How do viruses differ from prokaryotic and eukaryotic cells?

Viruses are fundamentally different from both prokaryotic and eukaryotic cells in that they are not classified as living organisms; they lack cellular structures that define those life forms. Unlike prokaryotic cells, which are single-celled organisms that can exist independently and carry out metabolic processes, and eukaryotic cells, which are more complex and contain organelles, viruses do not possess the necessary machinery for metabolism or energy production. Instead, viruses are composed of genetic material (either DNA or RNA) surrounded by a protein coat and, in some cases, a lipid envelope.

Viruses require a host cell to replicate; they invade the cellular machinery of a host organism to reproduce and assemble new viral particles. This reliance on host cells for replication underscores their distinct nature compared to living cells, as they cannot reproduce independently. Thus, the statement that viruses are not considered prokaryotic or eukaryotic and lack metabolism accurately captures their unique characteristics within the biological classification.