Structure of Prokaryotic cells

• Prokaryotic cells are a cell with no membrane bound organelles
• Viruses are not a prokaryotic cell as they are unable to reproduce without a host cell. They also don't have any membrane bound organelles within them.
• Some bacterial cells contain a layer of mucilaginous slime called a capsule. This aids in protection
• A bacterial cell does not contain a double helix of DNA it instead has circular DNA.
• The cell wall is a physical barrier that protects against the entry of certain substances, mechanical damage and osmotic lysis. This is made of murein in a bacterial cell.
• Circular DNA contains the genetic information for cell replication
• A plasmid is a circular piece of DNA which can reproduce itself independently and can be transferred between bacteria. This may confer resistance to antibiotics
• The flagellum is used for locomotion. Some species contain many and others contain none.
• Features found in prokaryotic cells and not in eukaryotic cells:

  • DNA free cytoplasm
  • Murien in cell wall
  • No membrane bound organelles
  • Circular DNA with protiens
• Every virus has a capsid. These control entry and exit out of the virus and helps keep DNA safe.
• Both the matrix and lipid envelope are optional for viruses, these provide an extra layer of protection and is used to get inside the host cell
• Attachment proteins are in all viruses. These attach to other cell receptors to enter the cell. These attach to the capsid if no envelope or matrix is present.
• 3 features found in all viruses:

  • Capsid
  • Attachment proteins
  • Genetic material
• Viruses are acellular as they are not made up of a cell, have no membrane or cytoplasm
• Antibiotics target cell walls which viruses lack, hence why they don't work on viruses
• Virus replication:

  • Attach to the cell receptors and enters the cell. The envelope is lost at this point.
  • Uncoating (removes capsid) which releases the genetic material. Reverse transcription may happen at this stage
  • Intergrates into host DNA
  • Viral proteins are transcribed and translated
  • New viruses are assembled from the proteins
  • New viruses either bud off (lysogenic) or burst / lyse the cell (litic)
• A bacterial cell is an example of a prokaryotic cell. A prokaryotic cell contains no membrane bound organelles.
• The cell wall is a physical barrier which protects against the entry and exit of certain substance, mechanical damage and osmotic lysis. This is made of murein in a bacterial cell, and cellulose in a plant cell.
• A capsule is the mucilaginous slime which is secreted by some bacteria. It aids in protection
• Plasmids are circular pieces of DNA. They can reproduce independently and can be transferred between bacteria. They may confer resistance to antibiotics
• Cytoplasm is a jelly like substance that contains enzymes and other soluble material.
• Ribosomes synthesise polypeptides. Bacteria contain the 70S type.
• Flagellum is used for locomotion. Some species contain many whilst some contain none.
• Viruses are not prokaryotic cells as they are unable to reproduce without a host cell. They also contain no organelles within them.
• A capsid is contained in every virus. They control the entry and exit of the virus and keep DNA safe.
• The matrix is optional for viruses. They also offer an extra layer of protection and help to enter the host cell.
• The lipid envelope is optional for viruses. They also offer an extra layer of protection and enter the host cell.
• Attachment proteins attach to the other cell receptors. These are found in all viruses and can attach to the capsid if no envelope is present.
• Reverse transcriptase converts RNA back into DNA. These are contained in all RNA viruses.
• Virus replication:

  • Attach to cell receptors and enter the cell. The envelope is then lost at this stage
  • Uncoating releases genetic material. Reverse transcription can also happen.
  • Intergrates into host DNA
  • Viral proteins are transcribed and translated by the host cell
  • New viruses are assembled from these proteins
  • The virus will either bud off (lysogenic) or burst the cell (lyslitic)
• Describe how HIV replicates

  Attachment proteins attach to cell receptors to enter the cell

  RNA will enter the cell, once attached

  Reverse transcriptase converts the RNA into DNA

  Viral proteins are produced and assemble a new HIV virus particle