Aqueous dispersions of PVP-protected Pd, Pt, Ph, Pd-Pt and Pd-Rh colloids (PVP=poly(2-vinylpyrrolidone)) were successfully applied for the catalytic hydrogenation of water soluble olefins and liposomes as models of biological membranes. The metal-PVP particles were anchored onto the surface of water insoluble, crosslinked poly(2-vinylpyrrolidone), PVPP. Both the sols and the supported catalysts are stable in time, non-permeable to the lipid membrane, and can be separated completely from the reaction mixture by decantation or centrifugation.