Glycoprotein
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Questions and Answers

Where does O-linked glycosylation take place?

  • Nucleus
  • Golgi apparatus (correct)
  • Mitochondria
  • Endoplasmic reticulum

    • What type of glycosylation has oligosaccharide chains attached to the amino group of asparagine residues?

  • O-linked glycosylation
  • N-Glycosylation (correct)
  • P-Glycosylation
  • C-Glycosylation

    • Which type of glycosylation influences protein folding, cellular trafficking, and recognition?

  • N-Glycosylation (correct)
  • P-Glycosylation
  • O-linked glycosylation
  • C-Glycosylation

    • What is the function of Glypiation?

    <p>Links proteins to lipids through glycan linkages</p> Signup and view all the answers

    Which enzyme deficiency results in I-Cell Disease?

    <p>UDP NAcGlc phosphotransferase</p> Signup and view all the answers

    What is the carrier rate of I-Cell Disease in NE Quebec?

    <p>1/150</p> Signup and view all the answers

    Which type of mucolipidosis is caused by a defect in the protein recognition domain of UDP-NAcGlcN phosphotransferase?

    <p>Pseudo-Hurler Disease</p> Signup and view all the answers

    What is the incidence of Type II Mucolipidosis in Portugal?

    <p>1:125,000</p> Signup and view all the answers

    Which enzyme deficiency results in Hunter syndrome?

    Signup and view all the answers

    What are the clinical presentations of I-Cell Disease?

    <p>All of the above</p> Signup and view all the answers

    What is the inheritance pattern of Hunter syndrome?

    <p>X-linked recessive</p> Signup and view all the answers

    What is the difference between Type II Mucolipidosis and Pseudo-Hurler Disease?

    <p>Severity of symptoms</p> Signup and view all the answers

    Which lysosomal storage disease results in the buildup of glycosaminoglycans due to a deficiency of alpha-L iduronidase?

    <p>Hurler syndrome</p> Signup and view all the answers

    What is the characteristic feature of Pseudo-Hurler Disease?

    <p>Normal intelligence</p> Signup and view all the answers

    What is the function of glycan chains in glycoproteins?

    <p>Folding and solubility</p> Signup and view all the answers

    What is the main cause of death in patients with Hurler syndrome?

    <p>Organ damage</p> Signup and view all the answers

    Which glycoprotein hormone is primarily produced in adult kidneys, promoting red cell production?

    <p>EPO</p> Signup and view all the answers

    Which glycoprotein allows survival in sub-zero temperatures for certain species like arctic fish and snow fleas?

    <p>AFGPs</p> Signup and view all the answers

    Where is the glycosylation section of most glycoproteins located?

    <p>Extracellular part of the protein</p> Signup and view all the answers

    Which protein is a major sialoglycoprotein on the surface of human immune cells?

    <p>Transcript Leukosialin</p> Signup and view all the answers

    What is the first sugar transferred to Ser or Thr residues of protein by GalNAc or GlcNAc transferase in Golgi?

    <p>GalNAc or GlcNAc</p> Signup and view all the answers

    Which protein interferes with the formation of complement convertases on the cell surface?

    <p>Decay-accelerating factor (DAF)</p> Signup and view all the answers

    Which glycoprotein is modified by a disaccharide on hydroxylysine residues?

    <p>Collagen</p> Signup and view all the answers

    Which glycoprotein is a protective barrier and provides lubrication in mucus?

    <p>Mucin</p> Signup and view all the answers

    Where is the biosynthesis of O-linked glycoproteins primarily carried out?

    <p>Endoplasmic reticulum (ER) and Golgi apparatus</p> Signup and view all the answers

    What is the primary function of AFP, alpha-fetoprotein?

    <p>Produced during gestation and by degenerating tissues in malignancy</p> Signup and view all the answers

    Which glycoprotein is part of the glycoprotein hormone family that includes LH, FSH, and hCG?

    <p>TSH</p> Signup and view all the answers

    Which sugar derivative is the first to be transferred to Ser or Thr residues of protein by GalNAc or GlcNAc transferase in Golgi?

    <p>GalNAc or GlcNAc</p> Signup and view all the answers

    Which type of linkage can glycans have with a protein?

    <p>O-linked</p> Signup and view all the answers

    What are some examples of unusual sugars found in sugar chains of glycoproteins?

    <p>L-fucose, D-xylose, D-mannose</p> Signup and view all the answers

    Which monosaccharides are important in glycoproteins and have unique biological roles?

    <p>Glucosamine, N-acetylgalactosamine, sialic acid</p> Signup and view all the answers

    Where can protein-linked glycans be attached to the Myo-inositol ring?

    <p>Via an ethanolamine phosphate</p> Signup and view all the answers

    What are the types of oligosaccharide chains that proteins can have?

    <p>O-linked and N-linked</p> Signup and view all the answers

    What crucial roles do glycoproteins play in?

    <p>Cell surface recognition and immune responses</p> Signup and view all the answers

    What do the carbohydrate moieties of glycoproteins enable?

    <p>Cell-to-cell recognition and immune responses</p> Signup and view all the answers

    What do glycoproteins determine?

    <p>Blood group antigens and tissue compatibility</p> Signup and view all the answers

    What role do glycoproteins play in the extracellular matrix?

    <p>Cell adhesion and tissue regeneration</p> Signup and view all the answers

    What functions do mucins, heavily glycosylated proteins, provide?

    <p>Lubrication and protection against pathogens</p> Signup and view all the answers

    What role does the major histocompatibility complex (MHC) play?

    <p>Immune system recognition of foreign molecules</p> Signup and view all the answers

    What is the function of lectins, sugar-binding proteins?

    <p>Facilitate cell-cell interaction and bind to cell membranes</p> Signup and view all the answers

    Which glycoprotein is part of the glycoprotein hormone family that includes LH, FSH, and hCG?

    <p>Alpha-fetoprotein (AFP)</p> Signup and view all the answers

    What is the function of lectins, sugar-binding proteins?

    <p>Mediate carbohydrate-dependent cell-cell interaction in inflammation</p> Signup and view all the answers

    Where is the biosynthesis of O-linked glycoproteins primarily carried out?

    <p>Golgi complex</p> Signup and view all the answers

    What is the primary function of AFP, alpha-fetoprotein?

    <p>Promote red cell production</p> Signup and view all the answers

    What is the inheritance pattern of I-Cell Disease?

    <p>Autosomal recessive</p> Signup and view all the answers

    What enzyme deficiency results in Hunter syndrome?

    <p>Alpha-L iduronidase</p> Signup and view all the answers

    What is the characteristic feature of Pseudo-Hurler Disease?

    <p>Severe growth retardation</p> Signup and view all the answers

    What do the carbohydrate moieties of glycoproteins enable?

    <p>All of the above</p> Signup and view all the answers

    What are the clinical presentations of I-Cell Disease?

    <p>All of the above</p> Signup and view all the answers

    Which enzyme deficiency results in I-Cell Disease?

    <p>N-acetylglucosaminyl-1-phosphotransferase</p> Signup and view all the answers

    Where can protein-linked glycans be attached to the Myo-inositol ring?

    <p>C-terminus</p> Signup and view all the answers

    What is the function of Glypiation?

    <p>Anchor the protein to the cell membrane</p> Signup and view all the answers

    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.

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