Prokaryotic Cells and Viruses

• What is the difference between prokaryotic and eukaryotic cells?

  Prokaryotic cells are smaller and have no nucleus or membrane bound organelles.
• How is the structure of DNA different from prokaryotes to eukaryotes?

  Prokaryotes have a single, circular DNA molecule that is free in the cytoplasm and not associated with proteins.
• What is the role of circular DNA in bacteria?

  It contains the genetic information for replication of bacteria.
• Prokaryotic cells can store DNA outside of the single circular chromosome using another structure. What is this structure?

  Prokaryotes have rings of DNA called plasmids. Eukaryotes do not have plasmids.
• What are the role of plasmids in bacteria?


  Possess genes that may aid survival e.g. enzymes to break down antibiotics.
• What size of ribosome is found in prokaryotic cells?

  70S
• What molecule makes up prokaryotic cell walls?

  Murein
• What type of molecule is murein?

  Glycoprotein
• What are the main structures of bacterial cells?

  Cell wall; capsule; cell-surface membrane; circular DNA; plasmids.
• What is the role of the cell wall in bacteria?

  Physical barrier to some substances, protects against mechanical damage and osmotic lysis.
• What is the role of the capsule in bacteria?

  Made of mucilaginous slime, it protects against other cells and allows bacteria to stick together for protection.
• What is the role of the cell-surface membrane in bacteria?


  Differentially permeable, controls entry and exit of chemicals.
• How are viruses described?

  A-cellular, non-living particles.
• What range of sizes are viruses?

  Generally between 20-300nm.
• What is the basic structure of a virus?


  Nucleic acids (DNA or RNA) contained within a protein coat called a capsid. Capsid contains attachment proteins. Sometimes with an extra lipid coat.
• Where do viruses reproduce?


  Within host cells.
• What do attachment proteins allow the virus to do?

  Allows the virus to identify itself and attach to a host cell.