Biology 4.6

• Micro-organisms


  Living things that are too small to see with the eye and are everywhere
• Micro-organisms can be helpful or harmful
• Micro-organisms live in our gut and help with our digestion or recycle nutrients by decaying dead organisms
• Some micro-organisms can cause harm and they are called pathogens
• Types of pathogens


  • Virus
  • Bacteria
  • Protist
  • Fungi
• Bacteria


  • They are about the size of an average cell
  • They can grow outside of the cell and don't need a host to reproduce
  • They don't have a nucleus, chloroplast or mitochondria
  • They exist as single cells and move about using flagella
  • They can cause damage directly or by producing toxins
• Viruses


  • They are the smallest pathogens and can be seen with a light microscope
  • They aren't considered alive because they don't complete all of the seven life processes
  • They can only reproduce in a host
  • They evolve and change to become more infectious
• Protists


  • They are larger than bacteria, have a nucleus and belong to the eukaryotic kingdom
  • They consist of one cell
• Fungi


  • They are the largest out of all the pathogens
  • Not all fungi are micro-organisms like mushrooms
• Examples of bacteria


  • Salmonella
  • Cholera
  • Food poisoning
  • Tuberculosis
• Examples of viruses


  • Flu
  • Cold
  • HIV
  • Measles
  • Possibly AIDS
• Protist


  • Malaria
• Fungi


  • Athlete's foot
• Ways pathogens can spread


  • Direct contact (sexual, shaking hands, coughing)
  • Water (dirty water can transmit diseases like cholera)
  • Air (sneezing can spread virus particles)
  • Food (undercooked or reheated food can cause bacterial diseases like E. coli)
• Vector


  Any organism that can spread a disease
• Vectors


  • Mosquitoes
  • Ticks
  • Rats
• Vaccines


  Allow a dead or altered form of a pathogen to enter the body, which causes the white blood cells to produce complementary antibodies that target the pathogens and make memory cells
• How vaccines work


  1. Pathogen enters body

  2. White blood cells produce antibodies

  3. Antibodies target pathogens

  4. Memory cells are made
• Common vaccines for babies and children


  • MMR
  • Tetanus
  • Whooping Cough
• Purpose of vaccines


  • Provide long-term or possibly lifelong immunity
  • Prevent pathogens from finding a host and spreading
  • Increase immunity to the point where the disease dies out
• Reasons against vaccinations


  • Some side effects and risks can cause serious complications
  • Some may believe the vaccine is worse than the disease
  • Less vaccinated means the pathogen can find a host and easily spread
• Primary and secondary immune response


  1. Primary response: First exposure to pathogen

  2. Secondary response: Second dose of same pathogen causes white blood cells to quickly produce lots of relevant antibodies to prevent infection
• Antibiotics


  Substances that slow down or stop the growth of bacteria. They can be taken to cure the disease by killing the pathogen, but are only effective against bacterial diseases, not viral ones.
• Penicillin


  An antibiotic which was discovered by Sir Alexander Fleming in 1928. He noticed that some bacteria he left in a petri dish had been killed by the naturally occurring penicillium mould.
• These problems lead to the forming of bacteria that is antibiotic resistant
• Superbugs


  Bacteria that resist most of the antibiotics used today
• To prevent the spreading of MRSA


  1. Wash hands before each procedure

  2. Use alcohol gels/sanitiser

  3. Screen patients for MRSA

  4. Ensure the hospital is cleaned thoroughly often
• To slow down the evolution of antibiotic resistant bacteria


  1. Doctors avoid prescribing antibiotics whenever possible

  2. Doctors vary the antibiotics they prescribe