Flexi Says: The answer is actually “no.” A virus is essentially DNA or RNA surrounded by a coat of protein (Figure below). It is not made of a cell, and cannot maintain a stable internal environment (homeostasis). Recall that a cell is the basic unit of living organisms. So if a virus is not made of at least one cell, can it be living? Viruses also cannot reproduce on their own—they need to infect a host cell to reproduce. So a virus is very different from any of the organisms that fall into the three domains of life.