Viruses

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Viruses
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What Is A Virus

• A microscopic parasite that infects cells in
  biological organisms.

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Do Viruses Live

• Viruses are considered neither alive nor dead
• Viruses a HOST
• Can reproduce only by invading and controlling
  other cells as they lack the cellular machinery
  for self-reproduction
• Performs no cellular functions on its own.

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Viruses Are Parasites

• Viruses are parasites, meaning they cannot
  survive and thrive without a host or group of
  host cells.
• The hosts provide viruses with all the chemicals
  and molecules they need to survive and reproduce.
  
• Viruses are completely dependent upon other
  organisms to function.

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Physiology

• Consists of
• A strand of genetic material
• An outer protective protein coat called a CASPID
• Tail fibres that allow the virus to anchor onto
  host cells

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Viruses are Specific

• Specific viruses infect specific cells
• Example The Influenza Virus attacks the cells in
  the respiratory system and is responsible for flu
• Example Human Immunodeficiency Virus (HIV)
  attacks the white blood cells of the human immune
  system

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Virus Shapes

• Viruses can be classified by their shape
• Examples of virus shapes are
• Retrovirus
• Bacteriophage
• Andeovirus
• Pox Virus
• Tobacco Mosaic Virus

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Retrovirus

• HIV destroys white blood cells
• The loss of these cells impedes the ability of
  the immune system to fight infection
• AIDS occurs when the bodys immune system has
  collapsed and the body is open to infection

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Bacteriophage

• Bacteriophages are bacteria eaters.
• They attack and destroy bacteria

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Adenovirus

• The common cold is caused by the Rhinovirus
• Symptoms include coughing, sneezing, sore throat
  and a runny nose
• No cure for the common cold except for rest and
  lost of fluids

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Tobacco Mosaic Virus
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Pox Virus

• Small Pox
• Attacks blood vessels in the skin and around the
  mouth and throat
• Causes rashes and fluid filled blisters

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Ebola Virus
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Foot and Mouth Disease

• Highly contagious, from cattle and pigs

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SARS

• Severe Acute Respiratory Syndrome

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Replication

• There are generally 4 steps to replication
• Attachment and Entrance
• Synthesis of protein and genetic material
• Assembly of the new viruses
• Release of new virus particles

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Replication
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Replication
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Replication

• The process is known as the LYTIC CYCLE
• LYSIS The destruction or bursting open of a
  cell.
• This leads to the releasing of viruses from a
  cell.

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Replication

• Can be completed in as little as 25-45 min and
  can reproduce hundreds of new viruses under ideal
  lab conditions

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Lysogenic Cycle

• Viruses can lie dormant within any host or
  environment until the proper conditions for their
  activity are provided.
• LYSOGENY the dormant state of a virus
• The virus genetic material becomes integrated
  into cell and is replicated to all daughter cells
  until activated by a stimulus

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Activation

• Can be caused by environmental changes like
  temperature or pH
• Can be caused by changes in available nutrients
• The above can trigger the lytic cycle and new
  viruses are formed and released

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Viruses As Pathogens

• Viruses attack cells as they reproduce killing
  the host cells
• The destruction of these cells causes symptoms of
  diseases
• Antibiotics do nothing to stop viruses

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Vaccines

• Made from dead or weakened viral cells can
  stimulate the body to fight viruses