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D1 Fall - Biochem > 11/6: Collagen Structure and Function I > Flashcards

11/6: Collagen Structure and Function I Flashcards

1
Q

Tissues not made up only of ________

A

Cells

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2
Q

What is the extracellular space filled with?

A

Network of large macromolecules (extracellular matrix)

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3
Q

What is composed from large reprtioire of proteins with various properties assembled into an organized network/meshwork, in close asociation with producer cells?

A

Extracellular matrix

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4
Q

What are specialized tissues in which ECM is more abundant than cells?

A

Connective tissues

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5
Q

What is the ECM critical in?

A

Many oral and craniofacial tissues:
Teeth/bone
Cartilage
Lamina propria beneath oral epithelium
Gingiva, periodontium

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6
Q

What tissue is made of specialized mineralized CT?

A

Teeth/bone

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7
Q

What tissue is made of proteoglycan-rich specialized CT?

A

Cartilage

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8
Q

What tissue is composed of collagen fibers in a connective tissue or STROMAL matrix (similar to dermis of skin)

A

Lamina propria beneath oral epithelium

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9
Q

What tissue is composed of a stromal matrix containing collagen?

A

Gingiva, periodontium

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10
Q

What are the cells embedded in the matrix?

A

Stroma

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11
Q

What are the major components of the stromal matrix?

A

Collagen embedded in polysaccharide ground substance of hyaluronan and proteoglycans/glyosaminoglycans

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12
Q

What are stroma cells derived from?

A

Mesodermal lineage

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13
Q

What do fibroblasts secrete?

A

ECM in most connective tissues

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14
Q

In specialized tissues, what is ECM secreted by?

A

Other fibroblast-related cells (osteoblasts, chondrocytes, odontoblasts)

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15
Q

What is a specialized matrix at interface between CT stroma and epithelium?

A

Basal lamina (separates them/anchors them)

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16
Q

What is the basal lamina tethered to underlying CT by?

A

Type VII collagen anchoring dibrils (“basement mebrane” - refers to basal lamina combined with this layer of collagen fibrils)

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17
Q

What is important in cell polarity?

A

Basal lamina

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18
Q

What makes up the major proportion of the tissue?

A

Extracellular matrix

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19
Q

What is the ECM traditionally viewed as?

A

Structurally stable material with function to provide support/anchorage to cells and tissues/damarcate boundaries between cells/tissues

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20
Q

What is the function of the ECM in bone?

A

Support and locomotion
Calcium homeostasis
Skeleton protects brain, internal organs

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21
Q

What is the function of the ECM in teeth?

A

Provides strength/structure to bone
Resists shear and compression forces associated with chewing

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22
Q

What is the function of the ECM in cartilage?

A

Support and locomotion
Resilient - shock absorber for compressive forces associated with locomotion/mastication

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23
Q

What is the function of the ECM in addition to structural roles?

A

Embryonic development (cell adhesion/migration/tissue morphogenesis)
Regulation of cell function (Signaling/growth/differentiation)
Tissue repair/wound healing
Angiogenesis

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24
Q

What can the ECM be viewed as?

A

Composite material
(various building materials w/ different mechanical properties combined/organized to create a tissue with optimal mechanical properties)

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25
Q

What are examples of diverse types of ECM?

A

Bone/teeth - calcified, hard ECM
Cornea - optically transparent ECM
Tendon - rope-like organization of collagen gives tensile strength in one direction

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26
Q

The ECM component of collagen provides what property?

A

Tensile strength

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27
Q

The ECM component of proteoglycans provide what property?

A

Resilience/resistance to compression

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28
Q

The ECM component of elastic provide what property?

A

Elasticity/resilience

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29
Q

The ECM component of fibrillin-1 (microfibrils) provides what property?

A

Controlled elasticity

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30
Q

The ECM component of mineral (hydroxyapatite) provides what property?

A

Strength, hardness, but also brittleness

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31
Q

Fibrous proteins are:

A
  1. Structural (collagen, elastin, fibrillins - provide tensile strength, elasticity)
  2. Adhesive (fibronectin, vitronectin, laminin - help cells attach to ECM)
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32
Q

What are long polysaccharides consisting of repeating
dissaccharide units – often covalently linked to protein in
the form of proteoglycans?

A

Glycosaminoglycans

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33
Q

What is the major structural component of ECM?

A

Collagens

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34
Q

What are Trimeric molecules consisting of three identical (homotrimeric) or non-
identical (heterotrimeric) polypeptide chains?

A

Alpha-chains

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35
Q

What are collagen molecules characterized by?

A

long, stiff triple stranded helical structure with 3 α-chains wound around each other in a rope-like
superhelix

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36
Q

What do all collagen molecules contain?

A

At least one triple helical region (collagenous domain)

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37
Q

What is collagen divided into?

A

Fibrillar
Non-fibrillar

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38
Q

What do fibrillar collagens assemble into?

A

Rod-like structures = collagen fibrils

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39
Q

What are the major fibrillar collagens?

A

I, II, III

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40
Q

What happens after fibrils form?

A

They are crosslinked between lysines of adjacent molecules

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41
Q

What is type I collagen?

A

Collagen found in tendon, bone, ligaments, dentin, skin

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42
Q

What is type II collagen?

A

Principle collagen in cartilage matrix

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43
Q

What chains encode type I collagen?

A

Heterotrimer of two alpha1 chains and one alpha2 chain

44
Q

What genes encode type I collagen?

A

COL1A1
COL1A2

45
Q

What do mutations in type I collagen genes associate with?

A

Osteogenesis imperfecta

46
Q

How are collagen fibrils arranged?

A

3D arrays
- parallel bundles
- orthogonal lattices
- concentric weaves
- wickerwork pattern
- fibrils in a swirling pattern

47
Q

What are type II collagen chains?

A

homotrimer of alpha1 chains

48
Q

What is type II collagen encoded by?

A

COL2A1

49
Q

What do mutations in type II collagen cause?

A

Chondrodysplasias

50
Q

What are examples of non-fibrillar collagen?

A

Type IV and VI
Type VII

51
Q

What type of collagen is an important role in basal lamina?

A

Type IV and VI

52
Q

What type of collagen is a key component of anchoring fibrils that attach epithelia to underlying connective tissue?

A

Type VII

53
Q

In collagenous domains, where is glycine present?

A

Every 3rd residue
X is often proline and Y is 4-hydroxyproline

54
Q

How does each collagen helix get stabilized?

A

By static repulsion of pyrrolidone rings of proline and hydroxyproline residues

55
Q

How do right handed triple helixes occur?

A

Three helical alpha-chains wind around each other

56
Q

For each Gly-X-Y, what forms between the amide hydrogen of a glycine in one chain and carbonyl oxygen of residue X in adjacent chain?

A

Hydrogen bond

57
Q

Where does hydrogen bonding occur?

A

Between OH groups and amide groups of residues in adjacent chains

58
Q

What position does glycine occupy?

A

3rd position - least bulky side chain, lets three alpha helix chains pack together to form a triple helix

59
Q

What are pos translational modifications of collagen important in?

A

Biosynthesis and assembly

60
Q

What does collagen undergo prior to triple helix formation?

A

Extensive post translational modifications

61
Q

What assist in correct trimerization and folding?

A

Several enzymes/molecular chaperones

62
Q

What do prolyl hydroxylases and lysyl hodroxylases do?

A

Hydroxylates prolines and lysines - requires vitamin C as cofactor

63
Q

What does FKBP10 do?

A

Accelerates protein folding

64
Q

What does collagen glycosyltransferase do?

A

Glycosylates selected hydroxylysines

65
Q

What does protein disulphide isomerase (PDI) do?

A

Catalyzes formation of interchain disulphide bonds between cysteins during nucleation of 3 polypeptide chains at c-terminus

66
Q

What does Hsp47 do?

A

Binds to disulfide bonded collagen trimers and helps complete formation of the triple helix

67
Q

What is important for fibril formation?

A

Proteolytic processing of procollagen molecules

68
Q

What is important
in nucleation of three
collagen chains to form a
collagen trimer?

A

C-propeptides

69
Q

When does fibril formation only occur?

A

After C and N propeptides are removed to form tropocollagen

70
Q

What do BMP-1/tolloid proteinaes do?

A

Cleave off c-propeptide

71
Q

What do ADAMTS2,3,14 do?

A

Cleave off n-propeptide

72
Q

What stabilizes the collagen fibrils?

A

Collagen crosslinking

73
Q

What are key enzymes in crosslinking?

A

Lysyl oxidases

74
Q

What occurs with inhibition of crosslinking?

A

Reduced tensile strength of fibrils/increases tissue dragility

75
Q

When does the amount of crosslinking increase?

A

With aging

76
Q

What is the only calcified tissue that doesn’t contain abundant collagen?

A

Enamel

77
Q

What attaches cementum layer of tooth root to alveolar bone?

A

Collagen in periodontal ligament

78
Q

What contains abundant collagen fibers to attach gingiva to tooth and alveolar bone?

A

Gingiva

79
Q

What are functions of collagen fibers in the gingiva?

A

− Anchoring gingival tissue to tooth/
alveolar bone
− Resisting masticatory forces

80
Q

What are the five groups that collagen fibers are classified into?

A

Dentinogingival
Alveogingival
Circumferential
Periosteal
Transseptal

81
Q

What is calcified into cementum/bone at one end,
free at other end?

A

Dentinogingival/alveogingival

82
Q

What is the function of dentinogingival/alveogingival fiber?

A

Hold free gingiva against tooth

83
Q

What fiber encirlces the tooth?

A

Circumferential

84
Q

What fiber holds attached gingiva against bone?

A

Periosteal

85
Q

What fiber runs between teeth?

A

Transseptal

86
Q

What collagen makes up the periodontal ligament?

A

Type I collagen

87
Q

What fibers are contained inside periodontal ligament?

A

Oxytalan fibers composed of fibrillin

88
Q

What are portions of fibrils anchored into mineralized cementum or bone?

A

Sharpey’s fibers

89
Q

What collagen restricted to narrow zone at the DEJ?

A

Type IV

90
Q

What collagen found in enamel organic matrix adjacent to DEJ?

A

Type VII
- fibers surround enamel rods

91
Q

What fiber may play a role in attachment of enamel to underlying dentin?

A

Type VII

92
Q

What collagen is important in basal lamina?

A

Type IV

93
Q

What is the basal lamina important for in kidney glomerulus?

A

determining which
molecules will pass into urine from blood (glomerular filtration)

94
Q

What is the basal lamina important for in skin?

A

Attaching epidermis (epithelial outer layer) to dermis

95
Q

What is the basal lamina important for in oral mucosa?

A

Attaching epithelium to
lamina propria

96
Q

What are other roles in addition to structural/filtration?

A
  • Determining cell polarity
  • Influencing cell metabolism
  • Regulating cell survival, proliferation, migration, differentiation
97
Q

What are key components of the basal lamina?

A

Glycoproteins
Collagens
Proteoglyvans

98
Q

What are glycoproteins in the basal lamina?

A

Laminins (primary component/main organizer)
Nidogen

99
Q

What collagen provides tensile strength in the basal lamina?

A

Type IV collagen

100
Q

What are proteogylcans in the basal lamina?

A

Perlecan (proteoglycan)

101
Q

What genes encode type 4 collagen alpha chains?

A

COL4A1
COL4A2
COL4A3
COL4A4
COL4A5
COL4A6

102
Q

What 3 heterotrimers can be formed in the basal lamina?

A

alpha 1,1,2
alpha 3,4,5
alpha 5,5,6

103
Q

What forms anchoring fibrils?

A

Type VII collagen

104
Q

What interacts with type I collagen in stroma and type IV collagen/laminin in basal lamina?

A

Anchoring fibrils

105
Q

What does type VII collagen anchor?

A

epidermis to underlying dermis or epithelium to underlying stroma

106
Q

What occurs due to a mutation in COL7A1?

A

Dystrophic epidermis bullosa

107
Q

What results in very fragile skin/mucous membranes
that blister easily and can be sloughed off, problems with
lining of the oesophagus?

A

Dystrophic epidermis bullosa

D1 Fall - Biochem (29 decks)

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