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

The Results The filtered solution can still infect the tobacco plant.

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

The Discovery 1935—Wendell Stanley discovered the structure of a virus and proved that they are NOT a LIVING ORGANISM Nobel Prize winner. Extensive virus work..proved that they cause cancer.

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)

What is a Virus Parasitic (live off others) Disrupts the lives of the cells they invade Found in air, soil, and water

Structure of a virus capsid Nucleic acid Tail filaments

Influenza

Small pox

bacteriophage

Ebola

West Nile

HIV

Hepatitis C

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.

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.

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.

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.

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)

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

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.

How do retroviruses reproduce? They have a way to convert RNA to DNA. The DNA is copied by the cells they invade.

HIV’s structure

HIV attacks your body’s T cells

Virus docks by matching receptor shapes on host cell surface. HIV Host cell Matches the receptor on host

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