Photosynthetic Production of Hydrogen from Water Although microorganisms are capable of carrying out different types of photosynthesis, that found in plants, algae, and cyanobacteria is best understood. Photosynthesis in these organisms is a complex series of reactions that use light energy to drive electron transfer from water to carbon dioxide to yield carbohydrates. Instead of using electrons harvested from water to synthesize carbohydrates from CO2, under certain conditions green algae and cyanobacteria can use them to reduce protons and produce hydrogen gas (H2). Molecular complexes involved in mediating electron flow from water to carbon-fixing or hydrogen-production reactions make up the photosynthetic electron-transport chain found in the thylakoid membranes of cyanobacteria and green algae. In eukaryotic green algae, thylakoid membranes are housed within a cellular organelle known as the chloroplast; in prokaryotic cyanobacteria, thylakoids are found in the cytoplasm as an intracellular membrane system (see Fig. A).
Credit or Source: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science. science.energy.gov/ber/
US DOE. 2005. Genomics:GTL Roadmap, DOE/SC-0090, U.S. Department of Energy Office of Science. (p. 210) (website)