ABSTRACT
Photosynthesis, the most important biochemical process on the earth, is of such vital importance that no plant, animal, or human can live without it because they all depend on the energy, organic matter, and oxygen provided by it. Photosystem II (PSII) of the photosynthetic apparatus has been regarded as the engine of life [1]. However, considering both the cooperative relation between it and photosystem I (PSI) in photosynthesis and the key role of photosynthesis in the biosphere, we prefer to consider the two photosystems together, even the whole photosynthetic apparatus, which includes the carbon assimilation enzyme systems, as the engine of life driven by the energy from sunlight.
