  The hopping model for cargo transport by molecular motors introduced in Refs.
goldman1, goldman2, is extended here in order to incorporate the movement of
cargo-motor complexes. In this context, hopping process expresses the
possibility for cargo to be exchanged between neighbor motors at a microtubule
where the transport takes place. Jamming of motors is essential for cargos to
execute long-range movement in this way. Results from computer simulations
performed using the extended model indicate that cargo may execute
bidirectional movement in the presence of motors of a single polarity,
confirming previous analytical results. Moreover, these results suggest the
existence of a balance between cargo hopping and the movement of the complex
that may control the efficiency of cargo transfer and cargo delivering.
Considerations about the energy involved in the transport process show that the
model presented here offers a considerable advantage over other models in the
literature for which cargo movement is restricted to the movement of
cargo-motor complexes.
