biology 🧬

• Pathogen


  An organism that causes disease
• Pathogens


  • Bacteria
  • Viruses
• Host


  Organisms which harbour pathogens
• Transmissible diseases


  Diseases that can be spread from host to host through contact with an infected organism, or through other mediums such as food, water, waste and bodily fluids
• Preventing the spread of disease

  1. Preparing food hygienically

  2. Treating waste and sewage

  3. Maintaining good personal hygiene
• Body's first line of defense against infection

  • Mechanical barriers (hairs in the nose and skin)
  • Chemical barriers (mucus, stomach acid and tears)
• Immune response


  Occurs to kill pathogens that have infected the body, involving phagocytosis and antibody production by white blood cells
• Antigen


  Specific protein on the cell membrane of a pathogen
• Antibody


  Produced by lymphocytes, binds to the antigen to produce an antibody-antigen complex
• Antibody binds to antigen

  Pathogens clump together and are made harmless, then killed directly or marked for destruction by phagocytes
• Autoimmune disease


  Disease caused by an immune response on healthy body cells, which are targeted and destroyed by the immune system
• Autoimmune disease


  • Type 1 diabetes
• Active immunity


  Can be gained after an infection, or through vaccination
• Gaining active immunity through infection

  1. Pathogen is killed

  2. Memory cells remain

  3. If same pathogen enters body again, memory cells recognize antigens and produce new antibodies more quickly, giving long-term immunity
• Gaining active immunity through vaccination

  1. Dead or attenuated version of pathogen given to patient

  2. Antigens evoke immune response, producing antibodies

  3. Memory cells produced, giving long-term immunity
• Herd immunity


  Large amount of population is vaccinated and thus immune to the pathogen, so the disease cannot spread as there are only a few people left who can still become infected
• Passive immunity


  Short-term defense against a pathogen, gained through acquiring antibodies from another individual
• Passive immunity


  • Antibodies passed to baby through mother's milk
  • Injections of antibodies from a donor
• Passive immunity does not involve the production of memory cells