immune response

• lymphocyte 


  identifies non-self cells
• what type of cells do lymphocytes identify

  -abnormal cells

  -toxins

  -pathogens

  -cells from other organisms of the same species
• what is produced when non-self cells are identified

  an immune response
• antigen


  a protein in the cell surface membrane that triggers an immune response
• what are antigens used to do

  used by lymphocytes to help identify non-self cells
• what do lymphocytes have on their surface

  antigen receptors
• how do lymphocytes and antigens produce a specific immune response

  lymphocytes have antigen receptors which are complimentary to a particular antigen which they bind to and trigger a specific immune response
• phagocyte 


  identifies non-self cells
• what cells do phagocytes identify

  pathogens
• why can phagocytes identify pathogens

  each pathogen has a particular pattern of molecules on its cell surface and each phagocyte has receptors complimentary to these patterns
• what type of response to phagocytes trigger

  non specific immune response
• what type of response to lymphocytes trigger

  specific immune response
• what is phagocytosis 


  when a phagocyte engulfs a pathogen and breaks it down from the inside
• explain the first step of phagocytosis

  pathogen releases chemicals which attracts the phagocyte towards it down a concentration gradient
• explain the second step of phagocytosis

  phagocyte binds to the pathogen via receptors which are complimentary to the patterns on the pathogen
• explain the third step of phagocytosis

  the phagocyte engulfs the pathogen, encasing it in a vesicle, structure is called a phagosome
• explain the fourth step of phagocytosis

  lysosomes in the phagocyte move towards and fuse with the phagosome
• explain the fifth step of phagocytosis

  lysozymes are released by the lysosomes into the phagosome which hydrolyse the pathogen
• explain the sixth step of phagocytosis

  any soluble structures are absorbed into the cytoplasm and all else is expelled from the phagosome
• phagocytosis exam question answer

  The phagocyte is attracted to chemicals released by the pathogen and moves down a concentration gradient. Receptors on the phagocyte bind to the pathogen. The phagocyte engulfs the pathogen to form a phagosome. Lysosomes in the phagocyte fuse with the phagosome. The lysosomes release lysozymes which hydrolyse the pathogen. The cytoplasm absorbs the soluble products of this reaction.