Biology as Poetry: Bioenergetics

Bacteriophage Ecology Group

Z Scheme

Representation of noncyclic electron flow in photosynthesis in terms of energy associated with electrons, rising abruptly, gradually falling, then rising abruptly again.

The first rise it due to boosting of electron energy to an excited state in association with photosystem II. This followed by a gradual decline as mediated by an electron transfer chain. Finally, the electron's energy is again boosted in association with photosystem I.

The pathway, graphing electron-associated energy against time, takes on a shape reminiscent of a Z turned on its side (90 degrees rotation, counter clockwise). All of this occurs within the context of the light reaction of photosynthesis and associated photophosphorylation. See by contrast cyclic electron flow.

The Z shape of the Z scheme technically is that seen following a redox diagram. In addition, if the entirety of noncyclic electron flow is followed then the Z is followed by part of a subsequent Z, that is, a zigzag.

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