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Biochemistry Year 2 > ECM II > Flashcards

ECM II Flashcards

1
Q

what are glycoconjugates

A

are proteins or lipids that contain covalently linked glycan (sugar) chains

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2
Q

name 2 glycans in glycoconjugates

A

oligosaccharides and GAG

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3
Q

what is a glycoprotein

A

oligosaccharide chains attached to a protein core

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4
Q

what is a glycolipid

A

membrane lipid whose polar head is modified with oligosaccharides

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5
Q

what are proteoglycans

A

a core protein linked to many GAG chains. Use the bottle brush model

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6
Q

what are the 2 types of linkages that can be present in glycoproteins

A

N-

O- glycosidic linkages

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7
Q

where is the N-glycosidic bond

A

between N-acetylglucosamine and the NH2 in the side chain of an Asn residue

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8
Q

the core of N linked glycoproteins is called a

A

chitobiose: made of 3 mannose and 2 N acetylglucosamine

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9
Q

3 steps of c-post-translational processing of N-linked glycoproteins

A
  • they have a specific motif that is read by glycosylation machinery (this performs the initial glycosylation process while its being synthesized in the RER)
  • oligosaccharides are attached
  • processing in the ER, golgi and then attachment of other monosaccharides
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10
Q

where is the O glycosidic bond

A

between Xyl, Gal, GalNAc and the OH on the side chain of Ser/Thr residue

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11
Q

name 2 O-linked core sugars

A
  • xylosyl serine

- galactosyl hydroxylysine

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12
Q

as oligosaccharides are

c mobile, give examples of their different conformations

A

erythrocyte glycocalyx - helps antigen blood recognition and flowing through small capillaries

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13
Q

what are GAG

A

long carbohydrate polymers made of repeating disaccharide units. Are -vely charged due to sulfate and uronic acid groups.

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14
Q

the major monosaccharide components of GAG are

A
  • amino sugars

- uronic acids

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15
Q

where is hyaluronic acid found

A

joints and ocular fluids

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16
Q

where is chondroitin sulfate found

A

cartilage, tendons, bone

17
Q

where is dermatan sulfate found

A

skin, valves, blood vessels

18
Q

where is heparan sulfate found

A

cell surfaces

19
Q

where is heparin found

A

mast cells, liver

20
Q

where is keratan sulfate found

A

cartilage cornea

21
Q

how are GAG attached to the core protein

A

all (except hyaluronic acid) attach to Ser/Thr residue via Gal-Gal-Xyl
keratan sulfate is both free and bound. KS I is N linked, KS II is O-linked

22
Q

how are proteoglycans degraded

A

in lysosomes.

protein core is hydrolysed by proteases, GAG are degraded by acid hydrolases

23
Q

what are the functions of proteoglycans

A

Occupy space between cells and collagen
Organize water molecules
• Highly viscous - lubricating fluid in the joints
• Specific binding to other macromolecules
• Associate with collagen fibers - network - in the bone, combine with calcium salts (calcium carbonate, hydroxyapatite)
• Anchoring of cells to matrix fibers
• Cell migration and adhesion

24
Q

ECM structural glycoproteins function to?

A

bind collagens, proteoglycans and cells

are fibronectin and laminin

25
Q

give 4 characteristics of fibronectin

A
  • is a high weight glycoprotein
  • binds to integrins
  • cellular fibronectin produced by fibroblasts is assembled into insoluble fibrils
  • plasma fibronectin produced by hepatocytes circulates in a soluble form
26
Q

explain the structure of fibronectin

A
  • dimer : due to disulfide bonds at C terminal

- string of beads appearance

27
Q

functions of fibronectin

A
  • cell adhesion, differentiation, growth, migration
  • anchoring basal lamina to ECM parts
  • coagulation
  • embryogenesis
  • metastasis
28
Q

how are fibronectin fibrils formed

A
  • soluble fibronectin binds integrins
  • this binding induces reorganization of actin filaments and signaling
  • cell contractiliy leads to changes i FN formation, forming fibrls
29
Q

give 4 charcteristics of laminin

A
  • high weight glycoprotein
  • heterotrimeric
  • undergo reversible self association to form polymers in Ca presence
  • interacts with integrins via multiple binding sites
  • binds ECM components, including heparan sulfate (directly), and collagen IV (mostly indirectly via nidogen/entactin)
30
Q

3 functions of laminin

A
  • cell adhesion
  • cell differentiation
  • conjunction with entactin, LN generates a scaffold for anchoring of cells and ECM molecules in the basement membrane
31
Q

give 4 characteristics of integrins

A
  • adhesion molecules
  • can transduce signals from ECM leading to change in cell morphology
  • need to be activated by inside-out signaling
32
Q

myosin light chain phosphorylation is mediated by

A

Rho

Biochemistry Year 2 (11 decks)

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