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Glycoprotein

QuestionAnswer
Sugars must be activated before transfer reactions can occur (T/F) True
Describe the importance of UDP-glucuronate and glucuronyl transfer reactions in the elimination of bilirubin, steroids and other small molecules -Addition of UDP-Glucoronate adds a negative charge -This makes hydrophobic molecules water soluble allowing them to be excreted -Occurs in the liver, catalyzed by glucuronyltransferase (of which there are several isoforms with different specificities
Compare Gilbert’s syndrome with Crigler-Najjar syndrome Crigler-Najjar syndrome: -Severely impaired or absent glucronyltransferase activity -Uncommon -Severity depends on how much activity remains -Type I, severe defect leads to kernicterus & death if untreated -Type II, less severe defect
Compare Gilbert’s syndrome with Crigler-Najjar syndrome Gilbert's syndrome: -Mildly reduced expression of glucuronyltransferase -Very Common (estimated 3-7% of US Pop.) -Results in slightly elevated bilirubin levels but no detrimental health effects -May have increased sensitivity to certain drugs
Briefly describe the process of lactose synthesis and where it occurs UDP-Glucose--->UDP-Galactose + Glucose--->Lactose (enzyme: Lactose Synthase) UDP-Glucose<---UDP-Galactose (enzyme: epimerase) -Occurs only in the lactating mammary gland -Regulated by prolactin
Compare and contrast the synthesis and degradation of proteoglycans, glycoproteins and glycolipids Proteoglycans: -Their synthesis is very complex -Turn over by shedding from the cell surface and by endocytosis (broken down in lysozomes) -Can be extracellular or attached to the membrane
Compare and contrast the synthesis and degradation of proteoglycans, glycoproteins and glycolipids Glycoproteins: -Very complex synthetic pathway where N-linked (usually to Asp) or O-linked (usually Ser or Thr) glycosidic bonds -Glycoproteins get phosphorylated on mannose residues -This is a signal targeting them to the lysosomes
Compare and contrast the synthesis and degradation of proteoglycans, glycoproteins, and glycolipids Glycolipids: -nearly all are derived from ceramide and are called glycosphingolipids -are endocytosed and degraded in lysosomes in a multistep process involving many enzymes -
Explain the difference between glycosaminoglycans, proteoglycans and glycoproteins GAGs: -are long heteropolysaccharide chains with lots of negative charge -Because of the charge they repel one another and attract water -Very complex synthesis -Almost all GAGs are covalently attached to a core protein so they are called proteoglycan
Explain the difference between glycosaminoglycans, proteoglycans and glycoproteins Glycoproteins: -More protein, less carbohydrate -The carb components tend to be shorter than those of proteoglycans, have less charge and are branched -Are often secreted or are present on the cell's surface
Describe the process that targets proteins to the lysosome and the role of mannose phosphorylation The glycoprotein becomes phosphorylated on mannose residues. This signal targeting them to the lysosomes -Mannose phosphorylation is a special process that targets glycoproteins to lysosomes
Define I-cell disease a disease that results when there is a deficiency in the enzyme that phosporylates mannose residues -Lysosomal enzymes get secreted -lysosomes don't have the full complement of required enzymes so proteins build up in them (inclusions) -Extremely rare
Distinguish between, glucocerebrosides, galactocerebrosides and gangliosides Glucocerebroside: Ceramide + UDP-Glucose Galactocerebrosides: Ceramide + UDP-Galactose Ganglioside: Ceramide + 2 or more UDP-sugars and N-acetylneuraminic acid (NANA)
What is Hunter Syndrome? X-linked chromosome syndrome of mucopolysaccharidoses -All mucopolysaccharidoses are autosomal recessive except Hunter Syndrome
The carbohydrate components of sugars and lipids can be antigenic (T/F)and explain their role in blood type True, glycolipids on RBC membranes are determinants of blood type
Fabry Disease X-linked disease
Explain the role of lysosomes in degradation of proteoglycans, glycoproteins and glycolipids Breaks down proteins
Define the term “lysosomal storage disease” A deficiency in one of these enzymes leads to accumulation of sphingolipids, glycoproteins, and GAGs (mucopolysaccharides)
Distinguish between sphingolipidoses, glycoproteinoses and mucopolysaccharidoses Sphingolipidoses- disorders relating to sphingolipid metab. Glycoproteinoses- absence or malfunctioning of lysosomal enzymes needed to breakdown glycoproteins mucopolysaccharidoses- absence or malfunctioning of lysosomal enzymes needed to breakdown GAGs
Explain the general etiology of these diseases (Fabry disease, Gaucher disease, Tav-Sachs disease, Neimann-Pick disease, others) Not specifics, just know that degradation occurs in the lysosomes, is a multistep process and that various degradation products can build up depending on where the deficiency is
Hunter Syndrome is an X-linked mucopolysaccharidosis (T/F) True
Fabry disease, Tay-Sachs disease, Gaucher disease and Neimann-Pick disease are sphingolipidoses and that Fabry disease is X-linked (T/F) True
What are mucopolysaccharidoses -deficiency of enzymes that breakdown GAG fragments, thus they accumulate in the lysosomes -can cause a variety of problems such as skeletal deformities and mental retardation -Mucopolysaccharides will be found in the urine -depends which enzyme's abse
What is sphingolipidosis? a deficiency in an enzyme that results in an accumulation of sphingolipids in the lysosomes -Fabry disease is x-linked, others are autosomal recessive
Created by: jgrayson
 

 



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