Viruses

Alive or not?

There are many viruses that affect humans. Here are a few of them.

The AIDS Virus

Herpes simplex virus

Smallpox virus

Different types of Influenza viruses

Measles virus

Ebola Virus

Viruses attack specific species and often specific cells.A virus that would affect a human would not affect different organism.

Bacteriaphage viruses attack only bacteria

Tobacco Mosiac virusAttacks tobacco plants

Viruses remained undiscovered for so long because they are very small.

Human Skin CellBacteriaViruses

The very first virus discovered on the 12th February 1892 by Dmitri Iwanowsk (1864-1920), a Russian botanist. While studying mosiac tobacco disease, he found that the agent causing the disease

was small enough for pass though ceramic filter that are small enough to trap all bacteria. This is generally accepted as the beginning of Virology.

So what is a virus?The virus is made up of2 basic structures: 1. A core of DNA or RNA 2. A protein coat surrounding the DNA or RNA called a capsidSometimes they have tail fibers that help themattach to a host cell.

Viral reproduction is quite fascinating!

1. The virus

attaches to the

membrane of a

host cell.

2. The virus injects its genetic material into the host cell.

3.The viral DNA is replicated by the host cell.

4. The viral DNA and protein coats are produced by the host cell.

5. The parts of the virus assemble

6. Viral enzymes break down the membrane causing the host cell to split open.Now the new viruses infect neighboring cells.

So how can you fight a viral infection?There are no medications or drugs that can help

you get rid of a virus.

Antibodies are produced in the blood (yellow) which are specific to the attacking virus (green)

The antibodies disable the virus but only after you have felt the affects of the illness

Prevention of Viruses Viral infections can be prevented with a

vaccine. A vaccine is a liquid that contains a

weakened form of the virus (usually the protein coat)

This fools the body into producing antibodies so that when the real virus attacks, the body is ready to disable it.

Types of Vaccinations you have received. Tetanus Influenza Polio Mumps Measles Rubella Chicken pox Hepatitis

How to avoid getting and spreading the flu virus

Wash your hands often

Get plenty Of rest Drink lots of water

Get a flu shotAvoid sick people

Don’t eat at buffets Eat healthy foods

Like fruits and vegetables

How do viruses and cells compare? Reproduction:Viruses- only reproduce with a host cellCell- independent cell division

Genetic Code:Virus- DNA or RNACell- DNAGrowth and Development:

Virus- noCell- yes, cells increase in size and number

Obtain and Use Energy:Virus- noCell- yes

Respond to the environment:Virus- noCell- yes

Change over time:Virus- yesCell- yes

What do you think? Are viruses alive?

Give evidence to support this opinion:

YES NO