A basic virology lesson. What is a Virus? A basic virology lesson.

Viruses are strange life forms. They have only one type of nucleic acid (DNA or RNA) They reproduce from nucleic acid. They have no metabolic enzymes. They are completely dependent on their host cell.

Definitions Viral particle: one tiny individual virus creature. It is so small that it is the size of a large molecule Capsid: The nucleic acids within the viral particles surrounded by a protein coat and a fatty envelope. The capsid proteins are crucial to the virus’ ability to attach and infect the host cell DNA: Serves as the blueprint of instructions on how to make different proteins in a cell. It enables the cell to live and function within a body.

Messenger RNA: When it comes time to make a protein, a DNA segment “unzips” its double strands allowing messenger RNA to enter and bind. Messenger RNA then leaves the cell nucleus and travels out into the cell’s cytoplasm where the message is read by the ribosomes. Transcription: The act of messenger RNA taking down the protein code from the original DNA segment. Translation: The act of producing a protein from the segment of messenger RNA using transfer RNA . It is performed by the ribosomes.

Viral infections The goal of the viral particle is to attach to a host cell and somehow inject its nucleic acids into the host cell. In order to accomplish this a capsid is needed. The capsid is very specific as to what host cell it can attach to. Specific for species. (dog, cat, human) and specific for cell type (blood cell, intestinal, brain etc.) Once the viral particle has injected its nucleic acids into the host cell, the next goal is to manufacture messenger RNA for the cell to translate into protein. These new proteins produced will shut down the cell’s normal function and convert the cell into a factory for viral particle production.

The Host Cell is Doomed! Viral proteins will shut down normal cell function and dedicate the cell to the production of viral capsid and viral DNA Soon the host cell is a little more than a bag of virus. The viral particles either bud off the surface of the host cell or the host cell explodes leaving millions of new viral particles to seek new host cells.

The only way to stop a virus is for the immune system to recognize the infected cell early and destroy it before virus production becomes too advanced.