10.2.1 Classification: bacteria, fungi and viruses

• 5 kingdoms of living organisms

  • Prokaryotes
  • Fungi
  • Protists
  • Animals
  • Plants
• Prokaryotes


  • No nucleus (DNA is free in the cytoplasm)
  • No membrane-bound organelles
  • Have a cell wall made of PEPTIDOGLYCAN
  • Have small, extra circular DNA called PLASMIDS
  • Sometimes they have FLAGELLUM
  • Some also have a slime capsule
• Bacteria come in different shapes and are normally about 1-10 micrometers in size
• Fungi


  • Most are multicellular organisms
  • Not capable of photosynthesis: they are heterotrophic because they use complex organic compounds as sources of energy and carbon
• Hyphae


  Long thread-like structures that are branched and spread over the food, secreting enzymes that digest the food which the fungi then take up (saprotrophic nutrition)
• Some fungi, like YEAST, are unicellular
• Yeast


  • Have a nucleus containing DNA
  • Have membrane bound organelles like mitochondria
  • Have a cell wall made of CHITIN
  • Have ribosomes to make proteins
• Viruses


  • Not classed as living organisms (they do not show the 7 characteristics)
  • All viruses are parasites and cause harm to their host (ie cause disease)
  • They are very small (much smaller than bacteria)- 0.1 micrometres

  
• Structure of Viruses


  • They have a protein coat (capsid)
  • Their genetic material can be either DNA or RNA
  • They have spikes that can recognize cells to infect them

  
• Viruses come in different shapes