All organisms are made up of cells - the smallest structural and functional units of the structure. But there are also non-cellular forms of life: viruses and bacteriophages. What features of the structure allowed them to occupy their worthy niche among the kingdoms of wildlife? Let's find out more.
Viruses are non-cellular life forms
The name of these organisms is translated from Greek as "poison". And this is no coincidence. No one has ever seen them with the naked eye, but almost everyone has suffered their influence. After all, flu symptoms in the winter are knocking at our house without asking.
It is now known that viruses are non-cellular life forms. The biology of these organisms remained a mystery for many centuries. And only at the end of the 19th century, the Russian physiologist Dmitry Iosifovich Ivanovsky proved that viruses are the causative agents of many diseases. A scientist was examining a tobacco plant that had been affected by tobacco mosaic. He noticed that if the juice of a diseased plant penetrates into a he althy one,then he will be defeated.
The structure of viruses
Why are viruses non-cellular life forms? The answer is simple: their body is not made up of cells. It is a nucleic acid molecule surrounded by a protein coat called a capsid. Distinguish between DNA and RNA viruses.
Depending on the structural features, non-cellular life forms - viruses - are divided into simple and complex. The former have a classical structure of nucleic acids and proteins. And the latter, during assembly, additionally attach a part of the plasma membrane. It acts as an additional protective shell.
Why are they alive?
So, viruses are non-cellular life forms, they do not have the usual membrane and organelles - permanent cellular structures that perform certain functions. How are they classified as living organisms? They are capable of reproduction. Moreover, being outside the host organism, they do not show any signs of existence. As soon as the virus is in the cell, it begins to synthesize its proteins. At the same time, the process of suppressing the production of the body's own protein molecules begins.
Viral proteins act as enzymes - biologically active substances. They accelerate the reproduction of nucleic acids. Thus, the number of foreign particles increases, and the own synthesis processes stop. As a result, the body becomes ill, because the virus needs energy and organic substances from the host cells to start the process of reproduction.
Bacteriophages
Viruses are non-cellular life forms that can parasitize in any organism. And single-celled prokaryotic bacteria are no exception.
The "devourers" of these organisms are called bacteriophages. To enter the host cell, they simply inject their own nucleic acid molecule through the membrane into the cytoplasm of the cell. Within half an hour, more than one hundred viral particles are formed in one bacterium.
How does a bacteriophage find its prey in nature? The fact is that for this the viral particle has special receptors that recognize the prokaryotic organism.
Ways for viruses to enter the body
Non-cellular life forms - viruses, having a primitive structure, are able to penetrate into the host organism in different ways. They depend on the features of its structure. For humans, the most common of these are the airborne route, penetration through the mucous membranes, food and water.
Carriers of such dangerous diseases as encephalitis and yellow fever are animals. In this case, ticks and mosquitoes, respectively. Through sexual intercourse, infection with hepatitis B and C, HIV and herpes is possible.
In nature, viruses that infect plants and fungi are also widespread. Penetration into these organisms occurs through sites of damage in the cell wall.
An important feature of viruses is their selectivity. This means that the particlesaffect humans, do not affect plant and bacterial organisms, and vice versa.
Viruses: benefit or harm
What benefit can these organisms bring if they cause the most dangerous deadly diseases: rabies, influenza, smallpox and others. The fact is that it is viruses - non-cellular life forms - that form immunity. This concept refers to the body's ability to resist infections. Immunity is innate, which is represented by blood antibodies, and acquired.
The latter is divided into natural and artificial. When transferring infectious diseases, the memory of viral particles remains in special blood cells - antibodies. When foreign organisms re-enter, they recognize the virus and destroy it by intracellular digestion - phagocytosis. Artificial immunity is acquired through vaccination. Its essence lies in the fact that the human body is infected with a weakened virus and antibodies begin to fight it, forming an immune memory.
Thanks to various forms of immunity, the body retains its vitality from the first breath of a baby throughout life. Every minute, a lot of viral particles enter the bloodstream. If the amount of antibodies is sufficient for their complete destruction, the person remains he althy. The disease occurs otherwise, when viral particles prevail and the resources of the immune system are not enough to neutralize them.
Non-cellular life forms - viruses and phages - are representatives of a separate kingdomwildlife, which is called Vira. In recent decades, the main task of epidemiologists is to create new vaccines against many dangerous viral diseases. The fact is that in the process of self-assembly, a mutation occurs and the formation of new viruses. This is especially true of HIV, which affects the immune system itself, completely making the body defenseless. This is a serious problem for modern science. We hope it will be resolved soon.
