What term refers to a parasitic particle that infects and resides in the cells of biological organisms?

The term that refers to a parasitic particle which infects and resides in the cells of biological organisms is a virus. Viruses are unique in their structure and functioning; they consist of genetic material (either DNA or RNA) encased in a protein coat and are unable to replicate on their own. Instead, they depend on a host cell's machinery to reproduce and propagate.

In contrast, bacteria are single-celled microorganisms that can live independently or as parasites but do not require a host cell for replication. Fungi, while they can also be parasitic in some cases, are generally more complex organisms that can survive independently. Protozoa are single-celled organisms that can be free-living or parasitic but, like bacteria, do not fit the definition of requiring a host cell for their infection process the way viruses do. Thus, the unique and specific nature of viruses makes this term the correct answer.