A three component, liposome-bound photochemical molecular device (PMD) consisting of energy and electron transfer reactions is described. Bilayer membrane surface-associated dyes, 5,10,15,20-tetrakis[4-(trimethylammonio)-phenyl]-21H,23H-porphine tetra-p-tosylate salt and N,N’-bis[(3-trimethylammonio)propyl]thiadicarbocyanine, tribromide, are the energy donor and acceptor, respectively, in a blue light stimulated energy transfer reaction along the vesicle surface. The electronically excited cyanine is quenched by electron transfer from the phospholipid membrane bound triphenylbenzyl berate anion, which is located in the lipid bilayer interior. The PMD exhibits sequential reactions following electronic excitation with the novel feature that the steps proceed with orthogonal orientation : energy transfer occurs parallel to the membrane surface, and electron transfer occurs perpendicular to the surface. Photobleaching and fluorescence quenching experiments verify the transfer reactions, and Stern-Volmer analysis was used to estimate the reaction rate constants. At the highest concentrations examined of energy and electron acceptor ca. 60% of the photoexcited porphyrins were quenched by energy transfer to the cyanine. The use of liposomes of well defined composition and dimensions in conjunction with molecular components that associate with the bilayer in a predictable manner permit the accurate estimation of molecular binding volumes and local concentrations for the analysis.