Antibodies

• What do antibodies bind to?

  Antigens
• What is formed when antibodies bind to antigens?

  An antigen-antibody complex
• What type of protein structure do anitbodies have?

  Quaternary - because they are made up of more than one polypeptide chain joined together
• How many polypeptide chains are in an antibody?

  Four polypeptide chains
• What are the two types of chains in an antibody?

  Heavy and light chains
• What connects the polypeptide chains in an antibody?

  Disulphide bridges
• What is the function of the constant region in an antibody?

  Allows binding to receptors on immune system cells e.g phagocytes
• What is the function of the variable region in an antibody?

  The antigen binding site, complementary to a specific antigen
• How many pathogens can one antibody bind to at a time?

  Two pathogens
• What is agglutination?


  Antibodies join and clump pathogens together
• How does agglutination help the immune response?

  Makes it easier for phagocytes to engulf multiple pathogens
• How do antibodies neutralise toxins?


  By binding to them and reducing their effects
• How do antibodies prevent viruses from entering host cells?

  By binding to proteins on viruses and preventing attachment
• What is the role of spike proteins on viruses?


  They bind to proteins on the surface of the virus that allow viruses to enter cells
• What is antigenic variability?

  When pathogens have strains with different antigens
• Why does antigenic variation prevent memory cells from being effective?


  Memory cells won't recognise the antigen and won't be activated
• Why won't memory cells recognise a pathogen with different antigens?

  Because the antigens have changed due to mutations
• What makes antibodies specific to antigens?

  Their unique variable region is complementary to a specific antigen
• What happens if a pathogen has antigenic variation?

  The body has to start again with the primary response
• Why does the primary response occur with antigenic variation?

  Because the antibodies from the previous infection are no longer complementary
• Why is it difficult to produce vaccines for diseases with antigenic variation?

  Because of the constant changes in antigens
• What must be done each year for the flu vaccine due to antigenic variation?

  A new vaccine is made based on the most recent strain
• What type of proteins are antibodies?

  Globular proteins
• What are antibodies made up of?

  4 polypeptide chains -> chains of one pair are longer (heavy chains) and chains of the other pair are shorter (light chains)

  Variable region -> made up of the antigen binding site

  Constant region -> Made up of heavy chains and disulphide bonds

  
• What is the difference between the constant region and variable region?

  Constant region is the same for all antibodies whereas the variable region is different for different antibodies (as there is a different amino acid sequence)