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Questions and Answers
Where does O-linked glycosylation take place?
What type of glycosylation has oligosaccharide chains attached to the amino group of asparagine residues?
Which type of glycosylation influences protein folding, cellular trafficking, and recognition?
What is the function of Glypiation?
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Which enzyme deficiency results in I-Cell Disease?
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What is the carrier rate of I-Cell Disease in NE Quebec?
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Which type of mucolipidosis is caused by a defect in the protein recognition domain of UDP-NAcGlcN phosphotransferase?
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What is the incidence of Type II Mucolipidosis in Portugal?
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Which enzyme deficiency results in Hunter syndrome?
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What are the clinical presentations of I-Cell Disease?
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What is the inheritance pattern of Hunter syndrome?
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What is the difference between Type II Mucolipidosis and Pseudo-Hurler Disease?
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Which lysosomal storage disease results in the buildup of glycosaminoglycans due to a deficiency of alpha-L iduronidase?
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What is the characteristic feature of Pseudo-Hurler Disease?
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What is the function of glycan chains in glycoproteins?
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What is the main cause of death in patients with Hurler syndrome?
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Which glycoprotein hormone is primarily produced in adult kidneys, promoting red cell production?
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Which glycoprotein allows survival in sub-zero temperatures for certain species like arctic fish and snow fleas?
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Where is the glycosylation section of most glycoproteins located?
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Which protein is a major sialoglycoprotein on the surface of human immune cells?
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What is the first sugar transferred to Ser or Thr residues of protein by GalNAc or GlcNAc transferase in Golgi?
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Which protein interferes with the formation of complement convertases on the cell surface?
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Which glycoprotein is modified by a disaccharide on hydroxylysine residues?
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Which glycoprotein is a protective barrier and provides lubrication in mucus?
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Where is the biosynthesis of O-linked glycoproteins primarily carried out?
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What is the primary function of AFP, alpha-fetoprotein?
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Which glycoprotein is part of the glycoprotein hormone family that includes LH, FSH, and hCG?
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Which sugar derivative is the first to be transferred to Ser or Thr residues of protein by GalNAc or GlcNAc transferase in Golgi?
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Which type of linkage can glycans have with a protein?
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What are some examples of unusual sugars found in sugar chains of glycoproteins?
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Which monosaccharides are important in glycoproteins and have unique biological roles?
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Where can protein-linked glycans be attached to the Myo-inositol ring?
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What are the types of oligosaccharide chains that proteins can have?
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What crucial roles do glycoproteins play in?
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What do the carbohydrate moieties of glycoproteins enable?
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What do glycoproteins determine?
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What role do glycoproteins play in the extracellular matrix?
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What functions do mucins, heavily glycosylated proteins, provide?
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What role does the major histocompatibility complex (MHC) play?
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What is the function of lectins, sugar-binding proteins?
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Which glycoprotein is part of the glycoprotein hormone family that includes LH, FSH, and hCG?
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What is the function of lectins, sugar-binding proteins?
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Where is the biosynthesis of O-linked glycoproteins primarily carried out?
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What is the primary function of AFP, alpha-fetoprotein?
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What is the inheritance pattern of I-Cell Disease?
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What enzyme deficiency results in Hunter syndrome?
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What is the characteristic feature of Pseudo-Hurler Disease?
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What do the carbohydrate moieties of glycoproteins enable?
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What are the clinical presentations of I-Cell Disease?
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Which enzyme deficiency results in I-Cell Disease?
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Where can protein-linked glycans be attached to the Myo-inositol ring?
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What is the function of Glypiation?
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Study Notes
Glycoprotein Structure and Functions
- Glycans can be linked to the C-terminal of a protein or to the Myo-inositol ring of a membrane phospholipid via an ethanolamine phosphate.
- Sugar chains in glycoproteins are often branched and contain unusual sugars like L-fucose, D-xylose, D-mannose, and D-amino sugars.
- Unusual aldoses, including aldotetroses, aldopentoses, and aldohexoses, are present in glycoproteins.
- Important monosaccharides in glycoproteins include glucosamine, N-acetylgalactosamine, and sialic acid, each with unique biological roles.
- Proteins can have both O-linked and N-linked oligosaccharide chains, such as the low-density lipoprotein (LDL) receptor.
- Glycoproteins play crucial roles in cell surface recognition, cell surface antigenicity, extracellular matrix formation, and mucin production.
- The carbohydrate moieties of glycoproteins enable cell-to-cell recognition, immune responses, and tissue development.
- Glycoproteins determine blood group antigens and are essential for blood transfusion compatibility.
- Glycoproteins are fundamental in the extracellular matrix, facilitating cell adhesion, migration, and tissue regeneration.
- Mucins, heavily glycosylated proteins, provide lubrication, protection against pathogens, and serve as a barrier between tissues and the external environment.
- The major histocompatibility complex (MHC) plays a crucial role in the acquired immune system's recognition of foreign molecules.
- Lectins, sugar-binding proteins, facilitate cell-cell interaction and can bind to cell membranes without involving the immune system.
Biosynthesis of N-linked Glycoproteins and Lipid Anchors
- Glycosylphosphatidylinositol (GPI) is a glycolipid attached to a protein's C-terminus during posttranslational modification, playing crucial roles in various biological processes.
- GPI is composed of a phosphatidylinositol group linked through a carbohydrate-containing linker and an ethanolamine phosphate bridge to the protein's C-terminal amino acid, anchoring the protein to the cell membrane.
- Dolichol phosphate, a lipid molecule found in the ER membrane, acts as a lipid anchor for growing carbohydrate chains and can be inhibited by statins.
- Dolichol phosphate, attached to a protein's asparagine through a pyrophosphate linkage, undergoes sequential addition of n-acetylglucosamine, mannose, and glucose via glycosyltransferases, different from O-linked glycoproteins.
- Dolichol serves as a marker of aging status, with levels of dolichol, ubiquinone, and cholesterol showing variations in different age groups and diseases such as Alzheimer's.
- Polyprenoid compounds derived from conifer needles have multifaceted treatment uses, including liver disease, neurological, GI, colds, flu, Alzheimer's, alcoholism, drug addiction, and depression.
- N-linked and O-linked glycoproteins are targeted to their destination by specific amino acid sequences, with N-terminal hydrophobic sequence directing proteins to the ER during synthesis, and the Golgi complex sorting based on glycoprotein A.
- N-linked glycoproteins, more common than O-linked, contain a common core of three mannose residues and two GlcNAc attached to the polypeptide, with asparagine at the site of glycosylation in an -Asn-X-Ser(Thr)- consensus sequence.
- N-linked oligosaccharide families include high-mannose, hybrid, and complex types, each with distinct sugar compositions and common in various organisms.
- Glycans in glycoproteins are involved in protein folding, solubility, stability, cell-cell interactions, carbohydrate-dependent cell-cell interaction in inflammation, lectin-carbohydrate interactions, and ABO blood group antigens.
- I-cell disease, caused by mutations in the GNPTAB gene, is a severe genetic disorder falling under lysosomal storage diseases, leading to various symptoms such as skeletal abnormalities, organ dysfunction, and intellectual disability, with no known cure.
- I-cell disease management primarily focuses on symptom management, physical therapy, pain management, and supportive care, requiring specialized medical attention and ongoing care from a team of healthcare professionals.
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Description
Test your knowledge of glycoprotein structure and functions, as well as the biosynthesis of N-linked glycoproteins and lipid anchors with this informative quiz. Explore topics such as sugar chains, protein linkage, biological roles, and genetic disorders related to glycoproteins.
