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Chapter 20: Viruses and Bacteria. pp. 454-461, 470-471. Overview…. What is a virus? The anatomy of a virus. Types of viruses. Diseases caused by viruses. Vaccinations. What is a Virus?. Living or Non-living? Viruses were once thought to be a type of bacteria . Tobacco Mosaic Virus

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Presentation Transcript
  • What is a virus?
  • The anatomy of a virus.
  • Types of viruses.
  • Diseases caused by viruses.
  • Vaccinations.
what is a virus
What is a Virus?
  • Living or Non-living?
    • Viruses were once thought to be a type of bacteria.
  • Tobacco Mosaic Virus
    • Discovered in 1933 by Wendell Stanley.
    • Isolated crystals were found to be chemical matter rather than bacteria.
what is a virus4
What is a Virus?
  • What is this chemical matter?
    • A virus consists only of nucleic acid and protein.
  • Viruses require living cells for reproduction, making them non-living organisms.
  • Definition of a Virus.
    • A non-living strand of nucleic acid encased in a proteincoat that can infect cells and replicate within them.

What are the two main molecular components of a virus…

Nucleic Acid & Protein

anatomy of a virus
Anatomy of a Virus
  • Most viruses have a protein sheath called a capsid, which surrounds the core of the virus.
  • The capsid in some viruses is surrounded by a lipid membrane called an envelope. The envelope allows viruses to gain entry into cells.
  • The envelope contains glycoproteins (proteins with carbohydrate molecules attached)
  • The nucleic acid found in viruses is DNA or RNA.
anatomy of a virus7
Anatomy of a Virus

Enveloped virus (HIV)

anatomy of a virus8
Anatomy of a Virus

Complex virus (Bacteriophage)


Name a structure on a typical virus…

  • Capsid
  • Envelope
  • Protein/Glycoprotein
  • Nucleic Acid
  • Tail
  • Sheath
types of viruses
Types of Viruses
  • Viruses come in various shapes and sizes (20-300nm).
  • There are four basic types of viruses:
    • Helical viruses
    • Icosahedral viruses
    • Enveloped viruses
    • Complex viruses
diseases caused by viruses
Diseases Caused by Viruses
  • Tobacco Mosaic Virus (TMV)
    • A helical virus.
diseases caused by viruses12
Diseases Caused by Viruses
  • Various strains.
  • Infects various crops besides tobacco.
diseases caused by viruses13
Diseases Caused by Viruses
  • Hepatitis B Virus
    • An icosahedral virus.
    • Effects the liver and can cause inflammation, vomiting, jaundice, but rarely death.
    • Can lead to cirrhosis or even liver cancer.
diseases caused by viruses14
Diseases Caused by Viruses
  • Acquired Immune Deficiency Syndrome (AIDS)
    • Caused by Human Immunodeficiency Virus (HIV).
    • A type of enveloped virus.
diseases caused by viruses15
Diseases Caused by Viruses
  • Chickenpox
    • A type of complex virus.
    • “Pox” = curse.
in the news
In the News…
  • Avian Bird Flu
    • Virus that some birds are adapted to, while others are not.
    • Can be lethal to unadapted birds.
    • Can infect humans in some cases.