Living system, definition

Biochemistry can be defined as the science concerned with the chemical basis of life (Gk bios life ). The cell is the structural unit of living systems. Thus, biochemistry can also be described as the science concerned with the chemical constituents of living cells and with the reactions and processes they undergo. By this definition, biochemistry encompasses large areas of cell biology, of molecular biology, and of molecular genetics. 

Results from philosophical considerations on language show that attempts to define life lead to a dilemma, similar to that which occurred when trying to define water before molecular theory existed. Since no analogous theory of the nature of living systems exists, an infinite controversy as to the definition of life is unavoidable (Cleland and Chyba, 2002). 

One of the predicted effects of pollutants on eco stems suggested by Woodwell is a reduction in the standing crop of organic matter, which would lead to a reduction in nutrient elements held within the living system. The evidence discussed earlier definitely shows that primary production is much lower in an ozone>stressed conifer-forest ecosystem. This result would be anticipated in all similarly stressed natural ecosystems or agroecosystems. 

We have redefined "test facility", we have redefined "study". The next definition has to do with the living system that is undergoing the test. Up to now this has been traditionally rodents, dogs and primates. By using the term "test system" and defining "test system" as that to which the test substance is applied, we can now include soil, rodents, primates, bacteria and so on. I will not go into the specific proposed changes.in the text but you will see the emphasis in the text below which highlights the titles of certain sections ... 

Figure 13.4b emphasizes the finite nature and strong irreversibility of an economic system. The stock of energy and resources will eventually run out and so will the absorptive capacity of the environment for waste. An obvious extension of Figure 13.4b, therefore, is the one represented by Figure 13.4c. Just like in nature, waste has to be recycled. In nature, there is no real waste. Every form of waste is a resource for a living system. This living system is very small and called a microbe. Microbes make sure that all matter recycles in nature. Man needs to assume this humble but valuable and important role of microbes in the economic system and make sure that the material cycles get closed. Therefore, energy (or rather work) is required. But obviously this work should not be supplied from a nonrenewable source, like fossil fuels, but rather from a renewable source like the sun. Figure 13.4c therefore seems to be characteristic for a sustainable economic system and agrees remarkably with the definition of sustainability from biological systems A...

Given a NO/3NO- couple potential of 0.39 V, the effecter molecule of NOS would thus be expected to be ONOO, not NO. However, the direct detection of NO in living systems by a number of techniques (17,18,26) as well as the observation that activation of NOS results in antioxidant chemistry [briefly reviewed in (160-162)] suggest otherwise. The definitive mediation of vascular tone by NO (18, 31) and the discrete effects of HNO and NO donors observed in vitro, in vivo, and ex vivo corroborate the implications that NO cannot be readily reduced to NO- under physiological conditions (147). Additionally, the oxidation of methyl viologen by O2 was determined to be two orders of magnitude... 

Second, researchers can synthesize proteins without the use of living systems at all, employing only chemical techniques familiar to any chemist. A number of techniques have been developed for the chemical synthesis of proteins. Perhaps the simplest and most obvious (but definitely not the fastest) has been called stepwise synthesis. In this procedure, amino acids are added to each other, one at a... 

Observation of living systems shows them to be complex mixtures of different chemicals each of which functions to support one or more of the necessary tasks required to keep the organism alive . At one end of the spectrum of complexity lie the viruses and related simple proteins, such as prions, which cannot replicate by themselves but reproduce with the aid of other, higher, life forms. They therefore fulfill the definition of life to a very limited extent. At the other end of the spectrum there are the multicellular organisms such as humans with a vast diversity of processes that relate directly, and often more subtly, to the basic requirements of life. Even here, though, there is often a dependence on another living system. For example, humans cannot survive without vitamin Bi2 but are unable to synthesize it and must rely on external agents for its production. 

Until now, the compartmental model was considered as consisting of compartments associated with several anatomical locations in the living system. The general definition of the compartment allows us to associate in the same location a different chemical form of the original molecule administered in the process. In other words, the compartmental analysis can include not only diffusion phenomena but also chemical reaction kinetics. 

Implementation of the software design commences once the design is finalized. Sandpit (prototyping of application functionality) and development facilities are required to support system definition and development. A validation environment to perform qualification testing and a live environment completes the system development and operational architecture. 

Different biological questions can be addressed using different ON probe structures conveniently labeled with a selected F that exploits the main characteristics of fluorescence, which is the most sensitive spectroscopic technique (10). Their definitions are widely reported in companion articles and will not be discussed here. The applications can be divided into different series. One application concerns synthetic FONs that mimic the different structures found in living systems and aims at structural, dynamics, and interaction studies in vitro. Another... 

While the significance of radicals in biological systems has been appreciated for decades, there is relatively little definitive experimental infonnation on the identity of the radicals and even less on the mechanisms by which they affect the physiology of living systems. The paucity of detailed information is a direct consequence of the fact that most radicals are highly reactive and, therefore, short-lived transient species. Despite the tremendous advances in spectroscopic and laser photolysis techniques, much less is known about radicals than about closed-shell species. The treatment of radicals by theoretical methods is, however, only marginally more difficult than that of closed-shell molecules. It is for these reasons that the numerous applications of quantum chemical techniques to radicals have proven to be complementary to experimental studies. 

Organic—Substances associated with living systems is the old, but common definition. Now chemists apply it to most compounds that contain carbon atoms, especially rings or chains of carbon atoms. 

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