Great question!! There are many different
kinds of viruses, many that are harmless to us
and a few that can make you very sick.
Viruses can NOT multiply by themselves, they
need to use many parts of a host cell to help
them multiply. All a virus is made of is genetic
information wrapped in a shell. Depending on
what type of genetic information the virus
contains, there are two types of viruses: RNA
viruses and DNA viruses. DNA viruses carry their
genetic information as DNA that can be
immediately turned into information by the host
cell. RNA viruses are not as simple. First an
RNA virus must use the host cell to turn its RNA
into DNA which must then be turned into
information, and this is all done using the host
cell's machinery. Viruses can not do any of this
on their own.
Both DNA and RNA viruses encounter many host
cell defenses during infection. Our bodies have
become very good at detecting and killing
viruses because we are exposed to so many of
them. Cells can detect viruses both inside and
outside of the cell and then alert other cells
to help fight the infection. Our bodies do
produce very small proteins called "defensins"
that protect us from microbes like bacteria,
viruses and fungi. Defensins work by poking
holes in the membrane of a virus (or bacteria)
and making it leak water and die. They are
important parts of our immune system.
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