The entities that require a host cell because they are not able to make proteins on their own are viruses.

Here's why:

* Viruses lack the machinery for protein synthesis: Viruses are essentially genetic material (DNA or RNA) encased in a protein coat. They lack the ribosomes, enzymes, and other cellular components necessary to translate their genetic code into proteins.

* They rely on host cells: To replicate, viruses must infect a host cell and hijack its cellular machinery. They inject their genetic material into the host cell, which then uses its own resources to produce viral proteins, allowing the virus to assemble new viral particles.

Essentially, viruses are parasitic entities that depend entirely on host cells for their survival and reproduction.