Carbon in living organisms

Carbon in living organic matter in the ocean surface layer. 

About 1,000 PgC in the oceans (out of the total of 3.8 X lO Pg) is organic carbon. Carbon in living organisms amounts to —3 Pg in the sea, in comparison to —550 Pg on land. The mass of animal life in the oceans is almost the same as on land, however, pointing to the very different trophic structures in the two environments. 

In any discussion of oi anic carbon in living organisms, it should be borne in mind that this pool represents roughly only 2% of the total organic matter in the sea and that this amount is far outweighed by dissolved organic matter (89%) and dead particulate organic matter (9%) (cf. Parsons, 1975). 

Porphyrins and chlorophylls are the most widespread natural pigments. They are associated with the energy-converting processes of respiration and photosynthesis in living organisms, and the synthesis of specific porphyrin derivatives is often motivated by the desire to perform similar processes in the test tube. The structurally and biosynthetically related corrins (e.g. vitamin B,j) catalyze alkylations and rearrangements of carbon skeletons via organocobalt intermediates. The biosyntheses of these chromophores are also of topical interest. 

The chemistry of living processes is complex, and many carbon-based molecules found in living organisms have extremely complicated stmctures. Because of this complexity, chemists have developed line structures, which are compact representations of the stmctural formulas of carbon compounds. Line structures are constructed according... 

Three processes that take place in living organisms - respiration in animals and plants, photosynthesis only in plants, and the precipitation of solids by some aquatic animals - have altered the primeval composition of the outer solid, liquid, and gaseous layers of the earth. Respiration consumes oxygen from the atmosphere and creates carbon dioxide. Photosynthesis, which does the opposite (consumes carbon dioxide and releases oxygen), has... 

As the one of the main end products of protein metabolism in living organisms, urea is a primary source of organic nitrogen in soil (from animal urine, fertilizers, etc.). Monitoring the level of urea is important for medicine, as well as for environmental protection. Urease is an enzyme that breaks the carbon-nitrogen bond of amides to form carbon dioxide, ammonia and water. This enzyme is widely used for determination of urea in... 

The reaction of peroxynitrite with the biologically ubiquitous C02 is of special interest due to the presence of both compounds in living organisms therefore, we may be confident that this process takes place under in vivo conditions. After the discovery of this reaction in 1995 by Lymar [136], the interaction of peroxynitrite with carbon dioxide and the reactions of the formed adduct nitrosoperoxocarboxylate ONOOCOO has been thoroughly studied. In 1996, Lymar et al. [137] have shown that this adduct is more reactive than peroxynitrite in the reaction with tyrosine, forming similar to peroxynitrite dityrosine and 3-nitrotyrosine. Experimental data were in quantitative agreement with free radical-mediated mechanism yielding tyrosyl and nitric dioxide radicals as intermediates and were inconsistent with electrophilic mechanism. The lifetime of ONOOCOO was estimated as <3 ms, and the rate constant of Reaction (42) k42 = 2 x 103 1 mol 1 s 1. 

Although the biocompatibility of carbon nanostructures has been explored in the past, deep knowledge of this subject should be increased since there are contradictory studies about the biological effects of these nanostructures in living organisms. The necessity of new protocols to evaluate the biocompatibility of CNTs has arisen since it seems that current protocols cannot be applied completely to carbon nanostructures. 

To make an IE the oxidizer must be combined with a suitable fuel. The majority of fuels available for use in IEs are hydrocarbons (materials containing mostly carbon and hydrogen). These materials are often referred to as organic compounds due to their prevalence in living organisms. Potential fuels can be broken down into three categories hydrocarbons, energetic hydrocarbons, and elementals. ... 

In the course of the carbon cycle, carbon moves from the atmosphere, where it mostly exists in the form of carbon dioxide, into biological molecules—the molecules that make up living things and the wastes and remains. The incorporation of atmospheric carbon into living organisms begins with the process of photosynthesis. Some atmospheric carbon dioxide is also removed from the atmosphere when it dissolves in the cold ocean waters at the north and south poles. 

All life on Earth is based on the element carbon. This means that in living organisms on Earth, body structures and the chemicals that take part in life processes are almost all carbon compounds. But scientists and science fiction enthusiasts alike have long speculated on the possibility that elsewhere in the universe there could be life forms based on other elements, particularly silicon. 

Carbon isotope fractionation effects of individual compounds were observed in living organisms and also as a result of enzymatic isotope effects and reaction kinetics in biological systems. Such fractionation effects have to be examined by isotope ratio mass spectrometry in order to understand specific processes in life sciences or in environment.75... 

In living organisms, chiral molecules are usually present in only one of their chiral forms. For example, the amino acids in proteins occur only as their l isomers glucose occurs only as its D isomer. (The conventions for naming stereoisomers of the amino acids are described in Chapter 3 those for sugars, in Chapter 7 the RS system, described above, is the most useful for some biomolecules.) In contrast, when a compound with an asymmetric carbon atom is chemically synthesized in the laboratory, the reaction usually pro-... 

All 20 of the common amino acids are a-amino acids. They have a carboxyl group and an amino group bonded to the same carbon atom (the a carbon) (Fig. 3-2). They differ from each other in their side chains, or R groups, which vary in structure, size, and electric charge, and which influence the solubility of the amino acids in water. In addition to these 20 amino acids there are many less common ones. Some are residues modified after a protein has been synthesized others are amino acids present in living organisms but not as constituents of proteins. The common amino acids of proteins have been assigned three-letter abbreviations and one-letter... 

Stanislao Cannizzaros main research interests were in the chemistry of carbon compounds found in living organisms. Cannizzaro did much to dispel the then widely held belief that the laws governing those chemicals were different from the laws governing chemicals not found in living organisms. 

It is of interest that two thermodynamically unstable forms of calcium carbonate, aragonite and vaterite. are found in living organisms as well as the more stable calcite. There appears to be no simple explanation for the distribution of the different forms in the various species. 

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