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CELLS > ECM > Flashcards

ECM Flashcards

1
Q

What is the extra cellular matrix?

A

A complex network of proteins and carbohydrates that fill the spaces between cells

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2
Q

What type of components does the ECM consist of?

A

Fibrillar and non-fibrillar components

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3
Q

What does fibrillar mean?

A

Makes fibre

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4
Q

What are the two types of roles that the ECM plays in the cell?

A

an architectural role (influencing mechanical stability) and an instructional role (influences cell behaviour)

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5
Q

What three things is the ECM essential for?

A

Development, tissue function and organogenesis

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6
Q

What are they key functions of the ECM?

A
  1. Physical support
  2. Determines mechanical and physicochemical properties of tissue
  3. Influences the growth, adhesion and differentiation status of the cells and tissues
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7
Q

What type of tissue is particularly rich in extra cellular matrix?

A

Connective tissue

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8
Q

What are the three main components of the extra cellular matrix?

A

Collagens
Multi-adhesive glycoproteins
Proteoglycans

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9
Q

What is found in the basement membrane?

A

Type IV
Laminins
Perlecan

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10
Q

How can connective tissues have such varied properties?

A

the different types and arrangements of collagen, with the presence of different ECM components

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11
Q

What properties do connective tissues in the tendon and skin have?

A

Tough and flexible

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12
Q

What properties do connective tissues in bone have?

A

Hard and dense

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13
Q

What properties do connective tissues in the cartilage have?

A

Resilient and shock absorbing

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14
Q

What cell produces collagen

A

fibroblasts

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15
Q

What is connective tissue made up of?

A

Extracellular matrix and component cells

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16
Q

What are three proteoglycans?

A

Aggrecan, versican and decorin

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17
Q

What type of protein is collagen?

A

Fibrous

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18
Q

How many different collagen types exist in humans?

A

28

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19
Q

What structure does collagen form?

A

Triple helix

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20
Q

What is meant y a homotrimer?

A

When there is only one chain type

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21
Q

Which types of collagen are homotrimers?

A

Type II and III

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22
Q

What are the compositions of type II and type III collagen?

A

[a1(II)]3 and [a1(III)]3

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23
Q

What is meant by a heterotrimer?

A

When the chains arise from 2 genes

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24
Q

What type of collagen is a heterotrimer?

A

Type 1 Collagen

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25
Q

What is the composition of type 1 collagen?

A

[a1(I)]2 [a2(1)]

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26
Q

What is commonly the x and y in the glycine-x-y-repeat?

A 
X = proline
Y = hydroxyproline
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27
Q

Which amino acid occupies every third position in collagen proteins?

A

Glycine

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28
Q

why is glycine heavily involved in the structure of collagen?

A

Glycine is the only amino acid which is small enough to occupy the interior of the chain

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29
Q

What provides tensile strength and stability in collagen?

A

Intermolecular and intramolecular cross links

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30
Q

When does cross linking in collagen take place?

A

Only after the collagen has been secreted

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31
Q

What is an essential post- translational modification which contributes to interchain hydrogen bond formation?

A

The hydroxylation of proline and lysine

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32
Q

What enzymes are needed for the hydroxylation of proline and lysine?

A

Prolyl hydroxylase and Lysyl hydroxylase

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33
Q

What do Prolyl hydroxylase and Lysyl hydroxylase requires as a co-factor?

A

Vitamin C

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34
Q

What happens to collagen when you have vitamin C deficiency?

A

The collagen is underhydroxylated

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35
Q

When does the cross linking of collagen occur?

A

After the fibril formation

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36
Q

which collagens are fibril associated?

A

type 9 and 10

37
Q

What do fibril associated collagens do?

A

They regulate the organisation of collagen fibrils in the tissues

38
Q

What are the symptoms of Ehlers-Danlos syndrome?

A

Stretchy skin and loose joints due to mutations affecting collagen production in connective tissue

39
Q

How is the tensile strength of collegan established?

A

The fibres are held in parallel bundles which resist the tensile force in one direction

40
Q

What are collagen alpha chains synthesized from?

A

Longer precursors called pro-alpha chains

41
Q

what is cleaved from procollagen to make collagen?

A

N-terminal propetide and C-terminal propeptide

42
Q

Where is type 4 collagen found?

A

In all basement membranes

43
Q

What type of network does type 4 collagen form?

A

A sheet-like network

44
Q

What happens to the N and C terminus in type 4 collagen?

A

It remains intact

45
Q

What is another name for basement membranes?

A

Basal lamina

46
Q

What is the basement membrane?

A

A thin, flexible mat of extra-cellular matrix which the epithelial cell sheet sits on top of

47
Q

What structures are surrounded by basement membrane?

A

muscle, peripheral nerve and fat cells

48
Q

What do basement membranes form a part of the kidney?

A

They form a key part of the filtration unit as the glomerular basement membrane

49
Q

What is diabetes nephropathy?

A

Disorder where there is an accumulation of ECM leading to highly thickened basement membrane

50
Q

What is Alport Syndrome?

A

Where mutations in collage IV result in abnormally laminated Glomerular basement membrane which is associated with progressive loss of kidney function and hearing loss

51
Q

What helps to limit the extent of elastic fibres stretching?

A

The elastic fibres are interwoven with collagen

52
Q

What do elastic fibres consist of?

A

A core made up of elastin protein, surrounded by microfibrils which are rich in the protein fibrillin

53
Q

What amino acid side chains are covalently cross linked in elastin?

A

Lysine

54
Q

Describe the structure of elastin fibres

A

Elastin consists of two types of segments that alternate along the polypeptide chain: hydrophobic regions and a alpha-helical region that is rich in lysine and alanine - many of these lysin side chains are covalently crosslinked

55
Q

Where is fibrillin found?

A

In the microfibrils which surround the elastin core

56
Q

Mutations in fibrillin-1 are associated with what syndrome?

A

Marfans Syndrome

57
Q

What are patients with Marfans syndrome pre-disposed to?

A

Aortic ruptures

58
Q

How are ECM proteins able to multi-function?

A

They have a modular structure

59
Q

What is meant by multi-adhesive modular proteins?

A

The proteins can bind various matrix components and cell-surface receptors

60
Q

What is the shape of the laminin molecule?

A

A cross shape due to the presence of three chains - alpha, beta and gamma

61
Q

Are laminins large or small proteins?

A

Large

62
Q

Which surface cell receptors can laminins interact with?

A

Integrins and dystroglycans

63
Q

What mutation of laminin results in muscular dystrophy?

A

absence of the alpha 2 chain in laminin 2

64
Q

What are some symptoms of congenital muscular dystrophy?

A

hypotonia, generalised muscle weakness and deformities of the joint

65
Q

What are the two forms which fibronectins can exist as?

A

Insoluble fibrillar matrix or a soluble plasma protein

66
Q

How are different forms of fibronectins formed?

A

Alternate splicing of mRNAs

67
Q

What do fibronectins do?

A

play an important role in regulating surface adhesion and migration in a variety of processes, notably embryogenesis and tissue repair

68
Q

What is a proteoglycan?

A

core proteins which are covalently bonded to one or more glycosaminoglycan chains

69
Q

What proteoglycan is considered small and leucine rich?

A

Decorin

70
Q

What is the name of a cell surface proteoglycan?

A

Syndecans

71
Q

What is a GAG chain?

A

Glycosaminoglycan chain

72
Q

What makes up a GAG chain?

A

Repeating disaccharide units with one of the two sugars being an amino sugar

73
Q

What is an amino sugar?

A

A sugar in which one of the hydroxyl group is replaced with a amine group

74
Q

What has to happen to the GAG chain in order for it to carry a high negative charge?

A

Has to be sulfated or carboxylated

75
Q

What effect does the high negative charge of the GAG chain result in?

A

it attracts clouds of cations, including Na+, which therefore pulls water into the ECM through osmosis and the presence of a concentration gradient

76
Q

why does cartilage have a high tensile strength?

A

Catilage has a ECM with alot of collagen and GAG chains trapped in the meshwork, so the balance of swelling pressure is negated by the tension in the collagen fibres

77
Q

What are the four groups of GAG chains?

A

Hyaluronan
Chondroitin sulfate
Heparan sulfate
Keratan sulfate

78
Q

How is hyaluronan produced?

A

It is spun out directly from an enzyme embedded in the plasma membrane

79
Q

How id hyaluronan distinct from other GAG chains?

A

It is simply a carbohydrate chain without a core protein

80
Q

Why can hyaluranan chains occupy large volumes?

A

Because it can undergo a very high degree of polymerisation, which creates very large molecules

81
Q

What is the role of hyaluronan in joints?

A

Protects the cartilaginous surfaces from damage

82
Q

What is a major constituent of the cartilage ECM?

A

Aggrecan

83
Q

Aggrecan is highly sulphated What effect does this have?

A

Increases their negative charge which attracts cations that are osmotically active - leads to large amounts of water being retained by the negatively charged environment

84
Q

what is osteoarthiritis?

A

an erosive disease resulting in excessive ECM degradation

85
Q

What is lost with osteoarthiritis?

A

The cushioning properties of cartilage over the end of bones

86
Q

What leads to a loss of aggrecan fragments to the synovial fluid?

A

The cleavage of aggrecan by aggrecanases and metalloproteinases - this increases with age

87
Q

How do fibrotic diseases arise?

A

They are as a result of excessive production of fibrous connective tissue

88
Q

How is aggrecan perfectly suited to resist compressive forces in cartilage matrix?

A

Under compressive load, water is given up but is regained once the load is reduced

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