Life processes are manifesting properly only by correlated and multiple biomolecular interactions taking permanently place in all the cells. The sine qua non molecular interactions for life processes are the specific interactions, that is, those conducting to preferential associations between partners. These interactions are the result of many synergic factors. The common specific interactions are the enzyme-substrate and the protein-ligand interactions. In the case of enzymes, the natural ligands are the specific substrates bound to enzyme active sites before they are split into products. Quantitatively, the specific interactions are characterized by the association (affinity) constant, a high affinity meaning a great value for this constant. The specific interactions are also ubicuitary both at supramolecular and cellular levels facilitating a coherent interplay of all the living matter components. Indeed, a large variety of subtle biological phenomena taking place at cellular level, are involving cell-to-cell interactions, more specifically, membrane-to-membrane interactions of the apposing cells. The cell-to-cell interactions are mainly determined by the composition and spatial structure of their membrane and their membrane peripheries (i.e. glycocalyx) and also by the particular composition of the liquid micro-environment. Some specific interactions both at molecular (first part) and cellular (second part) level are presented and commented.