AQA A Level Biology复习笔记2.5.9 Antigen-Antibody Complex

Antigen-Antibody Complex

 

  • An antigen and its complementary antibody have complementary molecular shapes
    • This means that their molecular structures fit into each other

     

  • When an antibody collides (randomly) with a foreign cell that possesses non-self antigens with a complementary shape, it binds with one of the antigens
  • When this occurs, the two molecules combine to form an antigen-antibody complex

Antigen-antibody-complex

A diagrammatic version of an antigen-antibody complex showing the basic features (in reality, both antigens and antibodies have highly complex 3D structures)

 

  • As seen in the diagram above, antibodies have at least two antigen-binding sites
  • This means they can bind to more than one bacterium or virus at the same time
  • This cause groups of the same pathogens to become clumped together
    • This process is known as agglutination

     

  • The binding of antibodies to the antigens either neutralises the pathogen or acts like a marker to attract phagocytes to engulf and destroy the pathogens
    • Due to agglutination, phagocytes can often phagocytose many pathogens at the same time, as they are all clumped together

     

Agglutinated-pathogens-cannot-move-easily

Agglutinated pathogens cannot move easily, so they are easily engulfed and destroyed by phagocytes

 

Exam Tip

Remember - antibodies can cause pathogens to stick together (due to their multiple antigen-binding sites), a bit like glue. This might help you remember the biological name for this process: agglutination!

 

转载自savemyexams

更多Alevel课程
翰林国际教育资讯二维码