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Cell Bio > Extracellular matrix and cell interactions > Flashcards

Extracellular matrix and cell interactions Flashcards

1
Q

what does ECM stand for

A

extracellular matrix

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2
Q

how are tissues held together

A
  • cell-cell adhesions
  • extracellular matrix
  • or both
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3
Q

what is the ECM

A

large network of secreted molecules that surround, support, and give structure to cells and tissues

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4
Q

what is ECM composed of in plant systems (and give examples)

A
  • primarily carbohydrates
  • ex cellulose and pectin (predominant in the cell wall)
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5
Q

what is ECM composed of in animal systems (and give examples)

A
  • primarily proteins
  • ex. collagen (most common, but varies by tissue type)
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6
Q

what are the four major types of tissues

A
  • connective
  • epithelial
  • nervous
  • muscle
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7
Q

describe the organization of connective tissue

A

cells are loosely organized, attached to one another, rigid scaffold, or both

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8
Q

describe how connective tissue carries mechanical load

A
  • EMC is abundant
  • carries the mechanical load
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9
Q

describe the structure of epithelial tissue

A

sheets of polarized cells with discrete functions at apical and basal ends

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10
Q

describe how epithelial tissue carries mechanical load

A
  • EMC is sparse
  • cells are directly joined to one another and carry the mechanical load
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11
Q

is animal connective tissue varied

A

enormously

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12
Q

the bulk of connective tissue is composed of what

A
  • EMC
  • and the cells that produce the matrix are scattered within
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13
Q

the tensile strength of connective tissue is provided by what

A
  • fibrous proteins
  • primarily collagens
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14
Q

what is the role of fibrous proteins/ collagens in connective tissue

A

provides tensile strength

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15
Q

what determines connective tissue characteristics

A

type and quantity of collagen (as well as other molecules)

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16
Q

what are collagens and what is their role

A
  • a family of proteins that come in many variety
  • supports the structure and function of diff tissues
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17
Q

describe the typical structure of collagen molecules

A
  • long
  • stiff
  • triple helices in which 3 polypeptide chains are wound around each other
  • sometimes assemble into collagen fibral and collagen fibers
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18
Q

what is collagen secreted as

A
  • procollagen
  • with additional peptide extensions at each end to prevent premature assembly
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19
Q

what does procollagen proteinases do

A

cleave the procollagen terminal extensions once in the ECM

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20
Q

what cleaves the procollagen terminal extensions once in the ECM

A

extracellular enzymes called procollagen proteinases

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21
Q

where are cells that manufacture collagen and other ECM molecules, and how are they named

A
  • reside within the connective tissue matrix
  • named according to tissue type
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22
Q

where are collagen and other ECM molecules produced

A
  • mostly intraceullarly
  • then secreted via exocytosis before assembly into aggregates
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23
Q

what does collagen organization contribute to

A

tissue characterization

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24
Q

how is collagen organized in skin and why

A
  • woven into alternating layers w diff orientations
  • to resist tensile stress in multiple directions
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25
Q

how is collagen organized in tendons and why

A
  • aligned in parallel bundles along the major axis of tension
  • attaches muscle to bone, only one main axis of tension
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26
Q

what organizes collagen as they move along the filaments

A

cells that secrete collagen

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27
Q

cells that interact with collagen in the ECM via transmembrane receptor proteins are called what

A

integrins

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28
Q

what are integrins

A

cells that interact with collagen in the ECM via transmembrane receptor proteins

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29
Q

how do integrins interact with collagen

A
  • not directly
  • through another ECM protein called fibronectin
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30
Q

describe how fibronectin helps bind integrins and collagen

A
  • Fibronectin molecules bind to collagen fibrils outside the cell
  • Integrins in the plasma membrane bind to the fibronectin and tether it to the cytoskeleton inside the cell
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31
Q

what domain interacts with the cell cytoskeleon

A

intracellular domain

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32
Q

what domain binds to components of the matrix

A

extracellular domain

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33
Q

formation and breakage of attachments at either end of an integrin molecule allows what

A

many cells to crawl through tissues

34
Q

integrin binding to a molecule on one end leads to what

A
  • conformational changes at the other end
  • extends in an activated state so that it can latch onto a molecule on the opposite side
35
Q

what are the main ways to activate an integrin

A
  • intracellular signaling molecule can activate it from the cytoplasmic side
  • binding to an external structure can trigger itracellular signaling pathways by activating protein kinases that associate w the intracellular end of the integrin
36
Q

what do GAGs stand for

A

glycosaminoglycans

37
Q

what is the role of GAGs

A

aid tissues in resisting compression

38
Q

describe the structure of GAGs

A
  • negatively charged polysaccharide chains made of repeating disaccharide units
  • in each disaccharide, one of the monomers is an amino sugar
39
Q

describe the structure of proteoglycans

A
  • chains of GAGs covalently linked to a core protein
  • resembles a bottle brush
40
Q

what makes GAGs good space fillers

A

tend to adopt extensive conformations which occupy large volumes relative to their mass

41
Q

how do GAGs increase swelling pressure

A
  • strongly hydrophillic
  • multiple neg charges attract cations which draw water into the ECM
  • this gives rise to swelling pressure
42
Q

in dense + compact connective tissues (bone or tendon), what is the ratio of GAGs and collagen

A
  • low amount of GAGs
  • high amount of collagen
43
Q

in loose connective tissues (inside of eye), what is the ratio of GAGs and collagen

A
  • high amount of GAGs
  • low amount of collagen
44
Q

describe the overall structure of epithelia

A
  • multicellular sheets in which adjacent cells are joined tightly together
  • cells present in many diff forms, a sheet may be homogenous or comprised of diff types
45
Q

what is stratified epithelia

A

multicellular sheet is many cells thick

46
Q

what is simple epithelia

A

multicellular sheet is one cell thick

47
Q

what are 4 types of epithelia cells

A
  • columnar
  • cuboidal
  • squamous
  • stratified
48
Q

what is the function of epithelia

A
  • many functions including secretion and nutrient uptake
  • nearly all sheets form a barrier
  • same significance to multicellular organisms and plasma membranes do to a single cell
49
Q

what are the 2 faces of epithelial sheets

A
  • apical exposed to air or bodily fluid
  • basal attached to basal lamina
50
Q

what is the basal lamina

A

thing, tough sheet of the ECM

51
Q

describe the structure of the basal lamina

A

mainly composed of type IV collagen and a protein laminin

52
Q

what does laminin do

A

provides linkage sites for integrin molecules in basal plasma membrane

53
Q

describe the polarity of epithelia

A
  • reflects the polarized organization of its individual epithelial cells
  • each w an apical and basal surface w diff properties and functions
54
Q

is polarity important for epithelial function

A

yes

55
Q

what cell type is present in mammalian small intestin

A
  • simple columnar epithelium primarily consisted of 2 cell types
  • absorptive cells
  • goblet cells
56
Q

what do absorptive cells do

A
  • take up nutrients at their apical surface
  • export to underlying tissues at the basal surface
57
Q

what do goblet cells do

A
  • synthesize mucus
  • discharge it at the apical surface to lubricate and protect the gut lining
58
Q

the polarity of the simple columnar epithelium depends on what

A
  • the junctions formed between neighbouring cells
  • the basal lamina
59
Q

what are the different kinds of epithelial cell junctions

A
  • tight junctions
  • adherens junction
  • desmosome
  • gap junction
  • hemidesmosome
60
Q

what is the role of tight junctions

A
  • seals neighbouring cells together, preventing water-soluble molecules from leaking
61
Q

where are tight junctions formed from

A

proteins called claudins and occludins arranged in strands to create a seal

62
Q

how do tight junctions maintain polarity

A
  • prevent diffusion of membrane proteins from the apical surface to the basolateral surface
  • serve as assembly sites for protein complexes that govern polarity
63
Q

what are the types of cytoskeleton-linked junctions

A
  • adherens
  • desmosomes
  • hemidesmosomes
64
Q

which cytoskeleton-linked junctions bind one epithelial cell to another

A
  • adherens
  • desmosomes
65
Q

which cytoskeleton-linked junctions bind epithelial cells to the basal lamina

A

hemidesmosomes

66
Q

how do adheren junctions work

A
  • uses transmembrane proteins from the cadherin family, which require Ca2+ to interact w one another
  • each cadherin is tethered inside to actin filaments via linker proteins
  • junctions form a continuous belt around interacting cells near the apical end
67
Q

what allows epithelium to change shape in adherens junctions

A

actin network

68
Q

how does the actin network change the shape of epithelium

A
  • contracting along one axis, rolling itself into a tube
  • or by contracting along multiple axes, the sheet can form a hollow sphere
69
Q

when is the formation of epithelial cell tubes critical

A
  • during embryonic development
  • gives rise to structures including the neural tube and lens vesicle
70
Q

describe desmosome junctions

A
  • different set of cadherin molecules connect to keratin filaments
  • bundles of keratin filaments are anchored via desmosome junctions to similar bundles in adjacent cells
71
Q

what provides great tensile strength to the epithelial sheet

A
  • the arrangement of keratin filaments in desmosome junctions
  • key characteristic of exposed epithelia (skin)
72
Q

why are hemidesmosomes named

A

they look like half of a desmosome

73
Q

how do hemidesmosomes work

A
  • anchor cells to the basal lamina via integrins in the cell basal membrane
  • integrins bind to laminin in the basal lamina and bind to keratin via linker proteins inside the cell
74
Q

where are gap junctions found

A

in all epithelia and many other animal tissues

75
Q

what do gap junctions form

A

water-filled channels that allow inorganic ions and small water-soluble molecules to move directly from the cytosol of one cell to another

76
Q

where are gap junctions located

A
  • regions where the plasma membranes of 2 cells lie close together (and exactly parallel)
  • they span by protruding ends of transmembrane protein complexes called connexons
77
Q

the flow of ions and small molecules between cells creates what

A

an electric and metabolic coupling between them

78
Q

when can gap junctions be opened and closed

A

in response to extra- or intracellular signals

79
Q

what allows for spread of electrical current through cardiac cells triggering coordinated contractions

A
  • gap junction permeability
  • the flow of ions and small molecules between cells
80
Q

what do gap junctions connect

A

the cytosol of one cell to another

81
Q
A

Cell Bio (11 decks)

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