This work reports the development of a physico-chemical model for liga
nd-receptor interactions. It considers receptors having groups of diff
erent binding sites in equilibrium and far from equilibrium where each
of these may have multiple occupancies. The obtained results under ap
propriate simplifications give the well known Scatchard, Hill and Adai
r relations and provide a very interesting tool for studying receptor-
ligand phenomena and for determining the related parameters and intera
ction energies.