What is a Virus?

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What is a Virus?

• Particle of nucleic acid and protein which
  reproduce only by infecting living cells

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Do viruses qualify as living things?

• Much smaller and less complex than cells
• Consist of either DNA or RNA enclosed in a
  protein coat called a capsid
• Do not grow
• Have no nucleus, cytoplasm, or membranes
• Do not carry out cellular functions or generate
  metabolic energy

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Do viruses qualify as living things?

• NOThey are obligate intracellular parasites,
  meaning that they require a host cell to
  reproduce.

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LyticCycle
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Lytic Cycle (Viral Reproduction)

• DOCKING with the host receptor protein
• PENETRATION of the viral nucleic acid into the
  host cytoplasm
• BIOSYNTHESIS of the viral components
• Assembly (MATURATION) of the viral components
  into complete viral units
• RELEASE of the completed virus from the host
  cell

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Lysogenic Cycle
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Lysogenic Cycle
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Lysogenic Cycle
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Retroviruses

• Use RNA instead
  of DNA

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Prions

• Protein infectious particles
• Contain no RNA or DNA

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Interferon

• Protein produced by cells when exposed to a
  virus.
• This protein binds to the cell membranes of
  neighboring cells and "interferes" with the
  ability of a virus to enter the cell.

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Small Pox
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Polio
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Herpes Simplex
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Hepatitis
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Varicella Zoster
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Mumps
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Measles - Rubeola
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Other Viruses

• Influenza Virus
• Rubella
• Parvo-virus
• Epstein Barr Virus
• Hanta Virus
• (HPV) Human Papilloma Virus
• (RSV) Respiratory Syncytial Virus
• Rabies
• Rhinovirus
• Rotavirus
• West Nile Virus