B3 revision

• Pathogen

  A harmful microorganism that causes disease
• Types of pathogens

  • Bacteria
  • Fungi
  • Virus
  • Protist
• Ways pathogens spread

  • Air
  • Water
  • Food
  • Sexual activities
  • Vectors
• Ways to stop the spread of pathogens

  • Wash hands
  • Vaccination
  • Kill vectors
  • Disinfection
  • Cook food well
• Ways the body defends itself from pathogens

  • White blood cells
  • Skin as a barrier
  • Stomach acids
• Viral diseases

  Viruses spread within the body by reproducing and cloning themselves within cells
• Symptoms of measles: red spots, itchy
• Symptoms of HIV: vomiting, diarrhoea, weak
• Symptoms of TMV: yellow colour on leaf
• How measles spreads

  Direct contact, coughs
• How HIV spreads

  Sharing needles
• How TMV spreads

  Healthy leaves touching infected leaves
• Prevent spread of measles: hygiene
• Prevent spread of HIV: safe sex
• Types of body defences

  • Skin as a barrier
  • Stomach acids
  • Mucus
  • Nose hairs
  • Tears (antiseptic)
• Types of plant defences

  • Physical defences (e.g. thorns)
  • Chemical defences (e.g. poisonous toxins)
  • mechanical defences ( leaves droop or curl when touched)
• Lymphocytes

  A type of white blood cell that produce antitoxins to neutralise toxins
• Antibodies

  Bind to antigens to stop viruses from infecting cells
• Phagocytes

  A type of white blood cell that ingests pathogens bound to antibodies and antigens
• T cells

  Can store copies of antibodies in lymph nodes, providing immunity
• Vaccine

  Small quantities of dead or weakened pathogens put into the body to gain immunity
• Herd immunity

  Infection reduced due to a large amount of the population being immune
• People who cannot be vaccinated

  • The old
  • The very young (due to weak immune system)
• Antibiotics kill bacteria, not viruses
• If you do not finish your full course of antibiotics, bacteria will remain and multiply, making you antibiotic resistant
• Alexander Fleming

  Discovered penicillin from a mould
• Where did Aspirin come from?

  willow tree
• Antiviral drugs

  Target specific viruses in the body but can damage cells
• Digitalis

  A drug made from the foxglove plant
• Synthetic drug development

  1. Trials to assess efficacy, toxicity, and dose

  2. Testing on cell tissue, animals, then humans
• Blind trial

  Test group given drug, control group given placebo without being aware
• Double blind trial

  Doctors and the person don't know which drug is which, to eliminate bias
• Monoclonal antibodies

  Antibodies produced by clones of a cell that produces a desired antibody
• Process of producing monoclonal antibodies

  1. Lymphocytes harvested from mouse

  2. Tumour cells grown in tissue culture harvested

  3. Lymphocytes can make antibodies but can't divide, tumour cells can divide but can't make antibodies

  4. Lymphocytes and tumour cells combined to make hybridoma cells

  5. Hybridoma cells can make specific antibodies and divide rapidly

  6. Hybridoma cells then cloned to produce monoclonal antibodies which are separated, purified then used
• Uses of monoclonal antibodies

  • Diagnosis of disease (e.g. prostate cancer)
  • Research (observe binding process)
  • Cancer treatment (trigger immune system to attack cancer cells)
  • Pregnancy test (HCG binds to monoclonal antibodies)
• Advantages of monoclonal antibodies

  • Does not affect healthy cells, used to treat a range of conditions
• Disadvantages of monoclonal antibodies

  • Causes side effects like immune reactions in humans due to being a mouse antibody, quite expensive development, producing right antibodies is difficult
• What is phagocytosis?

  white blood cells engulf and destroy labelled pathogens