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In what 2 diseases does heparan and dermatan sulfate accumulate?
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What enzyme is deficient in Hurlers disease?
alpha L iduronidase
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What enzyme is deficient in Hunter's syndrome?
Iduronate sulfatase
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Which enzyme is deficient in I cell disease?
GlcNac phosphotransferase
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are glycoproteins or proteoglycans branched?
- glycoproteins branched
- proteoglycans --unbranched
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Enzymes destined for lysosomes are tagged how?
- Mannose 6 phosphate.
- Mannose in ER
- Phosphylation in Golgi Aparatus
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O linked glycosidic bonds use what a.a?
serine, threonine, hydroxylysine
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N linked glycosidic bonds use what a.a?
Asparagine
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What is the major feature of complex class of oligosaccharides linked to a protein in glycoproteins?
Sialic Acid
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O linked carbs are attached in glycoproteins are attached where?
GA
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N linked carbs are attached where?
What is needed?
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In glycoproteins the following consensus sequence is attached to a protein: Asn-x-ser/Threonine
X can be any a.a except?
Proline
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NANA(sialic acid) is incorporated into a glycoprotein using what high energy molecule
CMP-NANA
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In O glycosidic linked carbs what sugar is used
galactose
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In N linked glycosidic linked carbs, what sugar is used?
glucose
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Which is more common, N or O linked?
N linked
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Which one of the glucosaminoglycans is not sulfated and covalently linked to proteins?
Hyaluronic acid
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What the function of Hyaluronic acid?
- shock absorber
- lubricant
- found in synovial fluid, vitreous humor, extracellular matrix
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Which one of the GAGs does not have uronic acid?
Keratan sulfate
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Where is Dermatan sulfate found?
- Skin
- Blood vessels
- Heart Valves
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Chondroitin sulfates are found where?
cartilage, tendons
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What is the only intracellular GAG
Heparin
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What is the trisaccharide linkage in proteoglycans?
gal-gal-xylose-serine
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Why are the core proteins of proteoglycans rich in serine and threonine residues??
So that O linkages to carbs can occur
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How are proteoglycan monomers held onto Hyaluronic acid?
ionic interactions
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What is the source of sulfate for proteoglycans?
paps
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L gulonate to ascorbate requires what acid that is absent in humans?
L gulono lactone oxidase
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Sulfation and acetylation of proteoglycans occurs when?
after monosaccharides have been incorporated
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What property of GAG explains their reaction?
they are negatively charged
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What is the repeating disaccharide in a GAG?
Amino sugar-acidic sugar
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Proteoglycans bind to what GAG?
Hyularonic acid
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Which gag does not have Uronic acid?
Keratan sulfate
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What takes place of uronic acid in Keratan sulfate?
Galactose
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Are GAGs hetero or homo polysaccharides?
heteropolysaccharides
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What are the repeating disaccharides units in GAGs?
D-gluco or galactosamine and D- Gluco or galactoronic acid(Uronic acid)
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Which is the GAG that has L sugars and and a variety of other sugars such as NANA?
Keratan sulfate
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What makes up the trihexoside linker protein?
Gal-Gal-Xylose-serine
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In I cell disease what is not phosphorylated?
Mannose viA THE deficient enzyme GlcNac phosphotransferase
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What is the relation between insulin and potassium?
Insulin sequesters potassium in cells
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How is Hyperkalemia treated?
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What leads to polyphagia in DM?
- Lack of insulin prevents entry of glucose into satiety center
- lack of entry of glucose disinhibits hunger center
- hunger amongst plenty
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