A virus is a microscopic life form that requires a host organism to live and reproduce. They are infectious and often cause unpleasant and long lasting symptoms. There are over 5,000 viruses described in detail and millions of different types in the world today. These infect not only humans, but other animals, plants and bacteria. They come in many different shapes and can appear as a simple ball shaped organism to a complex spider like organism.
How to Viruses Reproduce?
Viruses tread the thin line between being a living organism and being a non-living organism. This is due to the simplicity of their make up. A virus consist of three parts; Nucleic acid, a coat of protein and a lipid membrane. The Nucleic acid contains a set of genetic instructions or the viruses DNA, the protein coat surrounds and protects that DNA. Some viruses also have the lipid membrane as another form of protection, but not all do. Due to this simplicity and the fact that viruses are acellular, they are not able to live or reproduce outside of a living host. Most viruses go through six stages to reproduce, although it does vary from virus to virus.
Stage One: Attachment
In the first stage the virus attaches itself to the surface of the cell wall of the host organism. Each virus has a specific receptor that it needs to reproduce so this determines what type of cell it must attach to. When the virus attaches it creates a merger of the protein coat and the cell wall.
Stage Two: Penetration
Once the virus has attached itself to the surface of the cell membrane it effectively creates an opening for virions to enter the cell. This is what is known as viral infection. It may also inject its nucleic acid into the host cell where it replicates.
Stage Three: Uncoating
In this stage the protein coating is dissolved allowing the nucleic acid that contains the DNA to infect the cell that the virus has penetrated.
Stage Four: Replication
At this stage the nucleic acid uses the host cell to replicate itself creating more viruses.
Stage Five: Self-Assembly
In this stage the different sections of the virus come together to form a complete virus.
Stage Six: Released
After the virus has gained its form, it is released from the host cell by bursting the cell membrane. This kills the cell and is what causes the symptoms of viral infection. Some virus DNA stays within the cell and each time the cell goes through mitosis (cell division) the viral agent is also replicated. Once the virus is free of the cell it repeats the process and infects other healthy cells.