine in every 3rd position along the alpha chain?

Answer 10

It is the only amin acid with a side chain small enough to fit in the middle of the helix

Question 11

What are the most common motifs in the amino acid sequence of collagen?

Answer 11

Glycine-Proline-X

Glycine-X-Hydroxyproline

Question 12

What are present between alpha chains of collagen to stabilise its structure?

Answer 12

Hydrogen bonds

Question 13

What are the stages of collagen biosynthesis? (CHADPOGRL)

Answer 13

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

Question 14

What is required for the hydroxylation of proline and lysine in collagen biosynthesis?

Answer 14

Prolyl/lysyl hydroxylase and Vitamin C

Question 15

What is required for the removal of N/C terminal peptides in collagen biosynthesis?

Answer 15

Procollagen peptidase

Question 16

When is the molecule no longer known as preprocollagen?

Answer 16

When the signal peptides are cleaved

Question 17

When does it become procollagen?

Answer 17

After modifications in the ER and it is sent to the golgi

Question 18

Where does the addition of N linked oligosaccharides and galactose occur?

Answer 18

ER

Question 19

What does prolyl hydroxylase require?

Answer 19

Vitamin C and Fe2+ ions

Question 20

What does prolyl hydroxylase allow?

Answer 20

Increased hydrogen bonding to stabilise triple helix

Question 21

What is scurvy due to?

Answer 21

Lack of vitamin C - weak tropocollagen triple helices

Question 22

What does abnormal collagen not contain?

Answer 22

Hydroxyproline

Question 23

How many extra N terminal amino acids and C terminal amino acids do not form the triple helix?

Answer 23

150 extra N terminal and 250 extra C terminal amino acids

Question 24

What helps to form covalent cross links between tropocollagen molecules?

Answer 24

Lysyl oxidase

Question 25

What does lysyl oxidase require?

Answer 25

Vitamin B6 and Cu2+ ions