The cell of an organism upon which a virus depends is called a host cell.

Here's why:

* Viruses are obligate intracellular parasites: This means they cannot reproduce or function on their own. They require a host cell to provide them with the necessary resources and machinery for replication.

* Viruses hijack host cell machinery: Once inside a host cell, a virus uses the cell's ribosomes, enzymes, and other components to produce more viral particles.

So, the host cell is essentially a temporary "factory" for the virus, allowing it to multiply and spread.