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Glycoprotein
| Question | Answer |
|---|---|
| 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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