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Chapter 20.1 - Viruses Part 1 – Virus Structure and Function

Chapter 20.1 - Viruses

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Chapter 20.1 - Viruses. Part 1 – Virus Structure and Function. The Discovery of Viruses. Scientists were looking for the cause of a disease that was infecting TOBACCO plants. Causing tobacco mosaic disease. The Experiment. - PowerPoint PPT Presentation

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Page 1: Chapter 20.1 - Viruses

Chapter 20.1 - Viruses

Part 1 – Virus Structure and Function

Page 2: Chapter 20.1 - Viruses

The Discovery of Viruses

Scientists were looking for the cause of a disease that was

infecting TOBACCO plants.Causing tobacco mosaic

disease.

Page 3: Chapter 20.1 - Viruses

The Experiment

Filter a solution that causes the disease through a small filter that bacteria cannot get through.

Page 4: Chapter 20.1 - Viruses

The Results

The filtered solution can still infect the tobacco plant.

Page 5: Chapter 20.1 - Viruses

The Conclusion

The disease was caused by something smaller than a bacteria. They called it a virus.

Page 6: Chapter 20.1 - Viruses

The Discovery

1935—Wendell Stanley discovered the structure of a virus and proved that they are NOT a

LIVING ORGANISM. 1946 Nobel Prize

winner. Extensive virus work..proved that they cause cancer.

Page 7: Chapter 20.1 - Viruses

What is a Virus

Complex, submicroscopic, organic particle. (20 nm, have carbon)

Not cellular, no cell parts. Do not carry out life functions on

their own. Reproduce only inside a living cell

(host cell)

Page 8: Chapter 20.1 - Viruses

What is a Virus

Parasitic (live off others)Disrupts the lives of the

cells they invadeFound in air, soil, and water

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Structure of a virus capsid

Nucleic acid

Tail

filaments

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Influenza

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Small pox

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bacteriophage

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Ebola

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West Nile

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HIV

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Hepatitis C

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Structure of a Virus

A virus is a particle made up of a

nucleic acid core (either DNA

or RNA) and an outer protein coat called a capsid.

Some viruses also have an extra

outer layer called an envelope.

Page 18: Chapter 20.1 - Viruses

Role of Viruses

Most viruses are pathogens—

disease causing agents.Small pox, chicken pox, cold sores,

warts, AIDS, rabies, mumps, flu, measles, some forms of cancer and the common cold are caused by viruses.

Page 19: Chapter 20.1 - Viruses

How does the body handle viruses?

It is the job of the immune system to

fight diseases in the body. Your skin is one of the most important organs in this system because it keeps pathogens out of your body.

Once a virus is in your body, your main

defense is white blood cells. These cells are specialized to fight pathogens.

Page 20: Chapter 20.1 - Viruses

There are 2 main types of white blood

cells. T cells and B cells. B cells are normally more important for fighting viruses. Once a virus has entered your body, your B cells produce proteins called antibodies that will remember the virus and fight it off if the same virus enters your body again. This means that you normally never get the same viral infection twice.

Page 21: Chapter 20.1 - Viruses

Why do people have more than one cold or the flu more than once?

These viruses mutate quickly so your body doesn’t recognize them as the same thing.

(there are more than 200 strains of the common cold)

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Vaccine

Substance prepared from

inactive or weak viruses that cause your body to react and produce antibodies without making you sick.

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The HIV virus

HIV, the virus that causes AIDS, is in a class of viruses called retroviruses. These

viruses have RNA as their nucleic acid.

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How do retroviruses reproduce?

They have a way to convert RNA to DNA.

The DNA is copied by the cells they invade.

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HIV’s structure

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HIV attacks your body’s T cells

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Virus docks by matching receptor shapes on host cell surface.

HIV

Host cell

Matches the receptor on host

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Because HIV mutates very quickly, it is difficult to cure.