viruses

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MEWAR UNIVERSITY

SUbjEcT: MIcRobIologY

NAME : pEER zAdA SUhAIl

TopIc: VIRUSES

pRESENTEd To :MR.NAVEd SIR

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We have all gotten viruses…

from bacteria, plants to animals.

Viruses cause colds, flu, warts and diseases such as measles, AIDS and cancer.

AND not all viruses are harmful to humans.

BUT not all viruses cause diseases,

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WHAT IS A VIRUS?

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A VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID.

DNA CAPSID

VIRUS

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Why are some viruses harmful?

Virus invades cell

Virus forces cell to make copies of virus

Eventually so many copies are made, the cell explodes,releasing all of the new viruses

When your cells make viruses instead of operating normally, YOU get sick

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DISEASE VIRUSES

AIDS HIV

WartHerpes Simplex Virus

Flu Influenza

Measles Morbillivirus .

Cancer Hepatitis B

Examples of some viral diseases:

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Who do viruses infect?

• Viruses infect Bacteria– These viruses are called bacteriophages

• Viruses infect Plants– One example is the Tobacco Mosaic Virus

• Viruses infect Animals– One example is the common cold

Viruses usually infect a specific host including:

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let’s look at the defining ProPerties of viruses

• Viruses are parasites that invade cells• Viruses have either DNA (Deoxyribose

Nucleic Acid) or RNA (Ribonucleic Acid)• Viruses direct the synthesis of new

virus within a host cell.• Newly made viruses infect other cells.

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How small is a virus?

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If a cell was the size of your classroom, then an average virus would be the size of a softball.

Viruses range in size from 20 nanometers (nm) – 250 nanometers (nm)

1 nm = 0.00000004 inches

10-5 m10-6 m

10-7 m

10-8 m

10-9 m

10-10 m

0 m

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Go five more feet!

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How do viruses replicate?

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Replication Phases

V - Release- Assembly of virus

DNA and protein coat into whole new viruses

- Leaving the cell

Phase I

Phase II

Phase IV Phase VPhase III

I, II, III - Viruses enter cell- Attachment to cell membrane- Penetration inside cell- Losing virus protein coat

IV - Replication- Tricks cell into making

more viral DNA- Tricks cell into

making viral protein coat

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The concept of a virus as an organism challenges the way we define life:

* Viruses do not breathe.* Viruses do not metabolize.* Viruses do not grow.* However, they do reproduce.

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Are Viruses Living?Create a table where one column represent properties of living organisms and the second column represent properties of a virus.

Properties of Living Organisms

Properties of Viruses

Breathes (respires) Doesn’t breathe

Metabolizes Doesn’t metabolize

Grows Doesn’t grow

Reproduces Reproduces

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The End! And Review• Viruses are very simple: a shell containing

either DNA or RNA.They infect by hijacking cells’ machinery to

force them to make more viruses.• Viruses are tiny, even compared to a cell.• Some viruses may prove useful in gene

therapy as natural carriers of DNA that was specially designed to be good for a particular reason.

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