Photosynthesis hydrogen transport

In the biological reactions associated with metabolism systems of electron and hydrogen transport are associated with both respiration and photosynthesis. The electron transport or respiratory chains, involved with the oxidation of organic and inorganic substances by the micro-organisms include a series of components each of which can exist in two forms, i.e. oxidised or reduced forms. Each component of the system is characterised by a constant redox potential. 

Fig. 1. Abbreviated Z-scheme for the light reactions of oxygenic photosynthesis showing electron transport pathways to carbon fixation and hydrogen production.

Give an estimate of how much land (or water surface) area should be set aside for allowing world-wide needs for hydrogen as a transportation fuel to be derived by microbial photosynthesis. How much arable land would be used if the same amount of hydrogen were to be produced by fermentation. Discuss the possibility for combining the land (or ocean/waterway) use with other uses. 

A special electrochemical cell was often employed to detect the photosynthetic activity of immobilized thylakoids. " " With this electrochemical micro-cell, it was possible to detect a photocurrent of free or immobilized thylakoid membranes in the absence of exogenous artificial electron acceptor. The photosynthetic origin of the photocurrent was demonstrated by an inhibition in the presence of the photosynthetic inhibitor diuron. The inhibition of the photocurrent by catalase, an enzyme that degrades hydrogen peroxide, demonstrated that dissolved oxygen was involved. " The ability of oxygen to act as an electron acceptor for the photosynthesis membrane was initially demonstrated by Mehler. This process, known as pseudocyclic electron transport or Mehler... 

Fig. 2 A biomimetic system for solar-energy conversion. A molecular triad embedded in the bilayer membrane allows photoexcited electrons to be transported across the membrane to acceptor species in the interior. This charge transport is accompanied by the transmembrane flow of hydrogen ions, leading to a decrease in pH inside the compartment. This proton-motive force is then used to drive ATP synthesis by the membrane protein ATP synthase, as it is in photosynthesis.

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