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MCBM Exam 3 > ECM > Flashcards

ECM Flashcards

1
Q

Connective tissue has a high ratio of ___ to cells in connective tissue.

A

ECM

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2
Q

What function does the ECM play in connective tissue?

A

Structural - provides architectural framework

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3
Q

What determines the physical properties of the connective tissue?

A

Composition of the matrix

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4
Q

The ECM provides support for what?

A

Cells and cell layers

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5
Q

The ECM acts as a barrier to what?

A

Cells

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6
Q

The ECM acts as a passive-selective ___-___ between tissue compartments.

A

Molecular sieve

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7
Q

What acts as a solid phase regulator of cell attachment, growth and differentiation?

A

ECM

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8
Q

ECM modulates what process?

A

Mineralization process

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9
Q

What are the three structural components of ECM?

A

Fibers
Amorphous ground substance
Basement membrane

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10
Q

What is a filament?

A

A threadlike structure (2-20 nm dia.)

Typically a single molecule or linear chain of molecules

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11
Q

Microfibrils are an aggregate of what?

A

Filaments

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12
Q

What is the typical diameter of a microfibril?

A

45-100 nm diameter

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13
Q

What is an aggregate of microfibrils called?

A

A fibril

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14
Q

What is the diameter of a fibril?

A

200-500 nm diameter

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15
Q

What is an aggregate of fibrils called?

A

A fiber

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16
Q

How big are fibers?

A

1-20 micrometers in diameter

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17
Q

What are the two types of fibers in the ECM?

A

Collagen

Elastic

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18
Q

How big are bundles?

A

20-100 micrometers in diameter

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19
Q

What makes up ground substance?

A

A complex mixture of glycoproteins, gags and proteoglycans

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20
Q

Ground substance helps bind cells to what of connective tissues?

A

Fibers

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21
Q

Ground substance fills the space between what?

A

Cells and fibers in connective tissue

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22
Q

What is a glycoprotein?

A

A protein with one or more attached sugars

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23
Q

A GAG is a family of what?

A

Heteropolysaccharides

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24
Q

GAGs are very ___ and very ___ ___.

A

Hydrated

Negatively charged

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25
Q

What is a proteoglycan composed of?

A

Protein core with many GAG chains attached

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26
Q

What glycoproteins are found in interstitial connective tissue?

A 
Fibroconectins
Elastin
Fibrilins
Tenascins
Thrombospondins
Microfibril-associated matrilins
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27
Q

What glycoproteins are found in basement membranes?

A

Laminins
Nidogen/entactin
Fibulin

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28
Q

What are the small leucine-rich proteoglycans?

A 
Decorin
Biglycan
Fibromodulin
Lumican
Epiphycan
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29
Q

What are the modular proteoglycans involved in nonhyaluronan binding?

A

Prelecan
Agrin
Testican

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30
Q

What modular proteoglycans are involved in hyaluronan and lectin binding?

A

Aggrecan
Versican
Neurocan
Brevican

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31
Q

The large majority of the extracellular matrix is synthesized and secreted locally by what?

A

Neighboring cells

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32
Q

What makes most connective tissue?

A

Fibroblasts

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33
Q

What specialized CT cell makes dentin?

A

Odontoblasts

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34
Q

What specialized CT cells makes enamel?

A

Ameloblasts

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35
Q

Enamel is considered to be what?

A

Epithelial

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36
Q

What is the most abundant protein in the body?

A

Collagen

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37
Q

Collagen is about ___% of the protein in the body by weight

A

30%

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38
Q

The cornea is about ___% protein.

A

64%

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39
Q

What type of helix is collagen?

A

Left-handed

It is a specialized “collagen helix”, not a true alpha helix

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40
Q

What ring structure adds rigidity to collagen?

A

Proline

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41
Q

In mature form, collagen doesn’t have what two amino acids?

A

Cystein

Tryptophan

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42
Q

What is tropocollagen

A

3 helical strands of collagen wrapping around each other

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43
Q

How do tropocollagen fibrils arrange themselves?

A

In a staggered array of parallel bundles

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44
Q

What causes striations in collagen?

A

Alignment of every 4th molecule

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45
Q

What forms crosslinks in collagen?

A

Lysinonoreleucine

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46
Q

What enzyme does the production of lysinonorleucine require?

A

Lysyl amino oxidase

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47
Q

Lysyl amino oxidase requires which cofactor?

A

Vitamin B6 (pyridoxine)

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48
Q

What does each collagen molecule consist of?

A

Three alpha-chains

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49
Q

The collagen family has how many different alpha-chains?

A

34

50
Q

Fibrillar collagens form ___ fibers with ___ strength.

A

Long

Tensile

51
Q

Non-fibrillar collagens can partially organize into how many groups?

A

4

52
Q

What are the 4 types of non-fibrillar collagens?

A

Basement membrane collagens
Fibril-associated collagen with interrupted triple helix
Multiplexins
Microfibrillar collagen

53
Q

Which type of non-fibrillar collagen is the network forming collagen?

A

Basement membrane collagen

54
Q

Which number types are the fibril-forming collagens?

A

I, II, III, V, XI

55
Q

Fibrils can assemble into what?

A

Fibers

56
Q

Fibers can assemble into what?

A

Bundles (ex. tendons)

57
Q

Where are collagen types I, II, III, V, and XI found?

A

In interstitial connective tissue

58
Q

What collagen types form the major stress bearing component of cartilage, tendons and ligaments?

A

Types I, II, III, V and XI

59
Q

What type of collagen is the most abundant?

A

Type I

60
Q

Where is type I collagen found?

A

In most connective tissue

61
Q

Type I collagen is a major component of what structures?

A 
Bone
Tendon
Skin
Dentin
Ligament
Fascia
Arteries
Uterus
62
Q

Type II collagen is a component of what type of cartilage?

A

Hylaine cartilage

63
Q

Where is type III collagen found?

A

Skin
Arteries
Uterus

64
Q

What type of collagen is prominent in periodontal ligament?

A

Type III collagen

65
Q

Which type of collagen is absent or in very low levels in bone?

A

Type III collagen

66
Q

What are the basement membrane collagens?

A

Types IV, VIII and X

67
Q

What type of collagen is the most abundant structural component of basement membranes?

A

Type IV

68
Q

What makes type VIII collagen?

A

Endothelial cells

69
Q

What make type X collagen?

A

Chondrocytes during endochondral ossification

70
Q

What are the two types of multiplexins?

A

XV

XVIII

71
Q

Where are types XV and XVIII found?

A

In basement membranes

72
Q

What type of domains to multiplexins have?

A

Triple helix domains and interruptions

73
Q

What are fibril associated collagens with interrupted triple helices (FACIT)?

A

Large multidomain molecules with 2 or more short helical rods, separated by small, non-triple helical domains

74
Q

FACIT collagens have large what?

A

N-terminal non-collagen-helix-domain

75
Q

What are the FACIT collagen numbers?

A 
IX
XII
XIV
XVI
XIX
76
Q

Where is type IX collagen found?

A

Cartilage and certain embryonic tissues

77
Q

Where is type XII collagen found?

A

Similar to type I collagen, so it is found in many connective tissues

78
Q

What types of cllagens have several fibrocectin and von Willebrand domains?

A

XII and XIV

79
Q

What shape is type VI collagen?

A

Dumbell-shaped with short helical domain and large globular domain at each end

80
Q

Where are type VI collagens found?

A

Ubiquitous in connective tissue

81
Q

Where are type VI collagens especially abundant?

A

Cornea

82
Q

What is the longest type of collagen with a triple helix?

A

Type VII

83
Q

Where are type VII collagens found?

A

Anchoring fibrils of basement membrane underlying stratified epithelia

84
Q

Collagens are ___ ___.

A

Secreted proteins

85
Q

Where does translation of collagen alpha-chain mRNAs take place?

A

On the rough ER

86
Q

What are the steps of collagen synthesis?

A
  1. Nascent polypeptide chain enters lumen of RER
  2. Signal peptide cleaved off to give procollagen alpha-chain
  3. Hydroxylation of proline and lysine in RER lumen
  4. Hydroxylated lysines can be glycosylated
  5. 3 alpha-chains linked by disulfide bonds at C-terminal; starts procollagen triple helix formation
  6. Procollagen molecules packaged into secretory granules and secreted
87
Q

In collagen synthesis, what occurs in the preprocollagen to procollagen step?

A 
Signal peptide cleaved
Registration peptides
Attach OH to Pro & Lys
Attach sugars to hydroxy-lys
Form triple helix
Package into vesicles
88
Q

In collagen, what occurs in the procollagen to tropocollagen step?

A

Registration peptides cleaved to form insoluble tropocollagen
Tropocollagen aggregates to form fibrils
Fibrils crosslink

89
Q

What are N and C terminals in collagens?

A

Extension called registration peptides that must be proteolytically removed by extracellular enzymes

90
Q

What do procollagen registration peptides prevent?

A

Further assembly of collagen molecules into multimers prior to secretion

91
Q

After secretion, what removes registration peptides?

A

Specific procollagen N and C peptidases

92
Q

How is a mature collagen molecule yielded?

A

After secretion, the registration peptides must be removed

93
Q

What is a mature collagen molecule called?

A

Tropocollagen

94
Q

What can crosslink the modified lysine side chains of collagen?

A

Lysyl oxidase

95
Q

What is needed for full strength in collagen?

A

Cross-links

96
Q

Do cells only secrete one type of fibrillar collagen type?

A

No - they can secrete multiple types

97
Q

With heterogeneous fibrils it is believed that there are 3 types of collagen involved. What are they and how are they structured?

A

Collagen V is the core of the fibril

Types I & II polymerize around it

98
Q

What forms the fiber core of collagen II fibrils?

A

Type XI collagen

99
Q

What regulates fibril morphogenesis?

A

Core collagens

100
Q

What give mechanical strength to fibrils?

A

Bulk collagens

101
Q

What type of domain does collagen IV have?

A

Relatively long triple helical domain

102
Q

How is flexibility generated in collagen IV?

A

Sever small interruptions generate flexible rod

103
Q

What is assembly of collagen VI?

A

assembles into beaded filaments

104
Q

What does collagen VI promote?

A

attachment of fibroblasts and binding to other collagens (widely distributed)

105
Q

What are the beaded filaments associated with in collagen VI?

A

globular domains

106
Q

What does collagen VII do?

A

dimerizes by antiparallel overlapping

107
Q

How are dimers arranged in collagen VII?

A

dimers associated laterally to form 800nm long bundles of fibrils (microfibrils) in basement membrane

108
Q

What type of collagen has an N-terminal domain at each end of that fan out and interact with other ECM components?

A

collagen VII

109
Q

What type of unique collagen is found in hemidesmosomes of epidermal-dermal junctions?

A

collagen XVII

110
Q

What kind of protein is collagen XVII?

A

a transmembrane protein

111
Q

When are tissues remodeled?

A

during normal development, bone growth, and wound healing

112
Q

How do enzymes degrade collagen?

A

specific collagenases hydrolyze collagen peptide bonds that causes fragments to denature and release single chain fragments

113
Q

What type of peptide is much more susceptible to degradation?

A

an open conformation peptide

114
Q

What is cleaved denatured collagen called?

A

gelatin

115
Q

What are gelatinases?

A

denatured collagen that has been further degraded by a variety of enzymes

116
Q

What are some examples of matrix metalloproteinases (MMPs)?

A

collagenase, gelatinase, stromelysin (proteoglycans)

117
Q

What is fibronectin?

A

a ubiquitous ECM glycoprotein

118
Q

What are some characteristics of fibronectin?

A

soluble form in body fluids, insoluble form in ECM, especially basement membranes

119
Q

Where does fibronectin play a major role?

A

in embryogenesis, wound healing, hemostasis, thrombosis

120
Q

Fibronectin is a modular protein that is comprised of what three different modules?

A

Fn1, Fn2, Fn3

MCBM Exam 3 (9 decks)

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