In this work we derive theoretical expressions for the FRAP measured o
n a liquid suspension of vacuoles labelled by a fluorescent probe boun
d to the surface membrane of these vacuoles. The bleaching laser beam
creates an inhomogeneity in the surface concentration of the probe mol
ecules. We consider the case in which the randomization of these probe
molecules on the vacuole surface occurs much faster than the fluoresc
ent recovery due to the vacuole diffusion. For a given value of the bl
eaching parameter K, we found that the bleaching fraction of the fluor
escent molecules and the fluorescence recovery rare are decreasing fun
ctions of the square ratio of the vacuole to the laser beam radius of
the FRAP instrument.