B3

• Pathogens

  • Bacteria
  • Viruses
  • Fungi
  • Protists
• Viruses

  Reproduce by injecting genes into cells which makes them produce more copies
• Viruses


  • Measles (causes a rash spread by droplets)
  • HIV (an STD that gives you aids and compromises the immune system)
• Bacteria


  Release toxins into your body that damages your cells
• Bacteria


  • Salmonella (food poisoning)
  • Gonorrhoea (an STD which causes a yellow discharge)
• Fungi


  Damages cells
• Protists

  Single celled organism
• Protists


  • Malaria (infects red blood cells)
• Plant diseases

  • Rose black spot (causes leaves to fall off)
  • Tobacco mosaic virus (causes discoloured leaves, less chlorophyll and stunted growth)
• Skin, mucus, acids, enzymes

  • Kill pathogens
• Lymphocytes


  White blood cells that produce antitoxins to neutralise toxins made by pathogens, stop viruses from damaging cells and cause them to clump together
• T cells


  Store the correct antibody in lymph nodes ready for next time (immunity)
• Phagocytes


  White blood cells that ingest pathogens
• Vaccine

  Introduces a dead version of a virus into your body, so you can gain immunity without becoming ill
• Antibiotics

  Kill bacteria but not viruses
• Many drugs are derived from nature such as aspirin (a pain killer) that came from trees and penicillin (the first antibiotic) that came from a mould
• Synthetic drugs


  Cost a lot of money to develop, are put through trials to assess for efficacy, toxicity and dose, tested on cell tissue, then animals then humans
• Blind trial


  Test group given the drug, control group given a placebo, without any of them being made aware
• Double blind trial


  Doctor doesn't know which drug is which to eliminate bias