Do you remember the last time you caught a fever, cold, or a sore throat? Chances are the culprit are the most infinitesimal creature on Earth – viruses. They can infect all living things, be it from plants, animals, bacteria, archaea, and even other viruses. These tiny invaders target the cells and use them to replicate themselves.
While cells can thrive to eat, grow, and reproduce, viruses are nothing like them. If you looked at a virus, you would notice that viruses are seemingly just like particles. Each particle is called a virion, which doesn’t have the ability to grow or multiply by themselves.
The size of these particles stretches around one-millionth of an inch, making the majority of viruses impossible to see with a simple light microscope. They are so tiny that they can only be seen through an electron microscope. Generally, viruses are smaller than bacterias though there are giant viruses that were discovered in 2003, which were about the same size.
Each virion is composed of the following components: nucleic acid, capsid, and the lipid membrane.
Nucleic acid – which can either be DNA or RNA, contains sets of genetic directions, on how it would reproduce or replicate itself. It serves as the virion’s guide on how it could continue its existence.
Capsid – is the protein coat that envelopes the nucleic acid that functions as its shell or shield, protecting the genetic material.
Lipid Membrane – is a fat layer that can be found in some viruses, which surrounds the capsid. Viruses that have such layers are regarded as enveloped viruses. Others that do not possess one are called naked viruses.
Viruses differ immensely in their shape or appearance. They can be classified into four groups based on shape: isometric, filamentous, enveloped, and head and tail.
Isometric viruses tend to be spherical, such as the poliovirus and the herpes virus. Filamentous viruses are long and cylindrical, like most plant viruses. Meanwhile, enveloped viruses possess capsids like HIV. Lastly, head and tail viruses have a spherical head, and filamentous body, and commonly affects bacterias. Some viruses don’t fall on any of the given categories and may appear seemingly like a popcorn ball or spider. Such viruses that have more complicated structures are called complex viruses.
But, how do viruses work? Viruses don’t have the same number of enzymes that human cells or bacteria have to fulfill chemical reactions it needs they need to live. These tiny invaders are only limited to a single or two of these enzymes wherein they store their genetic directions. For viruses to live, they need to find a host cell where they can ‘reside’ and replicate itself.
Without any host cell, a virus won’t be able to function, which is why some people regard them as a non-living entity. However, as viruses do incredible things once it finds a host, scientists agree that they are alive – caught between the fine line that divides entities from non-living entities.
While simple as they seem, viruses can take over more complicated cells. In order to get inside a host cell, they play some trickery, letting the cell think that it needs the virus within it. Cells are surrounded by receptors with specific shapes that match the form of nutrients. Once they fit, the cell absorbs the nutrients inside.
What viruses do is disguise like a nutrient. Its coating appears like the nutrient the cells require. Once the cell is tricked, it pulls the virus inside, making it infected by the virus.
Once the virus is able to penetrate the cells, it starts doing its work. It adds its genome or its hereditary information to the cell. The cell, thinking that it needs the virus, follows the genetic instruction incorporated by the invader and begins producing virus parts. These parts will then merge to form a single virus and break out from the cell. Each new virion will look for another host cell, repeating the process and spreading the infection.