Glycosaminoglycans and Glycoproteins Flashcards Preview

Biochemistry Post Midterm > Glycosaminoglycans and Glycoproteins > Flashcards

Flashcards in Glycosaminoglycans and Glycoproteins Deck (45):
1

What are the three names for GAGs?

glycoasminoglycans
proteoglycans
mucopolysacchrides

2

GAGs are _______, made up of repeating disaccharide units.

heteropolysaccharides

3

GAGs form the body's what?

ground substance in ECM

4

What are the functions of GAGs?

cell shape maintenance
adhesion
migration
cell-cell communication
source of growth factors

5

what is an important characteristic of GAGs?

reversible compressibility = resilient
accounts for resilience of synovial fluid and vitreous humor

6

what are GAGs made up of?

amino sugar - D-glucosamine or D-galactosamine
acidic sugar - D-glucuronic acid or C-5 epimer: L-iduronic acid

7

what is the exception of keratin sulfate?

galactose is present instead of acid sugar

8

what is the bonding of GAGs?

acidic sugar 6C carboxylic acid
N-acetylated amino sugar - 2C amine group

9

what are the 6 major types of GAGs?

hyaluron
chondroitin sulfate
keratan sulfate
dermatin sulfate
heparin
heparan sulfate

10

Hyaluronic acid:
What is it made of?

D-glucuronic acid
N-Acetyl-D-Glucosamine

11

Hyaluronic acid:
Special characteristics

only GAGs not sulfated
only GAG not found covalently attached to protein core in proteoglycans

11

Chondroitin sulfate:
where is it found?

cartilage
bone
heart valves
MOST ABUNDANT GAG!

12

Keratan sulfate:
What is it made of?

D-Galactose
N-Acetyl-D-glucosamine

12

Keratan sulfate:
Where is it found?

cornea
bone
cartilage
aggregated with chondroitin sulfates

13

Deramtan sulfate:
Where is it found?

skin
blood vessels
heart valves

14

heparin:
What is it?

components of intracellular granules of mast cells lining the arteries of lungs, liver and skin



more sulfated than heparan sulfates

the only intracellular GAG
natural anticoagulant
Slows down coagulation
highly sulfated

15

heparan sulfate:
what is it? where is it found?

basement membranes
components of cell surfaces
contains higher acetylated glucosamine than heparin

15

All GAGs (except for hyaluronic acid) are attached to what?

to a protein core = proteoglycan monomers
structure resembles a "bottle brush"

act as a scaffold of which you can attach other GAGs to form larger proteoglycan aggregates

16

each chain contains...?

more than 100 monosaccharides

16

what is proteoglycan in cartilage made of?

chondroitin sulfate and keratan sulfate attached to a protein core

17

how are carbohydrates and proteins linked?

through a trihexoside (Gal-Gal-Xylose) and a Ser residue

17

how do hyaluronic acid associate to proteoglycan monomers?

link proteins - non covalent

18

where is protein synthesized?

ER

19

where is sugar added? How?

Golgi - by glycosyl transferases

20

what are the steps of GAG synthesis?

syn. of amino sugars
syn. of acidic sugars
syn. of core protein
syn. of carbohydrate chain
addition of sulfate groups

21

how are sulfate groups added?

PAPs - phosphoadenosinesphosphosulfate
donates sulfate to sugars by sulfotransferase

22

what is heparin?

the only intracellular GAG
natural anticoagulant
Slows down coagulation
highly sulfated

23

what does heparin induce?

the release of cell surface associated TFPI, anti-thrombin III

24

What is warfarin?

used as anticoagulant
synthetic analog of Vitamin K
SLOWER than heparin

25

Structure of GAGs - percentage?

90% sugar
10% protein

26

What is UDP used for?

activation of sugars - not incorporated

27

structure of glycoproteins - percentages?

90% proteins
10% sugars

28

what are the function of membrane-bound glycoproteins?

cell-surface recognition (receptors)
cell surface antigenicity
contribute to glycocalyx and cell protection

29

what are the functions of extracellular matrix of glycoproteins?

function as protective biological lubricants

30

many intracellular enzymes are what?

glycoproteins - lysosomal enzymes

31

what are mucins?

large glycoproteins
negatively charged sialic acid, N-acetyl neuraminic acid (NANA)
occupy a large space
trap water and serves as protective barriers

32

what is oligosaccharide a mix of?

D-hexoses
NANA
L-fucose (6-deoxy-L-galactose)
C6 has a methyl group

33

how are oligosaccharides attached to proteins?

N-glycosidic link - amino group of Asparagine
O-glycosidic link - OH group of Ser or Thr

34

how is glycophorin linked?

O-linked to hydroxyl group in Ser and Thr by N-acetylgalactosamine

35

what are the two classes of N-linked oligosaccharides?

complex oligosaccharides - N-acetylglucoamine (GlcNAc), L-fucose (Fuc), NANA

High mannose oligosaccharides - mannose (Man)

36

what do all N-linked oligosaccharides contain?

3 mannose
2 GlcNAc

branched

linked to amide nitrogen of Asparagine

37

what is rich in NANA?

mucins

38

what can NANA be in the form of?

CMP form

39

what are the three pathways of glycoprotein sorting?

membrane proteins
secreted proteins
lysosomal proteins

40

what does the synthesis of N-linked glycosides use?

dolichol and dolichol phosphate