Assimilation process

The further complicated way of CO2 assimilation to form CH20 flows through series of intermediate compounds and reactions (Calvin cycle). Let us show some results of calculations of total spatial-energy assimilation processes of CO2. When C02 is reduced to the level of its structural formation in CH20, the chemical bonds are reconstructed on all stages of the cycle. Therefore, the additional activation energy from ATP and NADPN is required. 

Nitrogen uptake that results in the formation of new biomolecules is termed an assimilation process, such as assimilatory nitrogen reduction. The processes that result in the release of DIN into seawater are referred to as dissimilations, such as dissimi-latory nitrogen reduction. An example of the latter is denitrification, in which nitrate and nitrite obtained from seawater serve as electron acceptors to enable the oxidation of organic matter. This causes the nitrate and nitrite to be transformed into reduced species, such as N2O and N2, which are released back into seawater. 

Morgan Z., Liang Y., and Hess P.C. (2006) An experimental study of anorthosite dissolution in lunar picritic magmas implications for crustal assimilation processes. Geochim. Cosmochim. Acta 70, 3477-3491. 

The combined activity of the rubisco oxygenase and the glycolate salvage pathway consumes 02 and produces C02—hence the name photorespiration. This pathway is perhaps better called the oxidative photosynthetic carbon cycle or C2 cycle, names that do not invite comparison with respiration in mitochondria. Unlike mitochondrial respiration, photorespiration does not conserve energy and may actually inhibit net biomass formation as much as 50%. This inefficiency has led to evolutionary adaptations in the carbon-assimilation processes, particularly in plants that have evolved in warm climates. 

In many plants that grow in the tropics (and in temperate-zone crop plants native to the tropics, such as maize, sugarcane, and sorghum) a mechanism has evolved to circumvent the problem of wasteful photorespiration. The step in which C02 is fixed into a three-carbon product, 3-phosphoglycerate, is preceded by several steps, one of which is temporary fixation of C02 into a four-carbon compound. Plants that use this process are referred to as C4 plants, and the assimilation process as C4 metabolism or the C4 pathway. Plants that use the carbon-assimilation method we have described thus far, in which the first step is reaction of C02 with ribulose 1,5-bisphosphate to form 3-phosphoglycerate, are called C3 plants. 

Nevertheless, bigger is not always better. In recent years, these largest companies have been very active as they vie with each other for market share, and a phenomenal growth in acquisitions and mergers has been observed. And it has to be said that, in the inevitable assimilation process, there has been some general concern in the overall marketplace with the quality of technical sales and services provided to end-user customers having suffered somewhat in the process. 

Some say that four or five small, nutritional meals a day are better than two or three larger ones— especially if one is a big meal at the end of the day. The reasoning is that the digestive and assimilation process works better with more frequent but smaller amounts. The smaller meals, however, should not be junk food. Instead, good snacks should include fresh fruit, raisins, raw carrots, celery sticks, and so forth. 

Some VOCs are toxic and carcinogenic. Two main sources of VOCs can be distinguished natural and anthropogenic. Natural sources are the vegetation processes of certain organisms, assimilation processes, forest fires, volcanic or geyser activity, and natural gas release (ca. 30-60 million tons per year). Anthropogenic... 

Photosynthesis and Respiration As we have seen, the addition or removal of CO2 has no effect on alkalinity. This would be tme for the photosynthesis process only if it were not accompanied by the assimilation of ions such ais NOJ, NH, and HPO. Since alkalinity is associated with charge balance, such assimilation processes must be accompanied by the uptake of H or OH (or release of OH or H ), that is, by alkalinity changes. Thus the photosynthetic assimilation of NH4 causes the uptake of OH or the release of H ions (Table 4.5). Similarly, alkalinity increases as a result of photosynthetic NOf assimilation conversely, the aerobic bacterial decomposition of biota to NO T is accompanied by a decrease in alkalinity. Such processes occurring in lard ecosystems are often not without influence on the pH and alkalinity of die adjoining aquatic ecosystems. 

We have seen that the assimilation in process II contributes negatively to the entropy change. Therefore, we expect that the reverse of the assimilation process, i.e., the deassimilation process, will increase the entropy. Figure H.2 shows a pure process of deassimilation where the entropy change is positive. 

A criticism of Brown s work has been given by Tswett, Zeitsch physik Chem, 76, 4x3, 1911, where the mechanism ol the assimilation process is tuitnei discussed... 

We may conclude this brief account of the carbon dioxide assimilation process by describing Baur s carbon dioxide assimilation model To appreciate this, however, it is necessary to say something first about photo-voltaic cells in general... 

Nitrate assimilation can occur in any plant organ in the presence of sufficient amounts of saccharides, which release during their oxidation the energy necessary for the reduction of nitrates. The entire reduction and assimilation process can be described by the following scheme ... 

Molecular mechanisms of nitrate accumulation depend not only on the nitrate reductase system, but also on the ability of roots to take from the soil, nitrate or ammonium ions, and on the plant s capacity for their conversion by assimilation processes to higher products. Besides this, the assimilation depends on the ability of a given genotype to transport substances necessary for the synthesis. It was shown that genotype differences of the nitrate reductase level do not depend on the nitrate content in tissues [25]. Nitrates are accumulated in plant organisms at high concentrations when aU the nitrogen accepted cannot be utilized for the production of amino acids and for subsequent protein synthesis [26]. This occurs when the plant, in the course of its metabolism, is unable to reduce the accepted nitrates into the assimilable ammonia form. 

Plant uptake is potentially an important assimilation process for removing organics from wetlands. Few studies have examined plant uptake of toxic organic contaminants. Accumulation of toxic chemicals in biota is usually quantified by a bioconcentration factor (BCF) ... 

Diffusion between the overlying water and the soil is an important assimilation process because it involves the transfer of toxic organics from a region of low density (the water column) to a region of high density (the sediment), where sorption can occur. Diffusion is particularly important in wetlands where long residence and low flow velocities are normal. 

Particles dropping out of the water column is a distinct process from burial of contaminants in the bed. Burial describes the removal rate of particle-bound toxic organics to deeper sediment layers from where they can no longer diffuse back into the water column. Burial is an important assimilation process for removing contaminants from biologically active zones. 

Sedimentation operates over a scale of months to years as opposed to other transport and assimilation processes. 

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