Viruses themselves don't directly "provide energy" in the way that food does for animals. They are essentially parasitic and rely entirely on a host cell for their energy.

Here's how it works:

1. Virus Injects Genetic Material: A virus attaches to a host cell (like a bacteria, plant, or animal cell) and injects its genetic material (DNA or RNA) inside.

2. Host Cell Replicates Virus: The virus's genetic material takes over the host cell's machinery, forcing it to replicate viral components instead of its own.

3. Virus Assembles & Escapes: The replicated virus parts assemble into new viruses, which eventually burst out of the host cell, killing it in the process.

Therefore, the living thing that provides energy for a virus is the host cell. The host cell provides:

* ATP: The cell's energy currency.

* Enzymes and proteins: For viral replication and assembly.

* Building blocks: Like amino acids and nucleotides, to create new viral components.

In essence, the virus exploits the host cell's energy resources to replicate itself. This is why viruses are considered obligate intracellular parasites – they can only survive and replicate inside living cells.