Download Viruses!!

Viruses!!
living or non-living?
vi·rus
A virus is a small infectious agent that replicates inside the living cells of
other organisms. Viruses can infect all types of life forms, from animals and
plants to bacteria and archaea. Viruses are found in almost every
ecosystem on Earth and are the most abundant type of biological entity!!
Viruses:
● need to be inside a living organism to reproduce themselves
● have no metabolism outside of the cell
● have no cells parts (organelles)
● are composed only of a nucleic acid (DNA or RNA) inside a protein
viral reproduction
Lytic cycle
http://sites.fas.harvard.edu/~biotext/animations/
lyticcycle.html
baby viruses
After contacting a host cell, a virus will insert genetic material into the host and take over that host's
functions. The cell, now infected, continues to reproduce, but it reproduces more viral protein and
genetic material instead of its usual products.
Viral reproduction:
●
a virus attaches to a host cell
baby viruses
Viral reproduction:
●
a virus attaches to a host cell
●
the virus injects the cell with its nucleic acid
baby viruses
Viral reproduction:
●
a virus attaches to a host cell
●
the virus injects the cell with its nucleic acid
●
the viral nucleic acid commands the cell to make more viral protein and nucleic
acid
baby viruses
Viral reproduction:
●
a virus attaches to a host cell
●
the virus injects the cell with its nucleic acid
●
the viral nucleic acid commands the cell to make more viral protein and nucleic acid
●
the cell ruptures, releasing hundreds of new viruses
Retroviruses
These are viruses that store their genetic information as RNA instead of
DNA.
One example is HIV (Human Immunodeficiency Virus)
how do viruses move (spread)?
Viruses may spread vertically (from mother to child) or horizontally (from person to person). A virus's
ability to spread depends on the makeup of the virus.
Some viruses can spread by simple contact, exchanges of saliva, coughing, or sneezing. Some
require sexual contact, while others spread via contaminated food or water. Still other viruses require
an insect like a mosquito to carry the virus from person to person.
what are viruses made of?
Virus particles (known as virions) consist of two or three parts:
i) the genetic material made from either DNA or RNA
ii) a protein coat that protects these genes; and in some cases
iii) an envelope of lipids that surrounds the protein coat when they are outside a cell.
metabolism
Viruses do not have their own metabolism, and require a host cell to
make new products. They therefore cannot naturally reproduce
outside a host cell– although bacterial species such as rickettsia and
chlamydia are considered living organisms despite the same limitation
Although viruses cause disruption of healthy homeostasis, resulting in
disease, they may exist relatively harmlessly within an organism. An
example would include the ability of the herpes simplex virus, which
causes cold sores, to remain in a dormant state within the human
body.