cell parts

• Archaea and Eukarya are more closely related genetically than Archaea and Bacteria
• Extremophiles


  • Can be found in environments with extreme temperatures like thermal vents, ice sheets and deserts
• Extremophiles can be as large as 5μm in diameter
• The largest known prokaryote is the margarita, which can be up to 750μm long
• Cell arrangements of prokaryotes

  • Cocci (occur singly or in bunches)
  • Bacilli (usually solitary but can also join up)
  • Spirilla (usually solitary)
• Prokaryotic cell wall


  • Made of peptidoglycan - a complex of sugars and proteins
  • Provides protection from desiccation and the immune system
• Gram-positive cells have a thick layer of peptidoglycan, while Gram-negative cells have a thin layer and an outer membrane of lipopolysaccharides
• Archaea have cell walls made of polysaccharides, not peptidoglycan
• Cell wall


  Prevents the cell from bursting in a hypertonic environment
• Gram staining identifies Gram-positive (thick peptidoglycan layer) and Gram-negative (thin peptidoglycan layer and outer membrane) bacteria
• Penicillin inhibits peptidoglycan cross-linking in the cell wall
• Archaeal cell membranes


  • Adapted to extreme temperatures by changing the lipid composition
  • Contain lipid monolayers instead of the typical phospholipid bilayer
• Archaea lack membrane-bound organelles and have a nucleoid instead of a true nucleus
• Archaea have specialized membrane infoldings that carry out metabolic processes
• Carbon sources for prokaryotes

  • Chemoautotrophs (use inorganic carbon compounds)
  • Chemoheterotrophs (use organic carbon compounds)
• Prokaryotes have a single circular chromosome and may also have plasmids
• Prokaryotes can have appendages like fimbriae to attach to surfaces
• Prokaryotes can reproduce by binary fission and form endospores under hostile conditions
• Prokaryotes can acquire foreign DNA through transformation, conjugation, and transduction
• Energy sources for prokaryotes

  • Phototrophs (use sunlight)
  • Chemotrophs (use chemical energy)
• Cyanobacteria are photosynthetic prokaryotes that produce atmospheric oxygen
• Nitrogen-fixing prokaryotes are important in plant ecosystems
• Gut microbiota play a role in human health and development
• Humans have over 600 bacterial species, with only 16.4% of taxa identified
• Zoonotic diseases can be transmitted between humans and animals
• Antibiotic resistance emerged in the 1950s, often due to R-plasmids that confer resistance
• Bacteriophages are viruses that infect bacteria
• Bacteriophage structure


  • Size range from 20-1500nm
  • Can have DNA or RNA genomes, single or double-stranded
  • Can be filamentous, icosahedral, or have a head and tail structure
• Bacteriophages use cell surface receptors to bind and infect host cells
• Bacteriophages can have lytic or lysogenic life cycles
• Genetic variation in viruses can occur through mutation, recombination, and reassortment
• Bacteriophages are the most complex viruses, with the most complex capsids
• Viruses can produce toxins that lyse the host cell
• CRISPR-Cas systems in bacteria provide adaptive immunity against viruses
• Many viruses, such as adenoviruses and papillomaviruses, can cause human diseases