Structure of prokaryotic cells and of viruses

• Describe the general structure of prokaryotic cells

  Always present:

  • Cell-surface membrane
  • Cell wall - contains murein/peptidoglycan (Glycoprotein)
  • Cytoplasm
  • 70s ribosomes
  • Circular DNA - free in cytoplasm and not associated with proteins

  Sometimes present:

  • Slime capsule
  • Plasmids - Small rings of DNA
  • Flagella
• Explain why viruses are described as acellular and non-living

  • Acellular - not made of cells, no cell membrane/cytoplasm/organelles
  • Non-living - have no metabolism, can't independently move/respire/replicate/excrete
• Describe the general structure of a virus particle

  1)Nucleic acids surrounded by a capsid (protein coat)

  2)Attachment proteins allow attachment to specific host cells

  3)No cytoplasm, ribosome, cell wall, cell-surface membrane etc.

  4)Some also surrounded by a lipid envelope e.g. HIV