1.2 Virus vs. Cell: Key Differences

To understand viruses, it is helpful to compare them with cells:

• Cells are living systems. They have a cell membrane, cytoplasm, and internal structures (organelles in eukaryotic cells). Cells can produce energy and reproduce on their own.
• Viruses are not complete living systems. They do not have cytoplasm, organelles, or metabolism. Outside a host cell, a virus is inactive.

This difference explains why viruses are often described as being on the border between living and non-living: they show life-like behavior only inside a host cell.