Figure 2 Permeability of organelle membranes to H+ is directly correlated to steady state pH of the organelle. PH+ for the organelles was calculated using the model [3] from time course of effects of bafilomycin on organelle pH assuming cytosolic pH remained constant. Data taken from: our work on Golgi in CFT1 [1] (oval shows range of data) and HeLa [2] cells, recycling endosomes in Cos cells [14], secretory granules in AtT-20 cells (Wu M and Machen T, unpublished) and TGN in CHO cells (Giorgi G and Machen T, unpublished); other data were taken from papers describing steady state pH and effects of bafilomycin as shown: JL [16], JHK [19], and ND [18].