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34 Cards in this Set

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What are GAG's?
Glycosaminoglycans
long, unbranched and contain repeating disaccharide unit
Most abundant polysaccharide in the body
what is used to form GAGs?
Heteropolysaccharides
contain 13 different monosaccharides and monosaccharide derivatives
Glucuronic acid
Iduronic acid
Galactose
N-acetylglucosamine
N0acetylgalactoseamine
What is the function of GAG's?
highly negatively charged with extended conformation that imparts high viscosity to a solution:
Synovial fluid & Cartilage
The rigidity provides structural integrity to cells and provides passageways between cells allowing for cell migration
where are GAGs primarily located?
surface of cell's or in the ECM
why are GAGs ideal for lubricating fluids in the joints?
Low compressibility
How many different kinds of GAGs do we produce?
6
what makes each GAG distinctive?
Repeating disaccharide unit makes them distinctive
One of the monosaccharides in the disaccharide is always an AMINO sugar
what is the most prevalent GAG?
Chondrotin sulfate
what GAG has the highest negative charge?
Heparin
What GAG has been successfully used in supplement form to help improve human cartilage formation?
Chondrotin sulfate
What are PROTEOGLYCANS?
GAGs attached to a protein backbone
Carbohydrate composition is up to 97%
more carbohydrate than protein
how is the carbohydrate attached to the protein in a proteoglycan?
O-linked
attached to protein via hydroxyl group of serine
what are the functions of Proteoglycans?
Structural: elastic space filler
Limit diffusion of macromolecules
Impede passage of microbes
Acts a lubricants of joints
Regulate cell motility and adhesion
Sequestration of growth factors, local enzymatic action
Present hormones to cell surface receptors
How are proteoglycans formed?
Protein is synthesized and carbohydrate is added in rER
GAGs are synthesized in the golgi and then added to the carbohydrate that has already been attached to the serine group in the protein using a covalent glycosidic bond
Addition of sulfate to the GAGs also occurs in the golgi
Hyaluronic acid and the proteoglycans are secreted from the cell
Outside of the cell the proteoglycan is attached to hyaluronic acid using two linker glycoproteins
What proteoglycan is used to make cartilage?
Aggrecan
the biggest GAG
one of two ECM proteoglycans
How is cartilage formed?
Hyaluronana backbone, linker proteins attach to core proteins, GAGs attach to core proteins
Hyaluronate is the backbone but it is not used to synthesize the proteoglycans that will be attached to it.
Assembly of the proteoglycans occurs outside the cell
How does cartilage work?
The GAGs are highly negatively charged
Water is attracted
Water surrounds the cartilage and is squeezed out and goes back in with compression. It absorbs the shock
What are GLYCOPROTEINS?
mostly protein, oligosaccharide chain is covalently attached
O-linked or N-linked
Oligosaccharides are used
Sialic acid is very common component of Glycoproteins
Fucose
Dolichol is used to attach carbohydrate to protein as the protein is being synthesized in the rER (N-linked)
Where does most of the processing of a Glycoprotein occur?
in the ER
some occurs in the Golgi
what are the functions of Glycoproteins?
structural: collagens
lubricants: mucins
Transport: transferrin
Immune: immunoglobins, blood group determinants
Hormone & cytokine: HCG & TSH
Enzyme: alkalline phosphatase
Blood clotting: fibrinogen
Cell surface recognition: Lectins
compare and contrast proteoglycans vs. glycoproteins.
Proteoglycans:
1. mostly carbohydrate
2. GAGs
3. O-linked to serine
4. NO SIALIC acid
5. Xylose (attached to serine)
Glycoproteins
1. Mostly protein
2. Oligosaccharides
3. O-linked (serine, threonine, hydroxylysine)
4. N-linked (Asparagine)
5. Sialic acid
6. Fucose
7. Dolichol (N-linked)
what is SELECTIN?
an animal glycoprotein (animal lectins)
-lectins are sugar binding proteins
Are all lectins glycoproteins?
NO
How many types of Lectins are present in humans?
3
what is an L-selectin ?
produced by WBCs and allows them to attach to blood vessels and then enter the tissues
-first step of plaque formation
what are P-selectins?
produced by platelets and allows them to aggregate on endothelial cells to start blood clot formation process. Recruits WBCs
-always being made
what are E-selectins?
helps recruit WBCs to the site of injury
-have to be made: the gene coding for it has to be turned on
What is Integrin?
selectins allow WBCs to tether and roll along the wall of blood vessels but integrin holds them so that they can move into the intima
-FUCOSE is an important component of the oligosaccharides that are used to form the 24 different integrins
what is an important component of the oligosaccharides used to form integrins?
FUCOSE
What is RICIN?
Ricin is one of the deadliest toxins known to man
Ricin inhibits protein synthesis is cells
how does Ricin inhibit Protein synthesis in cells?
inhibits the binding of elongation factor 2 to the 28S ribosome which inhibits protein synthesis
what is the mortality rate related to ricin ingestion?
85%
what do people consume that has ricin in it?
raw Castro beans
how does cooking castro beans make them safe to eat?
heating the ricin denatures it and destroys it's toxicity