Photosynthesis

The overall process of photosynthesis involves a number of interconnected processes. These processes, which are cyclic with respect to both energy and material, are related at some points to well-known respiratory processes. The carbon-reduction cycle in photosynthesis is now known in detail. All enzymes involved in this cycle have been isolated and the sources of energy required for its operation have been identified in terms of reducing agents and 'high-energy' phosphate. These sources of energy a r e derived ultimately from absorbed light energy which brings about the photolysis of water. Possible mechanisms for this photolysis and for the transfer of energy from the photolysis products to the carbon-reduction cycle are discussed here. Experimental data, in the form of quantum efficiency measurements, are presented and partially confirm the theories proposed for the mechanisms of energy transfer. A diagram of the complete process of photosynthesis containing the several cycles and their relations is presented