Health and disease

• Microorganism


  A microscopic living thing that causes disease
• Pathogen


  A microorganism that causes disease
• Bacterial cell structure


  • Cell surface membrane
  • Cell wall
  • Slime capsule
  • Ribosomes
  • Chromosomal circular DNA (NOT IN NUCLEUS)
  • Plasmids (extra loops of DNA)
  • Flagella
• Virus structure


  • DNA/RNA (genetic information)
  • Protein coat
• Viruses are smaller than bacteria
• Viruses are considered not living as they can only reproduce inside a host cell
• Virus reproduction


  1. Virus attaches to host cell

  2. Virus injects genetic material into cell

  3. Host cell reads virus genetic information and makes new copies of virus

  4. Cell bursts open and viruses are released
• In real life, bacteria are bigger than viruses
• Communicable diseases


  • Flu
  • TB
  • Athletes foot
• Flu is caused by a virus pathogen
• TB is caused by a bacteria pathogen
• Athletes foot is caused by a fungus pathogen
• Primary defence- stops pathogens entering the body

  • Tears
  • Nasal mucus
  • saliva
  • stomach
  • Ear wax
  • Mucus and cilia in air ways
  • skin
• Tears


  • Wash away irritating substances and pathogens
  • Lysozyme is a chemical found in tears that can kill bacteria
  • There are 3 types of tears (basal tears to keep the eyes moist, reflex tears in response to physical triggers, and emotional tears)
• Skin


  • Provides a physical barrier to the entry of pathogens
  • Skin is slightly acidic to reduce the growth of bacteria
  • Skin accounts for about 15% of your body weight
  • The average person has about 300 million skin cells
  • The skin renews itself every 28 days
• Air ways


  1. Mucus in airways traps bacteria

  2. Cilia (small hairs covering the airway cells) then waft the bacteria out of the lungs
• Stomach


  Contains hydrochloric acid that kills bacteria in food
• Nose


  • Mucus in nose helps trap bacteria in the air
  • Your nose produces nearly a litre of mucus a day (most of which you swallow without realising)
• Ear wax


  • Wax traps bacteria and chemicals in ear wax help reduce growth of bacteria
  • Ear wax is self cleaning
  • Using a cotton bud to clean out ears can actually be damaging
• Saliva


  • Contains chemicals that help reduce the growth of bacteria that may cause disease
  • Every year you could produce up to 2 bath tubs of saliva
• White blood cell engulfing and digesting bacteria
• Antigen


  Proteins on the surface of the bacteria
• Antibodies


  • Produced by the white blood cell to bind to proteins on the bacteria
  • Can make bacteria burst open
  • Can 'label' bacteria to be engulfed by white blood cell
  • Can make pathogens stick together making them easier to engulf
• Antibodies have to be complementary to the proteins on the surface of the bacteria for them to be able to destroy the bacteria
• If a person was very ill, injecting them with antibodies could help
• Babies' white blood cells are not as good at fighting pathogens, so they may get extra antibodies from somewhere else
• Immunity


  When an organism does not become ill even though they are infected with a pathogen
• Primary immune response


  1. Triggered when a person is first infected with a pathogen

  2. Produces some antibodies
• Secondary immune response


  1. Triggered when a person is infected with a pathogen they have encountered before

  2. Produces many antibodies very quickly to destroy the pathogen before it makes the person ill
• Vaccine


  A dead or weakened version of a pathogen that is injected into a person to trigger the primary immune response and create memory cells
• Vaccination


  Leads to immunity
• White blood cells produce antibodies that can bind to proteins on the surface of bacteria
• Antibodies can make bacteria burst open, label bacteria to be engulfed by white blood cells, and make pathogens stick together making them easier to engulf
• Antibodies have to be a particular shape to bind to the proteins on the surface of a specific pathogen
• Babies get extra antibodies from their mothers to help fight pathogens
• Chicken pox is caused by the chicken pox virus
• Antibiotics can only be used to kill bacteria, not viruses
• Memory cells are created during vaccination, allowing the secondary immune response to be triggered if the person is later infected with the real pathogen
• The primary defence stops pathogens entering the body, while the secondary defence is the immune response