Viruses

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Viruses
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What is a Virus?

• They are NON-LIVING particles.
• ½ to 1/100 the size of a living bacteria.
• They are NOT cells.
• They have NO characteristics of life.
• All they CAN do is make copies of themselves, but
  must have the help of living cells to do so!

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How do we name Viruses?

• Because they are non-living we cannot
  scientifically name them as other living things!
• They are named for the diseases they cause!
• Rabies
• Polio
• Influenza

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Virus Anatomy
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Viral Structure

• Inner core of Nucleic AcidDNA or RNA (Viral DNA
  or RNA)
• Protein Capsid
• Some have an envelope made of cytoplasm material.

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Virus Vocab

• Host Cell cell virus replicates in
• CAPSID protein shell that encloses
  
• nucleic acid (DNA or RNA)
• Nucleocapsid nucleic acid capsid
• Lysis bursting of a cell
• Lytic Cycle Virus replication that kills the
  cell.
• Lysogenic Cycle Virus replication that does not
  
• kill the cell.

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Virus Invading a Cell
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How Do We Classify Viruses?

• Kind of nucleic acid (DNA or RNA)
• Shape of the Capsid
• Size
• Infect plant, animal, or bacterial cells.

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Virus Replication
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Polio VirusSource Childrens Hospital
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Influenza VirusFlu
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AIDS Virus Anatomy
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AIDS Virus
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Viral Replication

• A virus can replicate only after entering a
  living cell and taking over the metabolism.
• The virus injects the viral nucleic acid into the
  host cell like a syringe.
• The virus makes copy of cell to release from the
  host cell.
• This is called the Lytic Cycle.

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The Lytic Cycle
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Lytic Cycle

• STEP 1
• Attachment and Entry
• A virus injects its nucleic acid into a host
  cells cytoplasm.
• Not all viruses kill the cells they infect.

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Lytic Cycle

• STEP 2
• Provirus Formation
• The viral nucleic acid is called provirus when
  it becomes part of the hosts chromosomes.