How does bacteriophage and HIV enter the host cell? What are their similarities and differences? What substances are involved in these processes?

The head of most phages contains DNA as a nucleic acid. At the end of the tail, tail threads (processes) are located, which contact the receptor sites on the surface of the bacterial cell and fix the bacteriophage. The tail basal plate contains an enzyme that destroys the bacterial cell wall, which ensures the penetration of virus DNA. Through the tail channel of the virus DNA is injected into the cell bacteria. It is embedded in bacterial DNA, inhibiting the print synthesis of bacterial proteins. Instead, DNA, RNA, and bacteriophage proteins are synthesized. In the bacterial cell, new bacteriophage particles are assembled, which leave the dead bacterium and are introduced into new ones.
HIV virions have a round shape and a diameter of 100-120 nm. The outer protein-lipid membrane, borrowed from the host cell, is penetrated by the virus’s own proteins. They play an important role in the process of penetration of the virus into the target cell. Under the membrane is a protein capsid forming an intermediate membrane. Under it, the core of the virus is a nucleoid, the protein shell of which has the shape of a truncated cone. Inside the nucleoid are two RNA molecules and the enzyme reverse transcriptase (revertase). This enzyme catalyzes the reverse transcription reaction in cells. The process of target cell damage proceeds as follows. On the surface of the cell there are specific receptor proteins with which the outer proteins of the virus are able to bind. Upon contact with the target cell, the virus protein is pulled out and the “tip” is released – another protein that can damage the cell membrane. The viral membrane fuses with the cell, and the contents of the virus enter the cell. After the virus penetrates with the help of the reverse transcriptase enzyme, one strand of viral DNA is first synthesized on the viral RNA matrix, and then the second strand is synthesized during replication. As a result of this process, viral DNA closes in the ring and integrates into the genome of the target cell. Transcription and translation processes begin on the viral DNA matrix, and viral RNA and proteins are synthesized. After completion of the synthesis processes, assembly takes place.

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