Photosynthesis: nature's energy supply
Photosynthesis is the only natural system on the planet that harvests solar energy. All life on earth derives it energy from it, either directly (plants) or indirectly (animals and man). The system has evolved over billions of years and is essentially unchanged during the last few billion years. From this I dare to say that photosynthesis must be the most efficient system to indeed harvest solar energy.
During my PhD study (1973 to 1978) I investigated the secondary reactions in one of the two photosystems (Photosystem 2) of photosynthesis in green plants and algae. Photosystem 2 reduces water to oxygen, while the electrons are transported accross a membrane to reduce plastoquinone (PQ). Using spectroscopic methods in near ultraviolet, visible and infrered and electron spin resonance techniques, I tried to identify the molecules and chemical reactions between them in the membranes.
I have contributed to the identification of charge accumulating complexes at both the donor and acceptor side of Photosystem 2 (PS II in the above graphic). The paper I enjoyed the most was the one that described for the first time absorbance changes in the near ultraviolet that showed a periodicity of four and in a series of flashes following a dark adaptation period. These were interpreted as caused by respectively the oxygen evolving complex at the donor side, later identified as a manganese containing molecule and a quinone at the acceptor side of PS II (MPJ Pulles, HJ Van Gorkom, JG Willemsen (1976) Absorbance changes due to the charge-accumulating species in System 2 of photosynthesis, Biochimica et Biophysica Acta (BBA) - Bioenergetics Volume 449, Issue 3, Pages 536-540).
Can photosynthesis solve the climate and energy issues?
Photosynthesis has evolved over more than three billion years and has remained the same over the last one billion years. From this, one might conclude that, despite this long period of evolution, nature was not able to find a more efficient system to harvest solar energy and convert it into the main energy carrier, used by all life on earth: food.
,,to be continued >>