Red cells aren't they cells? The basis of any organism are cells. All that is not a cell, can not "think", and therefore eat. But chemical reactions and interactions are possible.
The main role in the life of the body are cells. All the reactions that occur outside the cells are not important and sometimes even harmful, for example, all kinds of bacteria or fungi can live there. All that is located between the cells is carrying and transport and therefore should not alter or disturb the original product. Target cell