Unit 2 Section 5.3 Antibodies

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  • Antibodies
    • Antibody structure
      • antibodies are proteins - they're made up of chains of amino acid monomers linked by peptide bonds
      • The variable regions of the antibody form the antigen binding sites
      • The shape of the variable region is complementary to a particular antigen
      • the variable regions differ between antibodies
      • The hinge region allows flexibility when the antibody binds to the antigen
      • The constant regions allow binding to receptors on immune system cells
      • the constant region is the same in all antibodies
      • Disulfide bridges hold the polypeptide chains together
    • The role of antibodies in clearing infections
      • antibodies help to clear an infection in three main ways
      • 1. Agglutinating pathogens
        • each antibody has two binding sites, so an anyibody can bind to two pathogens at a time. the pathogens become clumped together. Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once
      • 2. Neutralising toxins
        • antibodies can bind to the toxins produced by pathogens. this prevents the toxins from affecting human cells, so the toxins are neutralised. the toxin antibody complexes are also phagocytosed
      • 3. Preventing the pathogen binding the human cells
        • when antibodies bind to the antigens on the pathogens they may block the cell surface receptors that the pathogens need to bind to the host cells. this means the pathogen can't attach to or infect the host cells


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