Causers of numerous diseases, the virus they are very much feared by everyone. Acellular, measuring around 200 nm and can only be seen with an electron microscope. Some scientists don't consider them to be living beings., as they do not have the ability to reproduce on their own, depending on any living cell of animals, plants or bacteria. Inside, we find a protein capsule called capsid. Inside the capsid, there are nucleic acid, which can be DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) or both types.
→ Prions and Viroids
When we study viruses, we cannot forget to mention two infectious agents that are much simpler than them: prions and viroids. You prions they are infectious protein particles that, once in the bloodstream, accumulate in nerve cells, causing their death. They cause encephalopathies such as mad cow disease. You viroids are formed by RNA and affect only plants.
→ Virus reproductive cycle
Viruses only infect cells that have a certain specificity between the cell's lipoprotein plasma membrane and the virus's capsid proteins.
Viruses have two types of reproductive cycles: the lytic cycle and the lysogenic cycle.At the lithic cycle, the cell is infected and the viruses command the entire reproductive process inside it, leaving the cell completely inactive. The virus takes over the cell's metabolism and can produce up to 200 viruses, causing cell lysis. The viruses that have been produced attack other cells and start the cycle all over again.
At the lysogenic cycle, the virus nucleic acid enters the cell nucleus and incorporates with the cellular nucleic acid. The virus then begins to participate in cell divisions. As the cell undergoes mitosis, the viral load is passed on to the daughter cells, infecting the entire organism.
→ viral infections
The most studied viruses known to attack only bacteria are called bacteriophages. These viruses have only viral DNA inside them.
There are viruses that attack plants and cause damage to agriculture. Other viruses attack animals and are responsible for numerous deaths and epidemics around the world. Some diseases that are caused by viruses they are: the flu or cold, polio, anger, hepatitis A, B, Ç, D and is, herpes, dengue, yellow fever, measles, rubella, chickenpox, mumps and AIDS.
When the virus enters the body, it starts to produce antibodies to fight it. The organism starts to "recognise" (immunological memory) this virus and, if the person comes in contact with it again, the body automatically fights it.
For some diseases that are caused by viruses, it is possible to produce vaccines. The vaccine is nothing more than dead or attenuated viruses that, in contact with the organism, induce the production of antibodies. If the body comes into contact with that type of virus, it will already have specific antibodies to fight them and the body will not be harmed.
By Paula Louredo
Graduated in Biology
Source: Brazil School - https://brasilescola.uol.com.br/biologia/caracteristicas-gerais-dos-virus.htm