Antenna entropy in plant photosystems does not reduce the free energy for primary charge separation

•The antenna entropy does not reduce the free energy available for charge separation.•Photosystem antenna entropy is the configurational entropy of a canonical ensemble.•The excitation energy of a photosynthetic antenna doesn't undergo energy dilution.

We have investigated the concept of the so-called “antenna entropy” of higher plant photosystems. Several interesting points emerge:1.In the case of a photosystem which harbours an excited state, the “antenna entropy” is equivalent to the configurational (mixing) entropy of a thermodynamic canonical ensemble. The energy associated with this parameter has been calculated for a hypothetical isoenergetic photosystem, photosystem I and photosystem II, and comes out in the range of 3.5 - 8% of the photon energy considering 680 nm.2.The “antenna entropy” seems to be a rather unique thermodynamic phenomenon, in as much as it does not modify the free energy available for primary photochemistry, as has been previously suggested.3.It is underlined that this configurational (mixing) entropy, unlike heat dispersal in a thermal system, does not involve energy dilution. This points out an important difference between thermal and electronic energy dispersal.

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