Viruses Enciphered by a Protein Shell
The human immunodeficiency virus (HIV) is a retrovirus that attacks the T-cells of the immune system. A virus is an infectious viral particle which contains an RNA or DNA sequence enclosed in a living protein shell. When a virus attacks a healthy cell, it surgically removes its protective protein coating and executes its genetic code to directly infect and duplicate itself in the target cell. In turn, T-cells recognize this virus as a foreign entity and initiate a response called antiviral antibodies in an attempt to stop the virus from invading the healthy cells.
Enveloped viruses are very small in comparison to the virus’ outer membrane, which is the layer of lipids, proteins, and other substances that surround the virus inside a cell. Enveloped viruses usually end up inside an uninfected cell that is sensitive to their activities and unable to regulate its growth due to lack of vital receptors. Once the virus gets inside the cell, it triggers an alarm reaction that causes extensive damage and inflammation.
Unlike viruses, bacteria can remain alive outside of a living cell for periods of time. Most bacteria are able to exist as single-celled colonies on the surfaces of living cells such as the gills and the intestines. However, when a new cell is generated, the bacteria release enzymes that help them divide into more cells and spread out to other areas of the body. These newly populated cells eventually become potential sites for the production of toxins that can invade other healthy cells, damaging them and causing illness.
Because bacteria and virus cannot survive without a protein shell, they tend to form aggregates or colonies on the surface of a cell. However, some viruses are able to infect living cells without any sort of protein shell and therefore infect the cellular membranes. The most damaging kind of virus is the capsid. This virus invades a cell through a fluid-filled cell membrane. It typically inserts its genetic material and establishes a viral protein shell around this genetic material to trigger a biological response in the infected cell. This virus is usually accompanied by a replication process that causes it to replicate rapidly in the infected cells.
While some viruses and bacteria are part of the complex cellular machinery that constitutes a living cell, there are also viruses that break down genetic material inside a cell without triggering a biological response. These types of viruses are called nonfunctional viruses because they have no ability to replicate themselves or spread to other living cells. Genetically encoded RNAs (genetic RNA) that cannot be read by conventional laboratory methods are one type of nonfunctional virus.
A viral capsid is any of a number of protein shells that are secreted by a virus in order to bind to a specific host cell. There are generally two types of viruses: retroviruses and bacteriophages. Retroviruses are enveloped capsids that insert themselves into the genome of a living cell. Bacteria acquire their capsid from a different virus that is then reactivated and released into the environment. The viruses that engage in destructive intrusions into a host’s cells are known as viriocapsids.