Glycosaminoglycans And Glycoproteins

Question 1

Basic Description of GAGs

Answer 1

Heteropolysaccharides made up of repeating disaccharide units

Question 2

relationship between glycosaminoglycan structure and function

Answer 2

The strong negative charges (-Coo- and -Oso3-) cause the molecule to fan outwards and repel adjacent molecules

Question 3

GAG water binding

Answer 3

The negative charges allow the molecule to bind water, leading to each molecule being surrounded by a hydrated shell that gives them compressibility and the ability to spring back to their original shape (resilience).

Question 4

What accounts for the resilience of synovial fluid and vitreous humor?

Answer 4

Reversible compressibility of the water shell around GAG molecules

Question 5

What is the repeating subunit that makes up all GAGs?

Answer 5

Acidic sugar-amino sugar

Question 6

What are the possible amino sugars in GAGs?

Answer 6

D-glucosamine and D-galactosamine

Question 7

What are the acidic sugars that make up GAGs?

Answer 7

D-glucuronic acid or the C-5 epimer L-iduronic acid

Question 8

What is the exception to the acidic sugar rule?

Answer 8

Keratin sulfate where galactose is present instead of an acid sugar

Question 9

Hyaluron

Answer 9

Found in the synovial fluid, vitreous humor, and ECM of loose connective tissue. Large polymers are shock absorbing. Only GAG that doesn’t contain sulfate and only GAG that doesn’t covalent lay attach to proteins in proteoglycans

Question 10

Chondroitin Sulfate

Answer 10

found in the cartilage,bone, heart valves. Most abundant GAG.

Question 11

Keratan Sulfate

Answer 11

Found frequently with other GAGs. Found in the cornea, bone, and cartilage with chondroitin sulfates

Question 12

Dermatan Sulfates

Answer 12

Skin, blood vessels, and heart valves

Question 13

Heparin

Answer 13

Only intracellular GAG. Component of intracellular granules of mast cells lining the arteries of the lungs, liver, and skin. More Sulfates than heparan

Question 14

Heparan Sulfate

Answer 14

Makes up basement membranes, components of cell surfaces. More acetylated glucosamine than heparin

Question 15

What is hylauronic acid attached to?

Answer 15

Just a sugar, not a protein like all other GAGs

Question 16

The proteoglycan in cartilage is made up of…

Answer 16

Chondroitin sulfate and keratin sulfate attached to a protein core

Question 17

What links carbohydrates and proteins in proteoglycans?

Answer 17

A serine attaches a linking sugar of Gal-Gal-Xyl (tri-hexoside) to the protein core

Question 18

Where are GAGs synthesized?

Answer 18

In the ER and then modified in the Golgi (where acid/amino sugar glycosylation occurs)

Question 19

Glycosyl Transferases

Answer 19

Enzymes that catalyze the elongation of polysaccharide chains by alternate placement of their UDP derivatives

Question 20

Addition of sulfate groups to the proteoglycan:

Answer 20

PAPS donates a sulfate(in the Golgi). Requires sulfotransferase.

Question 21

role of heparin

Answer 21

Prevents coagulation of blood (inhibits blood clotting)

Question 22

Tissue Factor Pathway Inhibitor

Answer 22

TFPI (anti-thrombin III). Mainly supplied by endothelial cells. It is an inhibitor that comes into action when limited quantities of factor Xa are generated. TFPI binds to factor Xa and then to tissue factor VIIa forming an inactive quaternary complex. Heparin induces the release of TFPI.

Question 23

Warfarin

Answer 23

Anticoagulant. Synthetic analog of VitK. Acts slower than heparin so it is administered after

Question 24

What are the major roles of glycoproteins?

Answer 24

Cell surface receptors. (G-proteins), blood type determinant, in collagen, and serve as a protective barrier, and make up intracellular/lysosomal enzymes.

Question 25

What is a glycoprotein?

Answer 25

Protein with attached oligosaccharide.

Question 26

What do extracellular matrix glycoproteins do?

Answer 26

Act as protective biological lubricants

Question 27

What determines the blood type?

Answer 27

Combination of sugars on the glycoproteins

Question 28

Mucin

Answer 28

Large glycoproteins with negatively charged sialic acid, NANA.They occupy a large space and trap water,serving as a protective barrier.

Question 29

O-glycosidic Link

Answer 29

Oligosaccharide attached to the OH group on Serine or Threonine

Question 30

N-glycosidic Link

Answer 30

Oligosaccharide attached to the amide group of asparagine

Question 31

What links the oligosaccharides to the hydroxyl groups?

Answer 31

N-acetylgalactosamine

Question 32

What are the two types of N-linked oligosaccharides?

Answer 32

Complex (diverse group of additional sugars) and high mannose (primarily mannose)

Question 33

What is the charge of an oligosaccharide when NANa is present?

Answer 33

Negative

Question 34

Synthesis of O-linked glycosides

Answer 34

Protein is synthesized in rER and then extruded into lumen of ER. Glycosylation occurs in the Golgi through specific glycosyltransferases that add sugars sequentially.

Question 35

Degradation of GAGs

Answer 35

GAGs, glycoproteins, and glycolipids occurs in lysosomes following their endocytosis

Question 36

Mucoploysaccharidosis

Answer 36

Inability to degrade with GAGs or glycoproteins

Question 37

Sphingolipidosis

Answer 37

Inability to degrade sphingolipids

Question 38

I-Cell disease

Answer 38

Rare syndrome in which hydrolytic enzymes normal found in lysosomes are absent, lack the ability to phosphorylase mannose residues. Usually caused by an issue with protein targeting.

Question 39

Enzymes destined for lysosomes

Answer 39

Usually bound my Mannose-6-phosphate which target the enzymes to facilitate their translocation to lysosomes. Typically hydrolytic enzymes (proteases, lipases, etc..)