Final answer:
Outside of living cells, viruses are metabolically inert as they do not engage in any metabolic activities. They need to infect host cells to replicate, using the host's cellular machinery. Thus, outside of living cells, viruses do not grow or undertake metabolism.
Step-by-step explanation:
The question of what viruses do outside of living cells can be answered by understanding their fundamental nature and how they operate within host cells. Outside of living cells, viruses are metabolically inert, meaning they do not carry out any of the metabolic processes that living organisms do. They do not have the necessary cellular machinery, including ribosomes, ATP, cytoplasm, or a plasma membrane, required for metabolism or replication.
Instead, viruses are essentially packages of genetic material wrapped in a protective protein coat, known as a capsid, and require a host cell to undertake any activity that could be considered living-like. Within a host cell, viruses hijack the cell's machinery to replicate themselves, using the host's ribosomes and enzymes. This reliance on a host cell to replicate is why viruses are often referred to as obligate intracellular parasites.