On the fringe of classification

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On the fringe of classification

• I am not a cell
• I have no nucleus
• I can reproduce if the conditions are right
• I have no metabolism
• What am I?

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Viruses

• Bio 11

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Living and not living

• Living because
• Can reproduce
• Resemble first forms of life on earth
• Have evolved
• Have nucleic acid (DNA, RNA)
• Movement
• Can mutate and change

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Living and not living

• Not-living because
• Not cellular
• No organelles
• No metabolism
• No cell membrane or
• cell wall

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Anatomy

• Made of genetic material (blue print) surrounded
  by a protein coat
• Shapes of viruses vary greatly (spherical,
  rod-like, cubical, many sided)
• Example of a virus structure ?

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Reproduction

• Do not grow
• Must invade a living cell!
• Can reproduce but only with the help of a host
  cell (living cell)
• Viruses are specific and only invade certain
  types of cells

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Stages of reproduction/life cycle

1. Absorption virus attaches to host cell
2. Entry virus injects genetic material into the
   cell
3. Replication host cell will produce new virus
   parts instead of doing its normal work
4. Assembly new viruses are put together and
   completed
5. Release host cell breaks open, new viruses then
   attach to other cells in the area and the process
   starts again

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Lytic verse Lysogenic

1. Lytic a virus life cycle during which a virus
   takes over a host cell, makes copies of itself
   and then destroys the host cell
2. Lysogenic the virus does NOT destroy the host
   cell. The virus permanently inserts its DNA into
   the host cell DNA and stays there

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Bacteriophage

• Is a type of virus that commonly infects bacteria
  cells.

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Characteristics used to classify viruses

• 1. Type of nucleic acid viruses have either
  single-strand RNA or double-strand DNA, but never
  both.
• 2. Physical shape Viruses are found in several
  general shapes
• 3. Envelope whether or not they have an outer
  membrane (Gram or Gram -)
• 4. Type of host cell most viruses are very
  specific about the type of cell they invade.
  There are specific sites called receptor sites
  that the viruses attach to on the host cell's
  surface

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Things that viruses cause

• Common cold
• Flu
• German measles
• Mumps
• Chicken Pox
• Small Pox
• Cold Sores
• Herpes
• Chicken pox
• Hepatitis
• Aids
• West Nile

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How to treat Viral infections

• NOT WITH Antibiotics specifically attack the
  metabolism of a bacterial cell. Since viruses use
  only the reproductive machinery of a cell,
  antibiotics are of no use in destroying viruses.
• Antiviral drugs interfere with the synthesis of
  viral nucleic acid or with the formation of viral
  capsids during replication.
• White blood cells engulf viruses in the blood
  and "digest" them.
• Interferon is a 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.