Common Features: Prokaryotic Organisms (Edexcel IGCSE Science)

Prokaryotes

Spec point — 1.3 · "describe the common features shown by prokaryotic organisms such as bacteria Bacteria: these are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms. Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia."

Prokaryotes

• All living organisms can be grouped together into groups based on the characteristics and features that they share:

  • Plants
  • Animals
  • Fungi
  • Protoctists
  • Prokaryotes

• The prokaryotes are different from the other four groups, which are all eukaryotes

• Features of prokaryotic organisms include:

  • they are single-celled
  • they have no nucleus
  • the nuclear material is found in the cytoplasm

• Bacteria are prokaryotic organisms

Bacteria

• Bacteria share the following biological characteristics:

  • they are microscopic,single-celled organisms
  • they have a cell wall, cell membrane, cytoplasm and plasmids
  • they lack a nucleus but contain a circular chromosome of DNA
  • they lack mitochondria and have no other membrane-bound organelles

• Examples of bacteria include:

  • Lactobacillus bulgaricus

    • A rod-shaped bacterium used in the production of yoghurt from milk

  • Pneumococcus

    • A spherical bacterium that acts as the pathogen causing pneumonia

• Bacteria feed in different ways:

  • Some bacteria carry out photosynthesis despite having no chloroplasts; this is because they still possess chlorophyll-like substances and have the enzymes necessary to synthesise sugars

  • Most feed on other living or dead organisms

    • If they feed on dead organic matter then they are known as saprobionts or decomposers

Bacteria have a cell wall, cell membrane, cytoplasm, plasmids and circular DNA

Components of prokaryotic and eukaryotic cells table