After collecting samples of the material found growing on last month's leftovers at the back of your fridge, you realize that you have discovered a new type of organism. You find that the cells have distinct microscopic subunits within them. Further, several of these subunits seem to be involved in the production and transfer of certain molecules. One molecule appears after a messenger molecule is sent from a subunit to another one. The first molecule then travels to another location, where it is covered in membrane and (eventually) released from the cell. What type of cells do you think these are?