Collagen Biosynthesis Flashcards

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1
Q

What is an example of costitutive secretion?

A

Collagen

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2
Q

What is an example of regulated secretion?

A

Insulin

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3
Q

What is Ehlers-Danlos syndrome caused by?

A

Mutation in collagen type V or lysyl oxidase deficiency

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4
Q

What is the basic unit of collagen fibres?

A

Tropocollagen

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5
Q

How long and wide is tropocollagen?

A

300nm long, 1.5nm diameter

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6
Q

How many polypeptides makes up tropocollagen?

A

3 polypeptides (alpha chains) each 1000 amino acids long

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7
Q

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

A

Glycine

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8
Q

What type of helix is tropocollagen?

A

Right handed triple helix

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9
Q

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

A

Non extensible, non compressible, high tensile strength

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10
Q

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

A

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

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11
Q

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

A

Glycine-Proline-X

Glycine-X-Hydroxyproline

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12
Q

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

A

Hydrogen bonds

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13
Q

What are the stages of collagen biosynthesis? (CHADPOGRL)

A
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
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14
Q

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

A

Prolyl/lysyl hydroxylase and Vitamin C

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15
Q

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

A

Procollagen peptidase

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16
Q

When is the molecule no longer known as preprocollagen?

A

When the signal peptides are cleaved

17
Q

When does it become procollagen?

A

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

18
Q

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

A

ER

19
Q

What does prolyl hydroxylase require?

A

Vitamin C and Fe2+ ions

20
Q

What does prolyl hydroxylase allow?

A

Increased hydrogen bonding to stabilise triple helix

21
Q

What is scurvy due to?

A

Lack of vitamin C - weak tropocollagen triple helices

22
Q

What does abnormal collagen not contain?

A

Hydroxyproline

23
Q

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

A

150 extra N terminal and 250 extra C terminal amino acids

24
Q

What helps to form covalent cross links between tropocollagen molecules?

A

Lysyl oxidase

25
Q

What does lysyl oxidase require?

A

Vitamin B6 and Cu2+ ions