Photosynthesis

Abstract

With the establishment of conditions for optimum culturing and measurement, there is now final proof that in photosynthesis at high as well as low light intensities the light energy can be almost completely converted into chemical energy. There is thus drawn to a close an investigation that was initiated many years ago in Berlin in the Imperial Institute of Physics (9). The second result is the establishment of a general physical mechanism of photosynthesis, involving an interplay between light energy and respiratory energy, and therewith the solution of the quantum problem in photosynthesis. The third result is the establishment of the function of chlorophyll as a stoichiometric, chemically reacting component in photosynthesis. There remains the special chemistry of photosynthesis. In this still-unfinished field of investigation, the latest discovery is the labile carbon dioxide of Chlorella, connected with the decomposition and resynthesis of glutamic acid in living Chlorella, and connected with the possible function of the amino acids, aspartic and glutamic, in the binding and reduction of carbonic acid. The dissociating CO₂ is bound by Chlorella only in the presence of O₂ and of cellular glutamic acid. This CO₂ is released if the oxygen pressure is lowered below 2 mm of water or if—in the presence of oxygen—the glutamic acid is split in the living Chlorella, for example, by N/10,000 benzoquinone. This is the CO₂ that is used in light and taken up in the dark (8).