acellular microbes

• What are the main types of acellular microbes?

  Viruses, satellites, viroids, prions
• What is the primary function of a virion's parts?

  To facilitate viral infection and replication
• How do enveloped viruses differ from non-enveloped viruses?

  Enveloped viruses have a lipid membrane
• What role do receptors play in the viral replication cycle?

  They determine host cell attachment
• How do viruses compare to virophages, satellites, viroids, and prions?

  Viruses are larger and more complex
• Why are viruses considered obligate intracellular pathogens?

  They cannot replicate outside host cells
• What is the size range of virions?

  ~10–400 nm in diameter
• What is a nucleocapsid composed of?

  Nucleic acid and a protein coat
• What are the three types of capsid symmetry?

  Helical, icosahedral, complex
• What is the structure of helical capsids?

  Hollow tubes with protein walls
• What defines an icosahedral capsid?

  20 equilateral faces and 12 vertices
• What are capsomers in icosahedral capsids?

  Units made of 5 or 6 protomers
• How do complex symmetry capsids differ from helical and icosahedral capsids?

  They do not fit into those categories
• What is the function of viral envelopes?

  To protect and aid in host cell entry
• Where do animal virus envelopes typically arise from?

  Host cell plasma or nuclear membranes
• What is the role of envelope proteins in viruses?

  Involved in attachment to host cells
• What types of nucleic acid can viral genomes contain?

  DNA or RNA, not both
• What is the Baltimore classification system based on?

  Viral genome structure and replication strategy
• What are the steps in the viral replication cycle?

  Attachment, penetration, transcription, replication, assembly, release
• What determines the host preference of a virus?

  The receptor it binds to on the host
• How do enveloped viruses enter host cells?

  By membrane fusion or endocytosis
• How do non-enveloped viruses typically enter host cells?

  By receptor-mediated endocytosis or direct injection
• Where do dsDNA viruses usually replicate?

  In the host cell nucleus
• What do RNA viruses require for genome replication?

  Virally encoded enzymes
• What is the function of RNA-dependent RNA polymerase (RdRp)?

  To replicate RNA genomes
• What is the difference between positive and negative sense RNA?

  Positive sense can be translated; negative cannot
• What are replication factories in viruses?

  Membrane-protected complexes for replication
• How do non-enveloped viruses typically release from host cells?

  By lysing the host cell
• How do enveloped viruses typically release from host cells?

  By budding from the host cell membrane
• What is the role of actin tails in poxvirus dissemination?

  To propel the virus through host membranes
• What is the Sputnik virophage known for?

  Infecting other viruses like mimivirus
• What do satellites require for replication?

  A helper virus
• What are viroids composed of?

  Closed, circular ssRNAs
• What is the primary effect of prions on the brain?

  Causes loss of neurons
• What is the normal form of prion protein called?

  PrP_C
• What happens to normal prion proteins in the presence of PrP_Sc?

  They change conformation to abnormal form
• What is the recommended study practice after lectures?

  Write notes to aid revision
• Where can students find useful resources for virology?

  At viralzone.expasy.org