Focus

Photosynthesis is the biological process that converts sunlight into chemical energy. It provides the basis for life on Earth and is the ultimate source of all fossil fuels and of the oxygen we breathe. The primary light reactions occur with high quantum yield and drive free-energy-demanding chemical reactions with unsurpassed efficiency. Coupling of photosynthesis to hydrogenases allows some organisms to evolve H2. Research into understanding and applying the molecular details and reaction mechanisms of the involved catalysts is well under way.

Synopsis

Life needs free energy. On our planet this free energy is mostly provided by the Sun. The sunlight is captured and converted into chemical energy by a process known as photosynthesis (from Greek, photo, “light,” and synthesis, “putting together”). This process occurs in plants and many bacteria. The “big bang” of evolution was the development of oxygenic photosynthesis. In this process sunlight is employed to split the abundant water into the molecular oxygen we breathe. The protons and electrons gained are employed by the organism within complex reaction sequences to reduce CO2 to carbohydrates. The widespread availability of the electron source water allowed oxygenic organisms to spread and diversify rapidly. The O2 produced was initially toxic for most species, but those which learned to cope with the emerging oxygen-rich atmosphere were able to gain additional energy by “burning” organic matter.