How do single-celled predators chase other cells?

Question

From my understanding, single celled organisms have been seen avoiding, and chasing, potential food or other organisms.How do they accomplish this? They do not have eyes or ears or a nervous system. My understanding is that chemical reactions are involved somehow.How do single-celled predators chase other cells? What happens on a chemical level?**Edit**:*To help keep a more constrained question, the single-celled organism I am considering is [Paramecium](https://microbewiki.kenyon.edu/index.php/Paramecium)*

Answer 1

You are right that they do not have eyes or ears, however they have signalling pathways that allow them to track food sources.

On the surface of single-celled organisms are a number of receptor proteins. A decent comparison for these are taste buds. They allow the cell to sample the local region for known markers that inform it that there is something to eat in this area. It could be a waste product the food source excretes, proteins it sheds or some chemical used for quorum sensing. These all are basically "dinner bell" signals that tell the paramecia that it should change it's direction of motility towards the source and essentially hones in on the bacteria following concentration gradients.

If you are interested in learning more please let me know!

Dr. CJ

It would be like closing your eyes and following the smell of freshly baked cookies to their source.

Answer 2

Via cell communication. Very much like bacterial quorum sensing. Organisms have receptors that "sense" other organisms' ligands or chemicals they release. The organisms then move toward the highest concentration of the ligand.