ABSTRACT
The dioxygen species of the biosphere worked as an electron acceptor in biosystems for the generation of biochemical energy and also as the substrate for developing oxidase and oxygenase enzyme systems in the biosynthesis of a variety of cell components and organelles. In this respect, the response of dioxygen concentration in the atmosphere plays a significant role in the evolution of microbes, plants, and animals of the biosphere and in their signaling, regulatory, and control mechanisms. The appearance of oxygen in the atmosphere, its metabolism in later developed aerobic living beings, and subsequent evolutionary changes in pathways and concepts have brought the living biosphere to the modem oxygenase era through early mechanistic observations and propositions. All biocells of prokaryotic, eukaryotic, and archaebacterial domain of biosphere are exposed to oxygen of atmosphere through this cycle.
