ECM II

Question 1

what are glycoconjugates

Answer 1

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

Question 2

name 2 glycans in glycoconjugates

Answer 2

oligosaccharides and GAG

Question 3

what is a glycoprotein

Answer 3

oligosaccharide chains attached to a protein core

Question 4

what is a glycolipid

Answer 4

membrane lipid whose polar head is modified with oligosaccharides

Question 5

what are proteoglycans

Answer 5

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

Question 6

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

Answer 6

N-

O- glycosidic linkages

Question 7

where is the N-glycosidic bond

Answer 7

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

Question 8

the core of N linked glycoproteins is called a

Answer 8

chitobiose: made of 3 mannose and 2 N acetylglucosamine

Question 9

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

Answer 9

• 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

Question 10

where is the O glycosidic bond

Answer 10

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

Question 11

name 2 O-linked core sugars

Answer 11

• xylosyl serine

- galactosyl hydroxylysine

Question 12

as oligosaccharides are

c mobile, give examples of their different conformations

Answer 12

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

Question 13

what are GAG

Answer 13

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

Question 14

the major monosaccharide components of GAG are

Answer 14

• amino sugars

- uronic acids

Question 15

where is hyaluronic acid found

Answer 15

joints and ocular fluids

Question 16

where is chondroitin sulfate found

Answer 16

cartilage, tendons, bone

Question 17

where is dermatan sulfate found

Answer 17

skin, valves, blood vessels

Question 18

where is heparan sulfate found

Answer 18

cell surfaces

Question 19

where is heparin found

Answer 19

mast cells, liver

Question 20

where is keratan sulfate found

Answer 20

cartilage cornea

Question 21

how are GAG attached to the core protein

Answer 21

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

Question 22

how are proteoglycans degraded

Answer 22

in lysosomes.

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

Question 23

what are the functions of proteoglycans

Answer 23

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

Question 24

ECM structural glycoproteins function to?

Answer 24

bind collagens, proteoglycans and cells

are fibronectin and laminin

Question 25

give 4 characteristics of fibronectin

Answer 25

- 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

Question 26

explain the structure of fibronectin

Answer 26

- dimer : due to disulfide bonds at C terminal | - string of beads appearance

Question 27

functions of fibronectin

Answer 27

- cell adhesion, differentiation, growth, migration - anchoring basal lamina to ECM parts - coagulation - embryogenesis - metastasis

Question 28

how are fibronectin fibrils formed

Answer 28

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

Question 29

give 4 charcteristics of laminin

Answer 29

- 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)

Question 30

3 functions of laminin

Answer 30

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

Question 31

give 4 characteristics of integrins

Answer 31

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

Question 32

myosin light chain phosphorylation is mediated by

Answer 32

Rho