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POM 2 Cell biology > 2.10 ECM > Flashcards

2.10 ECM Flashcards

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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 three 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 collagen (non-fibrillar)
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 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 5 proteoglycans? (PADS V)

A

Perlecan
Aggrecan
Decorin
Syndecans 1-4
Versican

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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 by 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

Both have 1 chain type

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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 I Collagen

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25
Q

What is the composition of type I collagen?

A
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26
Q

What are commonly the amino acids 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 triple helix

This gives collagen a stiff triple helix structure

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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

Fe2+ and vitamin C

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34
Q

What happens to collagen when you have vitamin C deficiency? What is this called?

A

The collagen is underhydroxylated thus affecting tissue stability

This is called scurvy

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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

What are the steps to collagen synthesis in fibroblasts?

A
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37
Q

What collagens are non-fibrillar (fibril-associated)?

A

Type IV, IX, X

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38
Q

What do fibril associated (non-fibrillar) collagens do?

A

They regulate the organisation of fibrillar collagens in tissues

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39
Q

What are the symptoms and cause of Ehlers-Danlos syndrome?

A

Stretchy skin and loose joints (joint hypermobility)

Due to mutations affecting collagen production in connective tissue

40
Q

How is the tensile strength of collagen established?

A

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

41
Q

What are collagen alpha chains synthesized from?

A

Longer precursors called pro-alpha chains

42
Q

What is cleaved from procollagen to make collagen in the case of fibrillar collagens?

A

N-terminal propetide and C-terminal propeptide

43
Q

Where is type IV collagen found?

A

In all basement membranes

44
Q

What type of network does type IV collagen form?

A

A sheet-like network

45
Q

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

A

It remains intact as type IV is non-fibrillar

46
Q

What does uncleaved N and C termini allow type IV collagen to do?

A

Interact with other collagen molecules to form a network of collagen, acting as a basement membrane

47
Q

What is another name for basement membranes?

A

Basal lamina

48
Q

What is the basement membrane?

A

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

49
Q

What structures are surrounded by basement membrane?

A

Muscle, peripheral nerve and fat cells

50
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

51
Q

What is diabetes nephropathy?

A

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

This results in less renal filtration and can cause renal failure

52
Q

What is Alport Syndrome?

A

Where mutations in collage IV result in an abnormally laminated glomerular basement membrane

This is associated with progressive loss of kidney function and hearing loss

53
Q

What helps to limit the extent of elastic fibres stretching?

A

The elastic fibres are interwoven with collagen

54
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

55
Q

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

A

Lysine

56
Q

Describe the structure of elastin fibres

A

Elastin consists of two types of segments that alternate along the polypeptide chain:

Hydrophobic regions and an alpha-helical region that is rich in lysine and alanine – many of these lysin side chains are covalently crosslinked

57
Q

Where is fibrillin found?

A

In the microfibrils which surround the elastin core

58
Q

Mutations in fibrillin-1 are associated with what syndrome?

A

Marfans Syndrome

59
Q

What are patients with Marfans syndrome pre-disposed to and what symptoms do they have?

A

Predisposed to aortic ruptures
Long spiderlike fingers and long slender limbs

60
Q

How are ECM proteins able to multi-function?

A

They have a modular structure

61
Q

What is meant by multi-adhesive modular proteins?

A

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

62
Q

What is the shape of the laminin molecule?

A

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

63
Q

Are laminins large or small proteins?

A

Large

64
Q

Which surface cell receptors can laminins interact with?

A

Integrins and dystroglycans

65
Q

What structure can laminins self associate as part of?

A

Basement membrane matrix

66
Q

What other matrix components can laminins interact with?

A

Type IV collagen, nidogen, proteoglycans

67
Q

What mutation of laminin results in congenital muscular dystrophy?

A

Absence of the alpha-2 chain in laminin-2

68
Q

What are some symptoms of congenital muscular dystrophy?

A

Hypotonia (decreased muscle tension)
Generalised muscle weakness
Deformities of the joints

69
Q

What are the two forms which fibronectins can exist as?

A

Insoluble fibrillar matrix or soluble plasma proteins

70
Q

How are different forms of fibronectins formed?

A

Alternate splicing of mRNAs

71
Q

What do fibronectins do?

A

Regulate cell surface adhesion
Regulate migration in a variety of processes, notably embryogenesis
Tissue repair

72
Q

Explain the multi-domain structure of fibronectin

A

Several domains are linked by disulphide bonds
Several collagen and cell binding sites are present

73
Q

How is fibronectin involved in the binding of collagen fiber to actin filament?

A

Fibronectin binds a collagen fibre and the integrin receptor on the other side, providing linkage between the ECM and cytoskeleton

Adaptor protein binds to the other end of the integrin receptor, and an actin filament binds to the adaptor protein

74
Q

What is a proteoglycan?

A

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

75
Q

What proteoglycan is considered small and leucine rich?

A

Decorin

76
Q

What is the name of a cell surface proteoglycan?

A

Syndecans

77
Q

What is a GAG chain?

A

Glycosaminoglycan chain

78
Q

What makes up a GAG chain?

A

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

79
Q

What is an amino sugar?

A

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

80
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

81
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

82
Q

Why does cartilage have a high tensile strength?

A

Cartliage has ECM rich in collagen and glycosaminoglycan chains trapped in mesh

Thus the balance of swelling pressure is negated by the tension in the collagen fibres

83
Q

What are the four groups of GAG chains?

A

Hyaluronan
Chondroitin sulfate
Heparan sulfate
Keratan sulfate

84
Q

How is hyaluronan produced?

A

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

85
Q

How is hyaluronan distinct from other GAG chains?

A

It is simply a carbohydrate chain without a core protein and is unsulfated

86
Q

Why can hyaluranan chains occupy large volumes?

A

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

87
Q

What is the role of hyaluronan in the synovial fluid of joints?

A

Protects the cartilaginous surfaces from damage

88
Q

Where else is hyaluornan found apart from in the synovial fluid of joints?

A

Vitreous humour of the eye

89
Q

What is a major constituent of the cartilage ECM?

A

Aggrecan

90
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

91
Q

what is osteoarthiritis?

A

an erosive disease resulting in excessive ECM degradation

92
Q

What is lost with osteoarthiritis?

A

The cushioning properties of cartilage over the end of bones

93
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

94
Q

How do fibrotic diseases arise?

A

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

95
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

POM 2 Cell biology (15 decks)

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