Assimilation constituents

The Fermentation Process The process by which this antifungal substance is produced is an aerobic fermentation of an aquaous nutrient medium inoculated with a pimaricin-producing strain of Streptomycesgihrosporeus. The nutrient medium contains an assimilable source of carbon such as starch, molasses, or glycerol, an assimilable source of nitrogen such as corn steep liquor and Inorganic cations such as potassium, sodium or calcium, and anions such as sulfate, phosphate or chloride. Trace elements such as boron, molybdenum or copper are supplied as needed in the form of impurities by the other constituents of the medium. 

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

Especially in dicotyledonous plant species such as tomato, chickpea, and white lupin (82,111), with a high cation/anion uptake ratio, PEPC-mediated biosynthesis of carboxylates may also be linked to excessive net uptake of cations due to inhibition of uptake and assimilation of nitrate under P-deficient conditions (Fig. 5) (17,111,115). Excess uptake of cations is balanced by enhanced net re-lea,se of protons (82,111,116), provided by increased bio.synthesis of organic acids via PEPC as a constituent of the intracellular pH-stat mechanism (117). In these plants, P deficiency-mediated proton extrusion leads to rhizosphere acidification, which can contribute to the. solubilization of acid soluble Ca phosphates in calcareous soils (Fig. 5) (34,118,119). In some species (e.g., chickpea, white lupin, oil-seed rape, buckwheat), the enhanced net release of protons is associated with increased exudation of carboxylates, whereas in tomato, carboxylate exudation was negligible despite intense proton extrusion (82,120). 

Cell molecule synthesis (anabolism), i.e., formally, reduction of the precursor to the level of a hypothetical average cell molecule CaHpOY N6 and assimilation of nitrogen (e.g., NH3), representing synthesis of all cell constituents ... 

Since in mammalian species metals first need to be assimilated from dietary sources in the intestinal tract and subsequently transported to the cells of the different organs of the body through the bloodstream, we will restrict ourselves in this section to the transport of metal ions across the enterocytes of the upper part of the small intestine (essentially the duodenum), where essentially all of the uptake of dietary constituents, whether they be metal ions, carbohydrates, fats, amino acids, vitamins, etc., takes place. We will then briefly review the mechanisms by which metal ions are transported across the plasma membrane of mammalian cells and enter the cytoplasm, as we did for bacteria, fungi and plants. The specific molecules involved in extracellular metal ion transport in the circulation will be dealt with in Chapter 8. 

Only 1.2% of the carbon of 2,4-D added to stream water was converted to organic particulate matter, the solids fraction in water containing the microbial cells. This lack of significant carbon assimilation may be a result of the inability of the microorganisms to obtain carbon and energy for biosynthetic purposes at these low concentrations, the immediate use of the carbon for respiration in order for the cells to maintain their viability (i. e., for maintenance energy), or the rapid decomposition and mineralization of the cells and their constituents. 

Although wood is a perishable material, this can be seen as an advantage, in that wood can be disposed of into the environment at the end of its useful life, where its molecular constituents are broken down by natural processes and assimilated into nutrient cycles. 

Over the past several decades there have been increasingly strong demands in Europe and the United States that atmospheric chemistry research be directly useful in developing scientific risk assessments and public policies. For example, one component of the EUROTRAC program (European Experiment on Transport and Transformation of Environmentally Relevant Trace Constituents in the Troposphere) ...is expected to assimilate the scientific results from EUROTRAC and present them in a condensed form, together with recommendations where appropriate, so that they are suitable for use by those responsible for environmental planning and management in Europe (EUROTRAC, 1993). 

In the foregoing remarks it is seen, that the conditions necessary for the production of the organic constituents of plants are moisture, aud the presence everywhere of bodies to furnish carrion and nitrogen. The essential food of plants must net be one which is Found in one place, and is absent from another. Wherever water is, there most be found these sources of carbon and nitrogen. No substances fulfil these conditions but Carbonic acid and ammonia. Hence the whole theory of the nourishment of a plant, so for as the formation of ita organic portions is concerned, consists in the constant supply of carbonic acid and ammonia, and as a substitute for the latter, nitric acid, from which carbon and nitrogen are assimilated. 

In the first instance, the roots of planta may take up all substances in solution without selection. But this action is not one of simple imbibition as in the case of sponges. Liebig-, in a recent memoir, maintains that the spongioles, in obtaining their supply of saline matter, exert a real decomposing action on certain Ill-defined compounds, which the saline mattar forms with the. insoluble constituents of the soil, Those substances which are conveyed to planta in solution are retained in greater or less quantity, or are entirely rejected when not fit For assimilation. 

Cysteine not only is an essential constituent of proteins but also lies on the major route of incorporation of inorganic sulfur into organic compounds.443 Autotrophic organisms carry out the stepwise reduction of sulfate to sulfite and sulfide (H2S). These reduced sulfur compounds are the ones that are incorporated into organic substances. Animals make use of the organic sulfur compounds formed by the autotrophs and have an active oxidative metabolism by which the compounds can be decomposed and the sulfur reoxidized to sulfate. Several aspects of cysteine metabolism are summarized in Fig. 24-25. Some of the chemistry of inorganic sulfur metabolism has been discussed in earlier chapters. Sulfate is reduced to H2S by sulfate-reducing bacteria (Chapter 18). The initial step in assimilative sulfate reduction, used by... 

Animal organisms generally require effective assistance of intestinal flora, as in ruminants, to assimilate inorganic nitrogen into body protein. This accounts for the human needs of a daily requirement of 70-80 grams of protein, However, over half of the protein-constituent amino adds can be derived from other amino acids by their own enzymic reactions. Thus, amino acids are classified as essential or nonessential. Amino acid requirements vary with the physiological state of the animal, age. and possibly with the nature of the intestinal flora. 

The latter is technically much more difficult than the former. The use of assimilation techniques to maximise the information retrieved from tropospheric sounding is foreseen as essential. A number of experiments have been or will be developed which are designed to determine the concentration of constituents in the troposphere. 

J.M. Felts, H. Itakura and R.T. Crane, The mechanism of assimilation of constituents of chylomicrons, very low density lipoproteins and remnants - a new theory, Biochem. Biophys. Res. Commun. 66 (1975) 1467-1475. 

HS interact with nutrient assimilation of both macro- and micro-elements, by enhancing the nutrient use efficiency. This capacity is related to both (a) HS chelating properties and (b) an interaction with plasma membrane enzymatic constituents. 

Almost all physiological processes in plants take place in the presence of water. Essential anabolic reactions (photosynthesis, assimilation, and protein synthesis), and catabolic ones (respiration and hydrolysis) occur in an aqueous cellular environment. Essential elements absorbed by plant roots, and the foods and other metabolites manufactured by the leaves and other tissues, move in aqueous solution from the regions of absorption or manufacture to other parts of the plant where additional anabolic reactions and ultimate food storage take place. Water is the major constituent of protoplasm, and is particularly abundant in young and growing tissues. 

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