Virology Quiz: Understanding Viruses

Viruses

• Virology is the branch of microbiology that studies viruses
• Viruses cannot replicate independently; they need a host cell
• Viruses cannot produce energy on their own
• Viruses can be seen by a light microscope (LM)
• Viruses can be seen by an electron microscope (EM)
• Viruses have either DNA or RNA, but not both
• Viruses have few or no enzymes
• Viruses have many proteins
• Viruses have no mitochondria
• Viruses are prokaryotes or eukaryotes (viruses are not cells)

Viral Structure

• The viral structure consists of a capsid (protein coat) and nucleic acid (DNA or RNA)
• The capsid is made of protein subunits called capsomeres
• Viruses may be enveloped or non-enveloped
• Envelopes are made of lipids
• Viruses are categorized by shape (helical, polyhedral, complex)

Viral Classification

• Animal viruses
• Plant viruses
• Bacterial viruses (bacteriophages)
• Viruses that affect fungi (mycophages)
• Viruses that affect blue-green algae (cyanophages)

Virus Replication

• Adsorption: virus attaches to host cell receptors
• Penetration: virus enters host cell
• Replication: viral components replicated inside host cell
• Assembly: viral components assembled to form new viruses
• Release: newly formed viruses released from host cell (lytic or lysogenic pathway)

Viral Replication (details)

• Plant viruses:
  • Transfer of infection from infected cells to non-infected cells
  • Direct mechanical inoculation
• Animal viruses:
  • Fusion of the viral envelope with the host cell membrane
  • Engulfment (endocytosis)
• Bacteriophages:
  • Lytic: viral DNA takes over host cell and the cell ruptures
  • Lysogenic: viral DNA integrates into the host DNA (prophage)
    • Prophage is replicated along with host DNA
    • Prophage can become active and enter the lytic phase

Virus Cultivation

• Methods used:
  • Inoculation of animals
  • Inoculation into embryonated eggs
  • Tissue culture
• Plant viruses:
  • Direct inoculation by rubbing viral suspensions on leaves or using abrasive material
  • Transfer of infection from infected cell to non-infected cells by plasmodesmata
• Bacteriophages:
  • Lytic or lysogenic cycles
  • Attack bacterial cells by binding to specific proteins or carbohydrates in the cell wall

Test your knowledge of virology with this comprehensive quiz! Explore topics related to viral structure, classification, and the unique characteristics that define viruses. Perfect for students and enthusiasts interested in microbiology.