There is no correlation between the type of the active site and the electron carrier
Good and efficient mediators should be permeable in a cell membrane and have higher electron affinity than the electron carriers
of the electron transport chains.
Most of the energy of fatty acids is extracted through oxidation to produce the reduced forms of high-energy electron carriers
nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide ([FADH.sub.2]).
This is a logical approach, given that natural photosynthesis involves excitation of electrons by light and so-called 'redox' reactions in which electrons are passed through a series of electron carriers
. In plants, a continuous flow of electrons from water to the compound NADPH is used to fix carbon, that is to lock the energy of sunlight into carbon bonds in glucose.
These efficient electron carriers
have served the same purpose in other alternative solar cells.