We present a statistical mechanical treatment relating the macroscopic adhe
sion energy of two surfaces, which can be obtained by micropipette aspirati
on studies, to the microscopic adhesion energy between individual bonds. Th
e treatment deals with the case of weak reversible bonds, so that the equil
ibrium partition function has significance. This description is coherent wi
th previous theories. Experiment and theory are compared to probe the natur
e of weak bonds in membranes, where local equilibria can be obtained. The c
ase of a bead and a vesicle decorated by nucleosides was considered.