Week 7

• What is a virus classified as?

  Obligate intracellular parasite
• Why do viruses require a host cell?

  To replicate and reproduce
• What type of genetic material do viruses contain?

  DNA or RNA

  
• What is the function of the viral capsid?

  Protects the viral genetic material

  
• What surrounds the capsid in some viruses?

  An envelope

  
• How does the viral envelope assist in infection?

  Helps the virus attach to host cells
• What do surface proteins on the virus do?

  Recognize and bind to host cell receptors
• What are the components all viruses have?

  • Viral genome: DNA or RNA
  • Viral capsid: a protein coat

  
• What are the characteristics of enveloped viruses compared to non-enveloped viruses?

  Enveloped Viruses:

  • Have a lipid envelope
  • Sensitive to environmental factors

  
  

  Non-Enveloped Viruses:

  • Lack a lipid envelope
  • Resistant to harsh conditions
• What is the main role of the capsid?

  To protect the viral genomic material

  
• What environmental factors does the capsid protect against?

  pH changes, heat, drying, UV radiation
• How do capsid proteins interact with host cells?

  They bind to specific receptors on host cells
• What are the three forms of capsids?

  1. Helical
  2. Icosahedral
  3. Scaffolded icosahedral

  
• What is the purpose of capsid assembly?

  To form the capsid shell
• What is the triangulation number in capsid structure?

  Determines subunit number and capsid complexity
• What are capsomers?

  Protein subunits that make up the capsid
• What is self-assembly in capsid formation?

  Capsomers assemble without additional energy
• What is cryo-electron microscopy used for?

  • Imaging frozen samples of capsids
  • Captures high-resolution, 3D structures
• How does the viral envelope aid in infection?

  It binds to specific cellular receptors
• What is the role of the viral envelope in viral exit?

  Allows the virus to leave via budding
• What are the differences between enveloped and non-enveloped viruses?

  Enveloped Viruses:

  • Have a lipid envelope
  • Sensitive to environmental factors

  
  

  Non-Enveloped Viruses:

  • Lack a lipid envelope
  • Resistant to harsh conditions
• What is a capsid?

  Protein coat that protects the viral genome

  
• What are peplomers?

  Proteins embedded in the envelope
• What is a virion?

  A complete virus particle
• Who is responsible for virus classification?

  The International Committee on Taxonomy of Viruses
• What phenotypic characteristics are used to classify viruses?

  Morphology, nucleic acid type, replication strategy
• What does the Baltimore Classification System categorize viruses by?

  Nucleic acid type and replication strategy
• How are viruses named based on the disease they cause?

  Example: Poliovirus for poliomyelitis
• What is the role of viruses in the ecosystem?

  They infect all living things
• How do viruses outnumber bacteria?

  Viruses outnumber bacteria by 10:1
• What percentage of human DNA is viral in origin?

  5-8%
• Where are viruses found in the human body?

  Hair, skin, nails, nervous system, etc.
• What are endogenous retroviruses?

  Viral sequences integrated into the human genome
• What is a susceptible cell?

  Has a functional receptor for a virus
• What is a resistant cell?

  Lacks a receptor for a virus
• What is a permissive cell?

  Has machinery to replicate a virus
• What does it mean for virus particles to be metastable?

  Stable enough to protect, unstable to disassemble
• What are the steps of the viral life cycle?

  1. Attachment
  2. Entry
  3. Uncoating
  4. Replication and gene expression
  5. Assembly
  6. Release
• What is pathogenesis in relation to viruses?

  Process by which a virus causes disease
• What are the two main factors in pathogenesis?

  Viral infection effects and immune response effects