Biochemistry of the ECM Flashcards

1
Q

What type of molecule s collagen

A

A protein

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2
Q

What is the structure of collagen

A

It has a triple helical structure.

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3
Q

How does a single collagen chain become the triple helix structure

A

Three single left handed collagen fibres twist together to create a right handed triple helix.

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4
Q

What are the two major amino acids which make up collagen

A

Glycine and proline

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5
Q

What is the general formula for the amino acid make-up of collagen

A

(Glyc-X-Y)n - every third amino acid is glycine, the other two tend to be prolines.

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6
Q

What type of proline tends to make up the amino acid chain of collagen alongside glyceine

A

3-hydroxyproline and 4-hydroxyproline.

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7
Q

Why are glycine and proline the amino acids making up collagen

A

Because these are small amino acids - there is only space for small amino acids and these allow tight packing.

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8
Q

Why is collagen nutritionally poor

A

Hydroxyproline is unstable and it is deficient in other amino acids.

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9
Q

What are the three chains that wind together to make a collagen molecule

A

The three chains can be identical or non-identical.

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10
Q

In which type of collagen are the chains non-identical

A

Type I

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11
Q

In which types of collagen are the chains identical

A

Type II, III and IV.

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12
Q

What are the three chains which make up type one collagen

A

2 alpha 1 chains and 1 alpha 2 chain.

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13
Q

Where is type I collagen found

A

Bone, tendon, skin, lung, cornea, arteries

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14
Q

Where is type II collagen found

A

Cartilage.

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15
Q

Where is type III collagen found

A

Skin, lung, uterus, arteries, ligaments.

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16
Q

Where is type IV collagen found

A

Basement membranes

17
Q

Towards which terminal do collagen chains associate

A

The C terminal

18
Q

What is required in order for individual collagen chains to wind together into a triple helix

A

Hydroxylation

19
Q

What is the process of the formation of a collagen fibril

A

Individual collagen chains associated at C termini. They then undergo hydroxylation and glycosylation and wind together to form a triple helix. The triple helix is extruded from the cell and the N and C termini are cleaved to form a tropocollagen molecule. Tropocollagen molecules are then cross-linked to form a collagen fibril.

20
Q

What kind of structure do elastin fibres form (like how collagen fibres form a triple helix)

A

A mesh

21
Q

What is the name of the structures which link three or four elastin chains together

A

Desmosines.

22
Q

What is the structure of elastin fibres

A

There is an elastin core surrounded by micro-fibrils.

23
Q

What is the relationship between elastin fibres and emphysema

A

Elastin can be degraded by extracellular proteinases released by neutrophils in the inflammatory response. This can lead to emphysema where alveolar walls are broken down.

24
Q

What is the role of alpha 1 antitrypsin

A

Alpha 1 antitrypsin has a role in inhibiting the extracellular proteinases released by neutrophils in the inflammatory response to prevent the degradation of elastin.

25
Q

What is the impact of mutation and cigarette chemicals (oxidants) on alpha-1 antitrypsin

A

Mutations and oxidants can prevent the action of alpha 1 antitrypsin meaning that the proteinases are free to degrade elastin.

26
Q

What is the structure of PGs in cartilage

A

PGs are made up of glycoaminoglycans. These are acidic, sulphated and negatively charged. The negative charges attract anions which bring water and this means PGs are very hydrated.

27
Q

What happens to proteoglycans when they are compressed

A

Water is extruded

28
Q

Mutations closer to which end of collagen fibrils have the greatest impact

A

Mutations closer to the C termini have greater impact because collagen molecules wind up from the C termini.

29
Q

What are the three components of bone

A
  • Organic component - mostly collagen type I
  • Inorganic salts
  • Water
30
Q

What is the inorganic component of bone

A

Hydroxyapitite

31
Q

What are the stages of bone deposition

A

First the collagen matrix is laid down. The inorganic hydroxyapatite is laid on top and mineralises.

32
Q

What are two causes of poor mineralisation of bone

A
  • Vitamin D deficiency

- Chronic metabolic acidaemia

33
Q

What are the three components of the crystal lattice of hydroxyapatite

A
  • OH-
  • Ca2+
  • PO4^3-
34
Q

What are three nutritional and genetic diseases of collagen synthesis

A
  • Vitamin C deficiency (scurvy)
  • Osteogenesis imperfecta (brittle bone disease)
  • Ehler’s Danlos Syndrome.
35
Q

What is the cause of collagen defect due to vitamin C deficiency

A

Reduced hydroxylation

36
Q

What is the cause of the collagen defect in osteogenesis imperfecta type I

A

Decreased type I collagen levels

37
Q

What is the cause of the collagen defect in osteogenesis imperfecta type II

A

Abnormal type I collagen.

38
Q

What is marfan syndrome

A

A connective tissue disorder. This is a mutation in the fibrillin 1 gene on chromosome 15.

39
Q

In marfan syndrome, levels of what increase?

A

TGF beta.