The structure of viruses is non-cellular, since they do not have any organelles. In a word, this is a transitional stage between dead and living matter. Viruses were discovered by Russian biologist D.I. Ivanovsky in 1892 in the process of examining tobacco mosaic disease. The entire structure of viruses is RNA or DNA enclosed in a protein coat called a capsid. A virion is a formed infectious particle.
Influenza or herpes viruses have an additional lipoprotein membrane that emerges from the cytoplasmic membrane of the host cell. Viruses are divided into DNA-containing and RNA-containing, because they can have only 1 type of nucleic acid. However, the vast majority of viruses are RNA-containing. Their genomes are single-stranded and double-stranded. The internal structure of viruses allows them to multiply only in the cells of other organisms, and nothing else. They absolutely do not show any extracellular activity. The sizes of widespread viruses are from 20 to 300 nm in diameter.
The structure of bacteriophage viruses
Viruses that infect bacteria from the inside are called bacteriophages (phages). They are able to penetrate into the bacterial cell and destroy.
The body of the bacteriophage of Escherichia coli has a head from which a hollow shaft emerges, wrapped in a cover of contractile protein. At the end of this rod there is a basal plate on which 6 threads are fixed. Inside the head is a DNA molecule. Using special processes, the bacteriophage virus attaches to the body of E. coli bacteria. Using a special enzyme, the phage dissolves the cell wall and penetrates inside. Further, a DNA molecule is injected from the stem channel due to contractions of the head, and literally after 15 minutes the bacteriophage completely changes the metabolism of the bacterial cell to the desired way. The bacterium ceases to synthesize its DNA - it now synthesizes the nucleic acid of the virus. All this ends with the appearance of about 200-1000 phage individuals, and the bacterial cell is destroyed. All bacteriophages are divided into virulent and moderate. The latter do not replicate in the bacterial cell, and the virulent ones form a generation of individuals in the already infected area.
Viral diseases
The structure and vital activity of viruses is determined by the fact that they are able to exist only in the cells of other organisms. Having settled in any cell, the virus can cause serious illness. Often, agricultural plants and animals are attacked. These diseases sharply worsen the fertility of crops and are the cause of numerous animal deaths.
There are viruses that can cause various diseases in humans. Everyone knows diseases such as smallpox, herpes, influenza, polio, mumps, measles, jaundice and AIDS. All of them arise due to the activity of viruses. The structure of the smallpox virus is almost no different from the structure of the herpes virus, since they are included in the same group - Herpes Virus, which includes some other types of viruses. Nowadays, human immunodeficiency virus (HIV) is actively spreading. How to overcome it, while no one knows.