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Biochemistry Post Midterm > Glycosaminoglycans and Glycoproteins > Flashcards

Glycosaminoglycans and Glycoproteins Flashcards

1
Q

What are the three names for GAGs?

A

glycoasminoglycans
proteoglycans
mucopolysacchrides

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2
Q

GAGs are _______, made up of repeating disaccharide units.

A

heteropolysaccharides

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3
Q

GAGs form the body’s what?

A

ground substance in ECM

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4
Q

What are the functions of GAGs?

A 
cell shape maintenance 
adhesion
migration
cell-cell communication
source of growth factors
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5
Q

what is an important characteristic of GAGs?

A

reversible compressibility = resilient

accounts for resilience of synovial fluid and vitreous humor

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6
Q

what are GAGs made up of?

A

amino sugar - D-glucosamine or D-galactosamine

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

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7
Q

what is the exception of keratin sulfate?

A

galactose is present instead of acid sugar

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8
Q

what is the bonding of GAGs?

A

acidic sugar 6C carboxylic acid

N-acetylated amino sugar - 2C amine group

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9
Q

what are the 6 major types of GAGs?

A 
hyaluron
chondroitin sulfate
keratan sulfate
dermatin sulfate
heparin
heparan sulfate
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10
Q

Hyaluronic acid:

What is it made of?

A

D-glucuronic acid

N-Acetyl-D-Glucosamine

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11
Q

Hyaluronic acid:

Special characteristics

A

only GAGs not sulfated

only GAG not found covalently attached to protein core in proteoglycans

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11
Q

Chondroitin sulfate:

where is it found?

A

cartilage
bone
heart valves
MOST ABUNDANT GAG!

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12
Q

Keratan sulfate:

What is it made of?

A

D-Galactose

N-Acetyl-D-glucosamine

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12
Q

Keratan sulfate:

Where is it found?

A

cornea
bone
cartilage
aggregated with chondroitin sulfates

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13
Q

Deramtan sulfate:

Where is it found?

A

skin
blood vessels
heart valves

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14
Q

heparin:

What is it?

A

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

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15
Q

heparan sulfate:

what is it? where is it found?

A

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

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15
Q

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

A

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

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16
Q

each chain contains…?

A

more than 100 monosaccharides

16
Q

what is proteoglycan in cartilage made of?

A

chondroitin sulfate and keratan sulfate attached to a protein core

17
Q

how are carbohydrates and proteins linked?

A

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

17
Q

how do hyaluronic acid associate to proteoglycan monomers?

A

link proteins - non covalent

18
Q

where is protein synthesized?

A

ER

19
Q

where is sugar added? How?

A

Golgi - by glycosyl transferases

20
Q

what are the steps of GAG synthesis?

A

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

21
Q

how are sulfate groups added?

A

PAPs - phosphoadenosinesphosphosulfate

donates sulfate to sugars by sulfotransferase

22
Q

what is heparin?

A

the only intracellular GAG
natural anticoagulant
Slows down coagulation
highly sulfated

23
Q

what does heparin induce?

A

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

24
Q

What is warfarin?

A

used as anticoagulant
synthetic analog of Vitamin K
SLOWER than heparin

25
Q

Structure of GAGs - percentage?

A

90% sugar

10% protein

26
Q

What is UDP used for?

A

activation of sugars - not incorporated

27
Q

structure of glycoproteins - percentages?

A

90% proteins

10% sugars

28
Q

what are the function of membrane-bound glycoproteins?

A

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

29
Q

what are the functions of extracellular matrix of glycoproteins?

A

function as protective biological lubricants

30
Q

many intracellular enzymes are what?

A

glycoproteins - lysosomal enzymes

31
Q

what are mucins?

A

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

32
Q

what is oligosaccharide a mix of?

A

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

33
Q

how are oligosaccharides attached to proteins?

A

N-glycosidic link - amino group of Asparagine

O-glycosidic link - OH group of Ser or Thr

34
Q

how is glycophorin linked?

A

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

35
Q

what are the two classes of N-linked oligosaccharides?

A

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

High mannose oligosaccharides - mannose (Man)

36
Q

what do all N-linked oligosaccharides contain?

A

3 mannose
2 GlcNAc

branched

linked to amide nitrogen of Asparagine

37
Q

what is rich in NANA?

A

mucins

38
Q

what can NANA be in the form of?

A

CMP form

39
Q

what are the three pathways of glycoprotein sorting?

A

membrane proteins
secreted proteins
lysosomal proteins

40
Q

what does the synthesis of N-linked glycosides use?

A

dolichol and dolichol phosphate

Biochemistry Post Midterm (24 decks)

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