The circulatory system transports substances between the exchange surface and cells. It delivers oxygen and glucose to the tissues for respiration, which is the release of energy to cells.

Why do virtually all cells ... how respiration works. We know far less about why it works that way. Mitchell worked on mitochondria because he could; they are a tractable experimental model.

Microbial fuel cells generate an electric current by ... because it provides an environment that is favourable for respiration. The model by Kato Marcus et al. focuses on the biofilm anode ...