Viruses

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Viruses

• Alive or not?

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There are many viruses that affect humans. Here
are a few of them.
The AIDS Virus
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Herpes simplex virus
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Smallpox virus
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Different types of Influenza viruses
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Measles virus
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Ebola Virus
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Viruses attack specific species and often
specific cells.A virus that would affect a human
would not affect different organism.
Bacteriaphage viruses attack only bacteria
Tobacco Mosiac virus Attacks tobacco plants
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Viruses remained undiscovered for so long because
they are very small.
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• The very first virus discovered on the 12th
  February 1892 by Dmitri Iwanowsk (1864-1920), a
  Russian botanist. While studying mosiac tobacco
  disease, he found that the agent causing the
  disease
• was small enough for pass
• though ceramic filter that are
• small enough to trap all bacteria.
• This is generally accepted as
• the beginning of Virology.

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So what is a virus?
The virus is made up of 2 basic structures 1.
A core of DNA or RNA 2. A protein coat
surrounding the DNA or RNA
called a capsid Sometimes they have tail
fibers that help them attach to a host cell.
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Viral reproduction is quite fascinating!

• 1. The virus
• attaches to the
• membrane of a
• host cell.

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2. The virus injects its genetic material into
the host cell.
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• The viral DNA is replicated by the host
• cell.

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4. The viral DNA and protein coats are
produced by the host cell.
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5. The parts of the virus assemble
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6. Viral enzymes break down the membrane
causing the host cell to split open. Now the new
viruses infect neighboring cells.
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So how can you fight a viral infection?

• There are no medications or drugs that can help
  you get rid of a virus.
• Antibodies are produced in the blood (yellow)
  which are specific to the attacking virus (green)

The antibodies disable the virus but only after
you have felt the affects of the illness
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Prevention of Viruses

• Viral infections can be prevented with a vaccine.
• A vaccine is a liquid that contains a weakened
  form of the virus (usually the protein coat)
• This fools the body into producing antibodies so
  that when the real virus attacks, the body is
  ready to disable it.

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Types of Vaccinations you have received.

• Tetanus
• Influenza
• Polio
• Mumps
• Measles
• Rubella
• Chicken pox
• Hepatitis

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How to avoid getting and spreading the flu virus
Wash your hands often
Get plenty Of rest
Drink lots of water
Get a flu shot
Avoid sick people
Dont eat at buffets ?
Eat healthy foods Like fruits and vegetables
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How do viruses and cells compare?
Reproduction Viruses- only
reproduce with a host cell Cell- independent cell
division
Genetic Code Virus- DNA or RNA Cell- DNA
Growth and Development Virus- no Cell- yes,
cells increase in size and number
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Obtain and Use Energy Virus- no Cell- yes
Respond to the environmentVirus- no Cell- yes
Change over time Virus- yes Cell- yes
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What do you think? Are viruses alive?

• Give evidence to support this opinion
• YES
  NO