Viruses3 - various viruses that cause hepatitis invade only...

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Viruses: a Group of Intracellular Parasites Viruses are obligate intracellular parasites that can be maintained only inside living cells. Whern we refer to something as "obligate" that indicates that the virus (in this case) must do or behave in the specified manner. Since viruses are obligate intraellular parasites, the term conveys the idea that viruses must carry out their reproduction by parasitizing a host cell. They cannot multiply outside a living cell, they can only replicate inside of a specific host. Animal viruses in laboratories are raised in live chick embryos or propagated in cell tissue culture. Viruses infect all sorts of cells, from bacteria to human cells, but for the most part tend to be host specific. For example, the tobacco mosaic virus infects certain plants; the rabies virus infects only mammals; and the AIDS virus, HIV, infects only certain human blood cells. The
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Unformatted text preview: various viruses that cause hepatitis invade only liver tissues, while the polio virus only reproduces in spinal nerve cells. Figure 5 shows a bacterial virus, as well as an HIV human virus. Viruses gain entry and are specific to a particular host cell because portions of the capsid (or spikes of the envelope) adhere to specific receptor sites on host cell plasma membrane. Their nucleic acid then enters the cell, where the viral genome codes for production of protein units in the capsid. Bacteriophages invade the host cell, take over the cell, and begin replicating viruses, eventually lysing or bursting the host cell, releasing the new viruses to infect additional cells. Figure 6 illustrates a typical T bacteriophage, as well as several of these viruses being assembled in a host....
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Viruses3 - various viruses that cause hepatitis invade only...

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