TERRY RICKS was thinking about Virus and keyed into cyberspace:
TR>     Alright Alan, I'm going to butt in here!  A virus is an obligate
TR>intracellular parasite.  It's bio-chemical make up includes one of
TR>four forms of nucleic acid:  single stranded DNA, double stranded
TR>DNA, single stranded RNA, or double stranded RNA.  The nucleic acid
TR>is contained inside a protein coat that is called a capsid.  The
TR>capsid is made up of protein groupings that are called capsomeres.
TR>Also kept inside the capsid are specific enzymes and control proteins
TR>that have the function of taking over metabolic control of the
TR>cellular host. 
TR>     To say that a virus, or more properly a single viral entity,
TR>called a virion, is metabolically inert is incorrect.  There is no
TR>enzymatic activity within the virion because there is no substrate
TR>present for the enzymes to react with.  The term dormant is more
TR>correct. 
TR>     While the "dormancy" exists inside the capsid, the capsid itself
TR>is very reactive.  Every known cellular form of life has a large
TR>variety of cell surface proteins.  Some of these react with food
TR>molecules, to bring those molecules within the cell.  Some of those
TR>proteins, unfortunately are receptor sites for viral capsid proteins.
TR>Whenever the correct capsid protein/cell surface protein come into
TR>contact covelent and hydrogen bonds are formed.  This then triggers
TR>the action by the cell of "pulling in" the virus in various ways (the
TR>mechanisms are very complex and can be discussed later if desired).
TR>     The effect is to "open" the capsid allowing the viral nucleic
TR>acid into the cytoplasm of the cell.  The various control proteins
TR>also come in and take over the metabolism of the host cell.  The
TR>result is the replication of the virus, producing millions to
TR>billions of virions.  Once all the virions are matured the host cell
TR>ruptures, releasing the virions into the environment.  The virus is
TR>metabolically active during the entire reproductive process and lives
TR>at the expense of the host (definition of a parasite).   This entire
TR>process from attachment of the virion to the rupture of the host cell
TR>is called the CYTOLYTIC CYCLE. 
TR>     Viruses are NOT cells, they are obligate intracellular
TR>parasites!  They are dormant until activated by binding to a
TR>receptive host.  They cause disease by the destruction of host cells,
TR>which disrupts the normal function of the organ that is made up of
TR>those host cells. 
TR>Terry A. Ricks, B.S., M.S., R.S.
TR>Istructor of Microbiology,
TR>San Antonio College, San Antonio, Texas
Hi Terry:
Excellent, well written and I am stealing it. :) Could you email me at 
my Juno address? Thanks.
                ===>The Voice of Reason<===
                     mark.probert@juno.com
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 * CMPQwk #1.4 * UNREGISTERED EVALUATION COPY
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