B3: Infection and responses

• Communicable diseases


  Caused by pathogens that can be viruses, bacteria, fungi or protists
• Pathogens


  • They reproduce in your body and cause damage
• Virus


  A protein casing that surrounds genetic code that it injects into a cell, causing the cell to produce more copies of the virus. The cell then explodes and the virus goes on to infect more cells.
• Viruses


  • Measles
  • HIV
• Measles


  A virus that causes a rash and can be deadly. Spread by droplets from sneezes or coughs.
• HIV


  An STD/STI that compromises the immune system, also called AIDS. Can be spread by sharing needles.
• Bacteria


  Release toxins that damage body cells, e.g. salmonella in undercooked food or gonorrhea that causes a yellow discharge.
• Fungi


  Do something similar to bacteria, e.g. athlete's foot.
• Protists


  Single-celled parasites that do all sorts of different things, e.g. malaria is caused by a protist that burrows into red blood cells.
• Vector


  An organism that transmits a disease, e.g. mosquitoes for malaria.
• Plant infections


  • Rose black spot
  • Tobacco mosaic virus
• Body's defences


  • Skin as first barrier
  • Nose, trachea, digestive system can trap or destroy pathogens
  • White blood cells, including lymphocytes that produce antitoxins and antibodies
  • Antibodies neutralize pathogens and mark them for destruction by phagocytes
• Antigen


  Specific shape on a pathogen that an antibody must fit to neutralize it
• Immunity


  Immune system stores copies of antibodies and antigens to be ready to stop infection next time
• Vaccine


  Dead or inert version of a pathogen that exposes the immune system to produce antibodies without causing infection
• mRNA vaccine


  Injects DNA/mRNA to trick cells into synthesizing part of a virus, including the antigen
• Antibiotics


  Kill bacteria, don't kill viruses. Penicillin was the first one. Bacteria can become resistant over time.
• Drug development


  Drugs used to be extracted from plants/organisms, now mostly synthesized. Undergo lab, animal, and human trials, including blind and double-blind studies, to test effectiveness and side effects.
• Monoclonal antibodies


  Made from clones of a cell that produces a specific antibody. Used for treatment, diagnosis, and identification of molecules.