Photosynthesis origin

Studies (see, e.g., (101)) indicate that photosynthesis originated after the development of respiratory electron transfer pathways (99, 143). The photosynthetic reaction center, in this scenario, would have been created in order to enhance the efficiency of the already existing electron transport chains, that is, by adding a light-driven cycle around the cytochrome be complex. The Rieske protein as the key subunit in cytochrome be complexes would in this picture have contributed the first iron-sulfur center involved in photosynthetic mechanisms (since on the basis of the present data, it seems likely to us that the first photosynthetic RC resembled RCII, i.e., was devoid of iron—sulfur clusters). 

McKay, C. P. and Hartman, H. Hydrogen peroxide and the evolution of oxygenic photosynthesis. Origins of Life and Evolution of the Biosphere 21 157-163 1991. 

Oxygen oeeurs in the atmosphere in vast quantities as the free element O2 (and O3, p. 607) and there are also suhstantial amounts dissolved in the oeeans and surfaee waters of the world. Virtually all of this oxygen is of hiologieal origin having been generated by green-plant photosynthesis from water (and earbon dioxide).The net reaetion ean be represented by ... 

About 8(1 percent of the electric energy used in the United States is derived from stored energy in coal. The stored energy has its origin in photosynthesis. Coal is the end product of the accumulation of plant matter in an oxygen-deficient environment where burning is thwarted. Formation takes millions of years. Proven reseiwes of coal in the United States are upwards of 500 billion tons, a reserve so great that even if coal continues to be burned at a rate of over one billion tons per year, the reserves will last for hundreds of years. 

Fischer projections and, 977-978 glycosides and, 989-990 l- 4 links in, 997-998 origin of name. 973 photosynthesis of, 973-974 see also Aldose, Monosaccharide vaccines from, 1004-1005 Carbon, ground-state electron configuration of, 6... 

Hartman, H. (1998). Photosynthesis and the origin of life. Origins Life Evol. Biosphere, 28, 515-521... 

Fig. 6.5 Microbial iron and sulfur cycles that may have dominated biogeochemical cycling before the origin of oxygenic photosynthesis, aerobic respiration and possibly before the use of oxides of nitrogen.

Long-term aim of our project is the construction of a biomolecular device for hydrogen production in combination with light-driven water-splitting as it occurs in the natural process of photosynthesis in plants. Such a semiartificial device should combine the best suited components found in various native systems which - up to now - cannot be found in an individual native system due to incompatibilities and/or different origin (pro- and eukaryotic, meso- and thermophilic, aerobic - anaerobic environment). Advantage of such a system is... 

Aliphatic hydrocarbons, a diverse suite of compounds, are an important lipid fraction which is either natural (i. e., from photosynthesis by marine biota inhabiting the surface waters or by terrestrial vascular plants) or anthropogenic (i. e., of petroleum origin from land runoff, and/or industrial inputs). Aliphatic hydrocarbons have been studied and characterized from various environmental multimedia [1,53-56,99-109]. 

Combustion. An exothermic chemical reaction involving oxidation of an organic compound and results in the creation of H2O and CO2. The heat results from rupture of the chemical bonds. In the case of organic materials such as wood, the original energy was stored by photosynthesis. 

A potentially more serious problem than that of low efficiency is the requirement that the photochemical absorber operate without any significant side reactions. For example, if the quantum yield for side reactions were 1%, then after only 100 cycles the concentration of the absorber would have decreased to 37% of its original concentration. It is interesting that in photosynthesis each chlorophyll molecule processes at least 10 photons in its lifetime in a leaf. This means that the quantum yield for reactions leading to the degradation of chlorophyll must be less than 10-5 ... 

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