Antibody (Ig) Structure and Function
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Questions and Answers

What is the molecular weight of the Fab portion of the Ig?

  • 7S
  • 19S
  • 11S
  • 45 kDa (correct)

    • What is the main characteristic feature provided by the Fc portion of the immunoglobulins?

  • Combination with the antigenic determinant (Epitope)
  • Crystallization into pure protein crystals (correct)
  • Variability in the position of amino acids
  • Flexibility to bind two antigenic sites at the same time

    • Which immunoglobulin has the heaviest molecular weight according to Svedberg's unit?

  • IgA
  • IgM (correct)
  • IgG
  • IgE

    • What is the function of the paratope in the Fab portion of the antibody?

    <p>Combines with the antigenic determinant (Epitope)</p> Signup and view all the answers

    What are the hypervariable areas in the variable portion of Ig called?

    <p>Complementarity determining region (CDR)</p> Signup and view all the answers

    What holds together the 4 polypeptide chains in an Ig molecule?

    <p>-S-S- disulfide bond</p> Signup and view all the answers

    What is the main source of synthesis for γ-globulin?

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

    How many polypeptide chains make up an Immunoglobulin (Ig) molecule?

    <p>4</p> Signup and view all the answers

    In an Ig molecule, how many types of light chains can be present on both arms?

    <p>Kappa and lambda</p> Signup and view all the answers

    What is the basis for classifying Ig into different types?

    <p>Molecular weight, sedimentation coefficient, and carbohydrate contents</p> Signup and view all the answers

    What is the primary function of the paratope in an antibody?

    <p>To bind to antigens</p> Signup and view all the answers

    Which type of gamma globulin primarily provides passive immunity to newborns?

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

    What is the main source of synthesis for IgA antibodies?

    <p>Plasma cells in mucosal tissues</p> Signup and view all the answers

    Which region of an antibody molecule determines its class (e.g., IgM, IgG, IgA, etc.)?

    <p>Constant region</p> Signup and view all the answers

    What is the main characteristic feature provided by the Fc portion of immunoglobulins?

    <p>Complement activation</p> Signup and view all the answers

    In an IgM molecule, how many antigen-binding sites are present?

    <p>4</p> Signup and view all the answers

    What is the etiology of syphilis?

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

    Which disease is characterized by the presence of Shigella bacteria?

    <p>Food poisoning</p> Signup and view all the answers

    What is the pathophysiology of erythroblastosis fetalis?

    <p>Immune response to fetal red blood cells</p> Signup and view all the answers

    What is the main focus of the laboratory diagnosis of PUO?

    <p>Diagnosing persistent fever of unknown origin</p> Signup and view all the answers

    Study Notes

    Immunoglobulin Structure and Function

    • The molecular weight of the Fab portion of the Ig is not specified in the text, but it can be mentioned that Fab is the antigen-binding fragment of an antibody.
    • The Fc portion of immunoglobulins provides the main characteristic feature of activating the complement system and binding to Fc receptors.

    Immunoglobulin Types

    • IgM has the heaviest molecular weight according to Svedberg's unit.
    • The basis for classifying Ig into different types is based on the amino acid sequence of the heavy chain constant region, which determines the class (e.g., IgM, IgG, IgA, etc.).

    Antibody Function

    • The paratope is the region in the Fab portion of the antibody that recognizes and binds to the specific epitope of the antigen, providing the primary function of recognizing and binding to specific antigens.

    Immunoglobulin Structure

    • The four polypeptide chains in an Ig molecule are held together by disulfide bonds and non-covalent interactions.
    • Each Ig molecule consists of two heavy chains and two light chains, with two types of light chains (κ or λ) that can be present on both arms.
    • The main source of synthesis for γ-globulin is plasma cells.

    Passive Immunity and IgA Synthesis

    • IgG provides passive immunity to newborns.
    • The main source of synthesis for IgA antibodies is mucosal tissues, such as those found in the gut and respiratory tract.

    Laboratory Diagnosis

    • The main focus of the laboratory diagnosis of PUO (pyrexia of unknown origin) is not specified in the text.
    • Shigella bacteria are the causative agents of bacillary dysentery.
    • The etiology of syphilis is not specified in the text, but it is caused by the bacterium Treponema pallidum.
    • Erythroblastosis fetalis is a hemolytic disease of the newborn, caused by maternal-fetal incompatibility of the Rh blood group.

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    Description

    Test your knowledge about the structure and function of antibodies (Ig) based on the detailed description provided by Porter and Edelman in 1950. Explore the synthesis of γ-globulin by the liver, production by immune cells, and the Nobel Prize-winning contributions to the understanding of immunoglobulins.

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