Proteinoid microspheres are stable hollow spheres of diameter of the o
rder of 5 mu m. Their stability is discussed in terms of macroscopic e
nergies. It is shown that bulk and surface energy contributions alone
cannot lead to stable microspheres. If electrostatic energy, due to tr
ansmembrane voltage, is taken into account, stable hollow spheres are
proved to exist. For several reasons, however, this result should not
be regarded as the ultimate explanation of microsphere stability.