Virus
From Wikipedia, the free encyclopedia
- This page is about biological viruses. For the computer term, see computer virus.
A virus is a small particle that can infect living organisms.
Viruses do not belong to any of the six kingdoms. They are seen by some as being nonliving structures and not alive. They do not meet all the requirements for being classified as a living organism because viruses cannot reproduce by themselves. Some people still believe that viruses are alive, especially microbiologists.
Viruses are much smaller than bacteria. Their size is at the molecular level. They can only be seen with an electron microscope. A virus has a simple structure. It has no internal cellular structure, no cell wall or cell membrane. They are made of only a protein coat that holds a coiled string of nucleic acid. In order to be classified a parasite, a virus must be alive. There are some people who would classify a virus as a parasite, and some who would not.
They have the following characteristics:
- Infectious particles, causing many types of disease;
- Contain nucleic acid core DNA or RNA;
- Surrounded by a protective protein coat;
- Only kingdom of living things without subcategories.
When the host cell has finished making more viruses, it undergoes lysis, or breaks apart. The viruses are released and are then able to infect other cells. Viruses can remain intact for thousands of years, and will infect cells when the time and conditions are right.
