Biology 1 - Fighting Disease

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Fighting Disease 

  • Microorganisms that enter the body and cause disease are called pathogens which cause infectious diseases.
  • The 2 types of main pathogens are bacteria and viruses.


  • Bacteria are very small cells which can reproduce inside your body very quickly.
  • They make you feel ill by damaging your celsls and producing toxins.


  • Viruses are not cells and are very very small (smaller than Bacteria.)
  • They replicate themselves by invading your cells' and using their machinery to replicate themselves. 
  • The cell will then burst releasing the all the new viruses. The cell damage is what makes you feel ill.

Immune System:

  • Your skin, hair and mucus in your breathing pipework (respiratory tract) stop a lot of nasty things getting inside your body. 
  • To prevent microorganisms getting into the body through cuts, platelets help blood clot quickly to seal wounds (scabs). 
  • But if something does come in, your immune system kicks in and trawls the body to find microbes and has 3 lines of attack.

1) White blood cells consume the foriegn cells and digest them.

2) Produces antibodies. 

-Every invading cells has antigens on its surface (unique molecules - flags). When your white blood cells come across a foreign antigen, they will start to produce proteins called antibodies to lock onto and kill invading cells. The antibodies produced are specific to that type of antigen, they won't lock onto any others. Antibodies are then produced very quickly to kill any other similar viruses or bacteria. If the same person is infected with the same pathogen, the white blood cells will rapidly produce that same antibody





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