If I understand right, lower cells in that bio-cable, “eat” sulfides and used the released electrons from sulfides to obtain energy. After then, they transfer that “used” electrons to upper side to bind them with oxygen. So, the electrons are not accumulated at lower parts.

My question is that How the upper cells obtain energy? They just transfer the electrons that coming from bottom to oxygen to finish respiration cycle. They are just making the “garbage” process of respiration. Is energy is maintained by bottom part?

Thanks.