Viruses are non-cellular forms of life. Life forms: non-cellular and cellular

All organisms are composed of cells - the smallest structural-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 own worthy niche among the kingdoms of living nature? Let's find out more.

Viruses - non-cellular forms of life

In translation from the Greek language the name of these organisms is translated as "poison". And this is not accidental. No one has ever seen them with the naked eye, but almost everyone has suffered their influence. After all, flu symptoms in winter are knocking at home without demand.

It is now known that viruses are a non-cellular form of life. The biology of these organisms remained a mystery for many centuries. And it was only at the end of the 19th century that the Russian physiologist Dmitry Iosifovich Ivanovskii proved that the viruses are the causative agents of many diseases. The scientist examined the tobacco plant, which was affected by tobacco mosaic. He noticed that if the juice of a sick plant penetrates into a healthy one, then its defeat will occur.

The structure of viruses

Why are viruses - non-cellular forms of life? The answer is simple: their body does not consist of cells. It is a nucleic acid molecule surrounded by a protein coat - a capsid. There are DNA and RNA-containing viruses.

Depending on the characteristics of the structure, non-cellular forms of life - 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 serves as an additional protective shell.

Why are they alive?

So, viruses are non-cellular forms of life, they do not have the usual membrane and organelles - permanent cellular structures that perform certain functions. By what attributes do they refer to living organisms? They are capable of the process of reproduction. And, being outside the host organism, they show no sign of existence. Once the virus is in the cell, it begins to synthesize its proteins. At the same time, the process of suppressing the product of protein'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 proper synthesis processes stop. As a result, the body becomes ill, since the virus and the energy of the host cells need energy to begin the process of reproduction .

Bacteriophages

Viruses are non-cellular forms of life that can parasitize in any organism. And unicellular prokaryotic bacteria are no exception.

"Devourers" of these organisms are called bacteriophages. For penetration into the host cell, they simply inject their own nucleic acid molecule through the membrane into the cytoplasm of the cell. Within half an hour, one bacterium forms more than one hundred virus particles.

How does a bacteriophage find its prey in nature? The fact is that for this virus particle has special receptors, which recognize the prokaryotic organism.

Ways of getting viruses into the body

Non-cellular forms of life - viruses, having a primitive structure, are able to penetrate the host organism in various ways. They depend on the characteristics of its structure. For humans, the most common of these are the airborne path, penetration through mucous membranes, food and water.

Carriers of such dangerous diseases as encephalitis and yellow fever are animals. In this case, ticks and mosquitoes, respectively. At sexual contacts infection with hepatitis B and C, HIV and herpes is possible.

In nature, viruses that attack 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 particles that affect a person do not affect plant and bacterial organisms and vice versa.

Viruses: Benefit or Harm

What benefits can these organisms bring if they cause dangerous deadly diseases: rabies, flu, smallpox and others. The fact is that it is viruses - non-cellular forms of life - that form the immune system. This concept means the body's ability to resist infections. Immunity is congenital, which is represented by antibodies of blood, and acquired.

The latter is divided into natural and artificial. When transferring infectious diseases, the memory of virus particles remains in special blood cells - antibodies. When they re-enter foreign organisms, they recognize the virus and destroy it by intracellular digestion - phagocytosis. Artificial immunity is acquired as a result of vaccination. Its essence lies in the fact that the human body is infected with a weakened virus and antibodies begin to fight it, forming a immune memory.

Thanks to various forms of immunity, the body retains its vitality since the first breath of an infant throughout life. Every minute, many virus particles enter the bloodstream. If the number of antibodies is sufficient for their complete destruction, the person remains healthy. The disease occurs otherwise, when the viral particles predominate and the immune system resources are not enough to neutralize them.

Non-cellular forms of life - viruses and phages - are representatives of a separate realm of living nature, called Vira. In recent decades, the main task of epidemiologists is the creation of new vaccines against many dangerous viral diseases. The matter is that in the process of self-assembly a mutation and the formation of new viruses occur. 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 that it will be solved in the near future.