Comprehensive Notes on Viruses

Size: Viruses are extremely small, measured in nanometers (nm). In contrast, bacteria are measured in micrometers (\mu m).
Mission: A virus's primary mission is to multiply itself.
Acellular Nature: Viruses are unique because they are acellular; they are not considered cells.
- They lack a cell membrane and cytoplasm.
- They are neither prokaryotic nor eukaryotic, meaning they do not belong to any biological domain or kingdom.
Nucleic Acid: A virus contains a single type of nucleic acid, either DNA or RNA. Some viruses can begin their life cycle with RNA.
Structural Components:
- Core: Contains the genetic material (DNA or RNA).
- Capsid: Surrounds the core; it is made of protein subunits called capsomeres. The capsid's function is to protect the viral DNA, much like a brick wall protects its contents.
- Envelope (Optional): An outer layer that some viruses possess. Viruses are classified as either non-enveloped (naked) or enveloped.
- Spikes (Optional): Present only in enveloped viruses, these structures anchor the virus to its envelope and are crucial for attachment to host cells.

Location of Multiplication: Viruses multiply exclusively inside living host cells, making them