Immunity

• Physical and chemical barriers


  Stop pathogens from getting into the body
• Immune system


  Destroys pathogens that do make it into the body
• Skin


  • Acts as a physical barrier that pathogens can't get through
  • Secretes oils and antimicrobial substances that can kill pathogens
• Nose


  Has hairs and mucus that trap pathogens and particles in the air
• Trachea and esophagus


  Only two tubes leaving the throat that pathogens can enter
• Trachea, bronchi, and bronchioles


  1. Covered in mucus that traps particles

  2. Lined with cilia that move mucus and trapped particles up to the throat to be swallowed
• Stomach acid


  Hydrochloric acid that kills most pathogens
• White blood cells


  • Most important part of the immune system
  • Continually patrol the body
  • Have three main functions: phagocytosis, producing antitoxins, and producing antibodies
• Phagocytosis


  Process where white blood cells consume and destroy pathogens
• Antitoxins


  Molecules produced by white blood cells that bind and counteract toxins produced by pathogens
• Antigens


  Substances detected by the immune system as foreign, such as bacterial cell walls or viral proteins
• Antibodies


  Proteins made by white blood cells that can bind to specific antigens and signal for their destruction
• Immune system remembers pathogens


  Produces many antibodies quickly to destroy pathogens before they can develop
• The body survives millions of pathogens attacking it every day
• Lytic cycle steps 


  1.Virus attaches to a host cell.

  2.Virus injects genetic material into the host cell.

  3.The cell machinery of the host cell produces viral components.

  4.New viruses are assembled from the replicated components.

  5.The host cell bursts, releasing new viruses - which go on to infect other cells and repeat the cycle.
• lysogenic cycle steps


  1.Virus attaches to a host cell.

  2.Virus injects genetic material into the host cell.

  3.Viral DNA incorporates into the host cell's genome. Virus remains dormant, and does not cause immediate harm

  4.The host cell divides, replicating the viral DNA (contained within the host's genome) into each daughter cell.

  5.Environmental triggers can cause a switch to the lytic cycle, and the viral DNA exits the host's genome

  6.The lytic pathway starts - the host cell's machinery beings to produce viral components.