ECM Flashcards

1
Q

4 functions of the extracellular matrix

A
  1. physical strength/ structural support
  2. cell shape and behaviour
  3. storage of growth factors
  4. tissue repair
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2
Q

the 2 major types of molecules in the ECM

A

fibrillar proteins and glycosaminoglycans

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3
Q

what are glycosaminoglycans

A

glycosaminoglycans are polysaccaride chains covalently bound to proteins to form a proteoglycan

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4
Q

the 2 kinds of fibrillar proteins and their functions

A

collagens for structure

fibronectin as adhesive glycoprotein

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5
Q

what is the structure of fibrillar collagen

A

3 polypeptide chains wound around each other to form a superhelix structure

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6
Q

what is the amino acid sequence of collagen

A

glycine-X-Y repeated sequence
X is often proline
Y is often hydroxyproline

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7
Q

how does glycine’s structure contribute to its importance in collagen

A

its the smallest amino acid with one hydrogen as its side chain
its the only amino acid small enough to fit in middle of the triple helix so allows the 3 polypeptide chains to intertwine tightly

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8
Q

why is hydroyxproline so important

A

it stabilises the triple helix by forming additional hydrogen bonds and holding proline ring in a conformation that helps stabilise the helix

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9
Q

3 different types of collagen

A

fibril forming
fibril associated
networking (fishnet) making

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10
Q

intracellular steps of collagen synthesis

A
  1. cleavage of signal peptide on N terminus
  2. hydroxylation of proline and lysine residues
  3. glycosylation of proline resides
  4. N and C propeptides of polypeptides facilitate winding into helices, chaperone proteins prevent misfolding
  5. pacakged into vesicles and further processed in Golgi
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11
Q

extracellular steps of fibrillar collagen synthesis

A
  1. cleavage of the N and C propeptides
  2. self assembly of the triple helical rods into long fibrils
  3. crosslink formation between the fibrils
  4. binding of fibril associated proteins
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12
Q

how are collagen crosslinks formed

A

there are short segments of hydroxylysine at the end of collagen molecules (not associated with the triple helix)
Lysyl oxidase catalyses the formation of covalent intermolecular crosslinks

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13
Q

why is vitamin c so important

A

it is a cofactor for propyl hydroxylase which catalyses formation of hydroxyproline from proline
hydroxyproline is crucial for stability in collagen
scurvy leads to gradual loss of collagen

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14
Q

how do collagen fibrils associate with other proteins

A

proteoglycans and non -fibrillar collagens regulate orientation and size of the fibrils

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15
Q

what allows connective tissues to stretch and what do they contain

A

elastic fibres which are not related to collagen

these contain elastin and glycoproteins like fibrillin

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