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BS202 > 16.2 The Extracellular Matrix and Cell-Matrix Interactions > Flashcards

16.2 The Extracellular Matrix and Cell-Matrix Interactions Flashcards

1
Q

most animal cells are embedded in an () that fills the spaces between cells and binds cells and tissues together

A

extracellular matrix

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2
Q

one type of extracellular matrix is exemplified by the thin, sheetlike () upon which layers of epithelial cells rest

A

basal laminae

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3
Q

EC matrix is most abundant in ()

A

connective tissues (e.g. tendons, cartilage, bone matrix)

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4
Q

the 3 major components of the EC matrix

A
  1. matrix structural proteins
  2. matrix polysaccharides
  3. adhesion proteins
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5
Q

matrix structural proteins are predominantly ()

A

collagens (type I and IV)

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6
Q

composed principally of a protein called elastin → cross-linked into a network by covalent bonds formed between side chains of lysine residues (similar to those found in collagen)

A

elastic fibers

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7
Q

elastic fibers are principally composed of a protein called ()

A

elastin

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8
Q

how are elastic fibers cross-linked into a network

A

cross-linked by covalent bonds formed between side chains of lysine residues

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9
Q

differences between various types of EC matrices result from both (1) and from (2)

A
  1. quantitative variations in the types of amounts of EC components
  2. modifications in their organization
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10
Q

similar to plant cell walls, EC matrices are composed of (1) embedded in a (2)

A
  1. tough, fibrous proteins
  2. gel-like polysaccharide ground substance
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11
Q

the major structural protein of the extracellular matrix; single most abundant protein in animal tissues

A

collagen

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12
Q

collagen is characterized by the formation of ()

A

triple helices

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13
Q

collagen triple helix domain consist repeats of the amino acid sequence ()

A

Gly-X-Y

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14
Q

in the collagen triple helix domain amino acid sequence Gly-X-Y, X is usually (1) and Y is usually (2)

A
  1. proline
  2. hydroxyproline
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15
Q

in the collagen triple helix, () is required in every third position in order for the polypeptide chains to pack together close enough to form the collagen triple helix

A

glycine

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16
Q

one of the fibril-forming collagens that are the basic structural components of connective tissues; most abundant type of collagen

A

type I collagen

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17
Q

after secretion, type I collagens assemble into () in which the triple helical molecules are associated in staggered arrays

A

collagen fibrils

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18
Q

collagen fibrils do not form inside the cell because they are synthesized as soluble precursors called ()

A

procollagens

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19
Q

procollagens contain () at both ends of the polypeptide chain; cleaved outside the cell to produce collagen

A

nonhelical segments

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20
Q

covalent cross-links between side chains of () residues help strengthen the fibrils (composed of type I collagen)

A

lysine and hydroxylysine

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21
Q

collagen fibrils further associate with each other to form (), which can be several µm in diameter

A

collagen fibers

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22
Q

network-forming collagen that forms the basal laminae

A

type IV collagen

23
Q

type IV collagen is more flexible than type I collagen (that form fibrils), thus allowing it to (…)

A

assemble into 2D cross-linked networks instead of fibrils

24
Q

other types of collagens form (), which link basal laminae to underlying connective tissues

A

anchoring fibrils

25
Q

some collagens are () that participate in cell-matrix interactions

A

transmembrane proteins

26
Q

fibrous structural proteins of the EC matrix are embedded in gels formed from polysaccharides called ()

A

glycosaminoglycans (GAGs)

27
Q

glycosaminoglycans (GAGs) consist of repeating units of the ff. disaccharides:

A
  1. either N-acetylglucosamine or N-acetylgalactosamine
  2. acidic disaccharides (either glucuronic acid or iduronic acid)
28
Q

with the exception of hyaluronan, sugars of GAGs are modified by the (1) → GAGs are highly (2)

A
  1. addition of sulfate groups
  2. negatively charged
29
Q

like pectin, GAGs () to form hydrated gels → provide mechanical support to the EC matrix

A

bind cations and trap water molecules

30
Q

moreover, () is the only GAG that occurs as a single long polysaccharide chain

A

hyaluronan

31
Q

hyaluronan is synthesized at the PM by () (transmembrane protein)

A

hyaluronan synthase

32
Q

() contain GAG chains covalently bonded to serine residues of a core protein; interact with hyaluronan to form large complexes in the EC matrix

A

proteoglycans

33
Q

proteoglycans can consist of up to 95% () by weight

A

polysaccharide

34
Q

() are responsible for linking the components of the matrix to one another and to the surfaces of cells

A

adhesion proteins

35
Q

adhesion proteins are the major binding sites for ()

A

cell surface receptors

36
Q

adhesion proteins interact with (1) and (2) to specify matrix organization

A
  1. collagen
  2. proteoglycans
37
Q

prototype of adhesion proteins; principal adhesion protein of connective tissues

A

fibronectin

38
Q

fibronectin is a () composed of 2 polypeptide chains (each containing about 2.5k amino acids)

A

dimeric glycoprotein

39
Q

dimers of glycoprotein form fibronectin by cross-linking into fibrils by ()

A

sulfate bonds

40
Q

how is fibronectin able to cross-link matrix components

A

it contains binding sites for both collagen and proteoglycans

41
Q

in addition to binding sites for collagen and proteoglycans, fibronectin also contains a distinct site that is recognized by ()

A

integrins

42
Q

principal adhesion molecules of the basal lamina

A

laminin

43
Q

describe the structure of laminins

A

cross- or T-shaped heterotrimers; can self-assemble into meshlike networks

44
Q

laminins are composed of 3 subunits

A
  1. long alpha main chain
  2. beta and gamma side “arms”
45
Q

how do laminins link matrix components to one another and to the cell surface?

A

different laminin subunits have binding sites for cell surface receptors (e.g. integrins) and proteoglycans

46
Q

binds to laminins and is tightly associated to type IV collagen

A

nidogen

47
Q

major cell surface receptors responsible for the attachment of cells to the EC matrix

A

integrins

48
Q

integrins are composed of 2 subunits (1), the former of which bind (2)

A
  1. alpha and beta
  2. divalent cations
49
Q

how do integrins attach EC components to PM

A

they bind to short amino acid sequences present in multiple components of the EC matrix (including collagen, fibronectin, laminin, and proteoglycans)

50
Q

moreover, () on cell surfaces can also bind to EC matrix components and modulate cell-matrix interactions

A

transmembrane proteoglycans

51
Q

how do integrins also serve as anchors for the cytoskeleton

A

linkage between cytoskeleton and EC matrix is responsible for the stability of cell-matrix junctions

52
Q

distinct interaction between integrins and the cytoskeleton are found at 2 types of cell-matrix junctions:

A
  1. focal adhesions
  2. hemidesmosomes
53
Q

describe integrin function in focal adhesions

A
  • attach a variety of cells (including fibroblasts) to the EC matrix
  • cytoplasmic domains of the integrin beta subunits anchor the actin cytoskeleton by associating with bundles of actin filaments
54
Q

describe integrin function in hemidesmosomes

A
  • mediate epithelial cell attachments at which the alpha-6-beta-4 integrin is linked to intermediate filaments and laminin (via plectin) → anchors epithelial cells to basal lamina

BS202 (36 decks)

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