When talking about living beings, no kind of discussion is generated by indicating that an animal or a plant is living beings. The same thing happens with fungi, algae and bacteria. But When we get to the viruses, things change And these infectious agents break the rules.
First, they are not cells, but rather simple protein structures that contain genetic material inside. Second, their only way to reproduce is by infecting cells, to use their tools for this purpose. And third, they do not need to obtain any kind of energy, since they do not require maintenance.
Outside of the discussion of whether they are considered living beings or not, there is variety in both their content and their structures, which has made it possible to identify different types of viruses The importance of knowing them better has to do with their role as causes of diseases in living beings, some more serious than others. Better knowledge helps in the prevention and treatment of these.
Viruses stand out above anything else for being very simple in composition. It is a protein structure, with greater or lesser complexity depending on the class, which aims protect the genetic material it carries while acting as its vehicle.
Capsid
The main structure that all viruses have is the capsid. Made up of a set of protein units called capsomers, when it stores the genetic content inside it changes to be called a nucleocapsid. The shape that this piece takes is one of the criteria for identifying types of viruses.
The nucleocapsid may have icosahedral symmetry, which is observed as a spherical shape; a helical symmetry, which is rod-shaped or tubular; and of complex symmetry, apart from the nucleocapsid, it has an attached protein structure that is collectively called the tail, which acts as a support to facilitate the insertion of the content into a host.
Envelope
Independently of this, some viruses may have a second layer, called the envelope, which is made up of lipids. Their presence or absence is another criterion used to classify them.
Types of viruses according to their genetic material
Unlike cells, the genetic content of these infectious agents is extremely varied in classes and configurations, making it a good point to use in taxonomy. Roughly, There are two main types of viruses: those that contain DNA as genetic material and those that store their information in the form of RNA.
DNA viruses
Types of DNA viruses They have a small chain of nucleic acids which can be both single-stranded and double-stranded, that is, in one chain or in two. Furthermore, it can be circular or linear, it all depends on what virus we are talking about. They are the most common viruses to find. For example, the cause of herpes (Herpesviridae) has genetic content that is in the form of linear double-stranded DNA.
RNA viruses
As you can imagine, the only difference between RNA viruses and others is in the nucleic acids. The same thing happens: it can be made up of one or two chains, and be linear or circular. A well-known example is the retrovirus family (Retroviridae), among the diseases that can cause AIDS. In this case, it presents its genetic material in the form of linear single-stranded RNA.
Not all types of viruses have affinity for the same organisms or cells. In other words, some viruses only affect animals and not plants Thanks to this, it can be used as a criterion for classification. In this case it focuses on which is its guest, there being three groups:
The case of coronaviruses
Recently, The term “coronavirus” has become world famous in the wake of the global pandemic caused by one of the virus species belonging to this category. This is severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes the disease called COVID-19, pneumonia with a relatively high mortality rate in humans. This pathogen variant was discovered in the Chinese city of Wuhan, but since this point of origin, it has mutated several times.
But beyond this case, coronaviruses are types of viruses that have been known for a long time and that in the taxonomy used to classify these biological entities are in the family of Coronaviridaeso they are considered to constitute a subfamily.
One of the characteristics of these species is that They are the RNA viruses with a longer genome, and by the protuberances on its rounded surface, which make it appear to be wearing a spiked crown when viewed through a microscope. On the other hand, most coronavirus species do not pose a significant danger to most people.
How do they work?
I couldn’t finish this article without explaining how viruses work in a generic way. The viron (mature form of the virus) locates a host cell, managing to introduce its genetic content inside it. This material inserts into the DNA of the nucleus, so the cell can transcribe its information and translate it into proteins that configure the capsid and so on. It is also possible to replicate the genes of the virus, in order to introduce it into the new capsids and form new virions that leave the infected cell.
This is a generic way of talking about the life cycle of viruses; There are many variables. Examples cited, such as retroviruses, first have to transcribe their RNA content into DNA and manufacture the complementary strand before they can be inserted, since cells contain their genetic material in the form of double-stranded DNA.
The cause of viruses generating diseases is due to this insertion into the cell’s DNA, which can translocate genes, in addition to allow them to take control of the cell for its proliferation, causing it to not work correctly.
