Viruses are simple organisms, formed by genetic material wrapped in a protective capsule.
Because they depend on other beings to carry out their activities and because of their ability to infect living organisms, viruses are considered mandatory intracellular parasites.
Check out below 9 general characteristics of viruses.
Viruses have no cells
Viruses are acellular beings, that is, they do not have a plasma membrane, cytoplasm or organelles.
Because they do not have cellular organization, many authors say that viruses are not living beings and, therefore, they are not included in the classification of domains (Archaea, Bacteria and Eukarya) and kingdoms (Monera, Protista, Fungi, Plantae and Animalia) of the nature.
However, those who defend that viruses are living beings take into account the presence of material genetic, their ability to reproduce, through a living cell, and the occurrence of mutations that make them to evolve.
Viruses are microscopic beings
The size of a virus ranges from 20 to 300 nm. They are smaller than bacteria, which are 0.2 to 1.5 μm in length, and that is why there are viruses that are parasites of these beings.
Because they have ultramicroscopic dimensions, electronic microscopes, which magnify an image by more than 100,000 times, are the devices used to visualize the structure of a virus.
Viruses have simple structure
The virus is made up of genetic material, most of which have DNA or RNA, coated with a protective protein capsule called a capsid.
Chemically, a virus is basically made up of proteins and nucleic acid. However, other components, such as carbohydrates and lipids, may be present in an envelope that surrounds the capsid.
Although they have a simple structure, viruses have different forms. See the image below for two forms of viral structure:
Viruses are intracellular parasites
As viruses do not have cells or their own metabolism, these beings develop their activities by invading a living cell to take advantage of its resources and multiply.
During a viral infection, the virus incorporates its genetic material into the infected cell's DNA.
The virus structure is formed by substances on its surface that recognize the type of cell it is able to penetrate and parasitize.
Viruses parasitize certain cell types
Viruses can be classified according to the types of organisms they infect. Check out some examples:
- animal virus
- plant virus
- Bacteriophages: viruses that infect bacteria
- Mycophages: Viruses that Infect Fungi
- Virophages: viruses that infect other viruses
Learn more about viruses: Bacteriophages and retrovirus
Viruses reproduce in living cells
Viruses need a living cell to reproduce, as they are not capable of multiplying on their own.
To invade a cell, viruses attach themselves to the cell wall and inject their genetic material, which is replicated while the cell performs its functions.
When they multiply, viruses break up the host cell and release new structures in a process called the lytic cycle. Viruses can also keep their genetic material in the parasitized cell and transmit to created cells in a mechanism called the lysogenic cycle.
Viruses cause diseases called viruses
While there are viruses that are not pathogens, many viruses are disease-causing. A disease caused by a virus is called a virus.
are examples of virus diseases:
- COVID-19: caused by the SARS-CoV-2 coronavirus
- AIDS: caused by the human immunodeficiency virus (HIV)
- Common Flu: Caused by the Influenza Virus
- Chickenpox: caused by the varicella zoster virus (VZV)
Viruses are diseases that are prevented with the use of a vaccine and many of them still do not have one.
Viruses can change and evolve
The genetic material of a virus can change genetically, producing genetic variability, through mutation or recombination.
When a virus mutates, its nucleic acid, DNA or RNA sequence changes. Recombination, on the other hand, is the result of exchanging stretches of genetic material.
Outside a cell, viruses are inert
When a virus is not found inside a cell of a living organism, the viral particle is called a virion.
A virion is the complete and isolated form of a virus, which can crystallize indefinitely.
Read more about the Virus and test your knowledge with Virus Exercises.
