Introduction to Virus

Viruses are submicroscopic infectious agents with a nucleic acid core, either DNA or RNA, encased in a protective protein shell called a capsid.

They are obligate intracellular parasites, relying entirely on host cells for replication and assembly of new viral particles.

Some viruses have lipid envelopes derived from the host cell’s plasma membrane. These envelopes incorporate viral proteins.

Enveloped viruses use surface proteins or glycoproteins to attach to host cells, while non-enveloped viruses rely on capsid proteins to bind to specific receptors.

Once attached, viruses deliver their genetic material into the host cell.

For instance, HIV carries an RNA genome and employs reverse transcriptase to convert its RNA into DNA, which integrates into the host genome.

Conversely, herpesviruses contain DNA genomes.

Some viruses, like bacteriophages, possess complex structures with capsids, tail sheaths, and tail fibers, enabling them to inject genetic material directly into bacterial cells.

Viruses infect plants, animals, and bacteria disrupting cellular processes and causing damage or cell lysis.