Before revision:  We prove optimality in terms of mean first passage times for three different, frequently encountered intracellular transport tasks: i) the narrow escapeproblem (e.g. transport of cargo to a synapse or other specific region of the cell membrane, ii) reaction kinetics enhancement (e.g. binding of a mobile particle with a immobile or mobile target within the cell, iii) the reaction-escape problem (e. g. release of cargo at a synapse after intracellular vesicle pairing.
After revision:  We prove optimality in terms of mean first passage times for several standard search problems - narrow escape, reaction partner finding, reaction-escape problem (e. g. release of cargo at a synapse after intracellular vesicle pairing.