This Picture is of a bacteriophage, phage means virus and bacteria is the host.This virus is also kn...
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This Picture is of a bacteriophage, phage means virus and bacteria is the host.This virus is also known as T4. Viruses have a covering made of protein which is called a capsid.

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PowerPoint Slideshow about 'Viruses' - Melvin


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This Picture is of a bacteriophage, phage means virus and bacteria is the host.This virus is also known as T4

Viruses have a covering made of protein which is called a capsid

In their center is either DNA or RNA. When DNA or RNA is injected into the host cell it makes the host cell produce more viruses. Eventually the host cell dies and releases millions of copies of the original virus.

Are viruses alive? Yes and No They are however very efficient parasites.


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This is how a T4 virus infects a cell. The virus takes over the cell until the cell bursts releasing more viruses.

This is known as a lytic infection because the cell is destroyed

Viruses are specific for the host they infect Example:

Rabies - Mammals

Tobacco Mosaic (TMV) - Plants

Chicken pox - humans


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The difference Between a Lytic virus and a Lysogenic virus is a lysogenic virus becomes part of the host’s DNA and doesn’t destroy the host cell but exists as a prophage until a time of stress then it reproduces and kills the host.

Retro viruses are Lysogenic viruses except the inner core is made of RNA. Once in the host RNA is converted by an enzyme ( reverse transcriptase) into DNA then the virus becomes a prophage. Herpes and Chicken pox are retro viruses.


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A Bacteria is known as a Prokaryote because inside its cell there is no nucleus and the DNA is exposed and circular.

Bacteria move by means of a flagellum which is made of a protein called Flagellin

Bacteria do not have any organelles only ribosomes. They have a cell wall, a cell membrane, and some have a hard outside shell called a capsule.

Some bacteria will stain with a purple dye and they are called Gram +

Those that do not stain purple will usually stain red and they are called Gram -


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Most bacteria are known as Eubacteria or true bacteria. However there are some bacteria which are peculiar and are called Archaebacteria. These bacteria live in areas like the Hot springs and the deep sea vents.

Bacteria have three different shapes:

Round - Cocci If there are two it has the prefix diplo

Rod - Basillus If they are in a chain the prefix is strepto

Spiral - Spirrilum If they are in a group it is called Staphlo

Thus Streptococcus is a long chain of round bacteria


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Bacteria are helpful because they make things like yogurt, sauerkraut, and cheese.

Bacteria are helpful because they are decomposers which return nutrients to the soil.

Bacteria are bad because they cause diseases like Turberculosis, Gohnorria and Strep throat. Lucky for us bacteria can be killed by antibiotics.


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