If you do an accounting of all the organ functions, and then ask if the cell has this function independently, nothing is left out... but only if you allow that intelligence arises from the cells.

So I believe intelligence arises from the cells and is an essential function of life, not only an emergent phenomena. The organs serve as division of labor amongst the cells in community for what they are already originally capable of themselves.

More musings in this direction https://sites.google.com/site/pablomayrgundter/mind