Reginald H. Garrett, Charles M. Grisham

The virus life cycle.
Viruses are mobile bits of genetic information encapsulated in a protein coat. The genetic material can be either DNA or RNA. Once this genetic material gains entry to its host cell, it takes over the host machinery for macromolecular synthesis and subverts it to the synthesis of viral-specific nucleic acids and proteins. These virus components are then assembled into mature virus particles that are released from the cell. Often, this parasitic cycle of virus infection leads to cell death and disease.

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  1. shinichi Post author


    by Reginald H. Garrett, Charles M. Grisham

    University of Virginia

    Part I – Molecular Components of Cells

    Chapter 1 – Chemistry Is the Logic of Biological Phenomena

    1.6 – Viruses Are Supramolecular Assemblies Acting as Cell Parasites

    Viruses are supramolecular complexes of nucleic acid, either DNA or RNA, encapsulated in a protein coat and, in some instances, surrounded by a membrane envelope. The bits of nucleic acid in viruses are, in reality, mobile elements of genetic information. The protein coat serves to protect the nucleic acid and allows it to gain entry to the cells that are its specific hosts. Viruses unique for all types of cells are known. Viruses infecting bacteria are called bacteriophages (“bacteria eaters”); different viruses infect animal cells and plant cells. Once the nucleic acid of a virus gains access to its specific host, it typically takes over the metabolic machinery of the host cell, diverting it to the production of virus particles. The host metabolic functions are subjugated to the synthesis of viral nucleic acid and proteins. Mature virus particles arise by encapsulating the nucleic acid within a protein coat called the capsid. Viruses are thus supramolecular assemblies that act as parasites of cells (Figure above).


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