BIOL 4140 Lecture Notes - Lecture 25: Coevolution, Intracellular Parasite, David Baltimore
Document Summary
A virus is a small infectious agent that comes in a variety of shapes and sizes, yet in general, all include a capsid, polymerase, genome, and sometimes an envelope. A virus needs a host cell because it lacks the machinery needed to replicate its own genome. Without the replication machinery of its host cell, a virus would not be able to survive and reproduce. Viruses will invade any form of life in order to survive. Therefore, viruses are considered obligate intracellular parasites; they feed on their host cells in order to assure their own survival. In this, viruses are in constant competition with their host cell for the propagation of their own genetic material. All in all, viruses are absolutely dependent on their host for survival. Considering viruses are unable to survive outside their host cell, it has long been debated if viruses are in fact living or not.
