Viruses

It is a non-cellular form of life, inert outside cells and acquiring living characteristics only inside cells. They do not have their own protein synthesis and can only multiply during the host cell’s protein synthesis. They contain only one type of nucleic acid DNA or RNA. Metabolic processes do not occur in them, and they exhibit absolute parasitism inside the cell. After the virus enters the cell, rapid synthesis of the virus’s DNA or RNA and proteins occurs, using the host cell’s enzymes and substrates as well as sources of energy. At the same time, in virus-infected cells, all synthesis of the host cell’s nucleic acids and proteins stops. Reproduction of virus particles continues until the cell’s death.

Viruses are about 100-1000 times smaller than the cells they infect. The smallest viruses have a diameter of about 20 nm. The largest viruses have a diameter of about 300 nm.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė