Dissimilation

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Dissimilation

 

in biology, the opposite of assimilation in the process of metabolism, consisting in the decomposition of organic compounds and conversion of protein, nucleic acids, fats, and carbohydrates (including those ingested) into simple substances. A number of dissimilation processes—respiration, fermentation, and glycolysis—play the central role in metabolism. As a result of these processes, energy contained in the molecules of complex organic compounds is released, partially to be transformed into adenosinephosphoric acids (chiefly ATP). The fundamental end products of dissimilation in all organisms are water, carbon dioxide, and ammonia. In animals these products are eliminated as they accumulate. In plant organisms CO2, partially, and NH3, totally, are used in the biosynthesis of organic matter, thus serving as the primary materials for assimilation.

The inseparable link between dissimilation and assimilation assures constant tissue renewal in organisms. Thus, in human blood one-half of the existing albumin is exchanged for new albumin molecules in ten days; the life span of erythrocytes is about four months. The relationship of the intensity of assimilation and dissimilation changes in relation to the stage of development, age, and physiological condition of the organism. The growth and development of the organism are characterized by the predominance of assimilation, which is manifested in the formation of new cells, tissues, and organs; their growth and differentiation; and in a general increase in body weight. In some pathological conditions and in starvation dissimilation usually predominates over assimilation, leading to a decrease in body weight.

S. E. SEVERIN and G. A. SOLOV’EVA


Dissimilation

 

in linguistics, one of the kinds of combinative sound changes in the course of speech. It occurs when one of two identical or similar speech sounds (adjacent or nonadjacent) changes to another distinct or less similar sound. Two examples of dissimilation are Latin peregrinum and Russian piligrim and Latinfebruaris and Russian fevral’.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In the model, [M.sub.Nrec] = mineralisation rate of recalcitrant organic-N to N[H.sub.4.sup.+]; [M.sub.Nlab] = mineralisation rate of labile organic-N to N[H.sub.4.sup.+]; Total [M.sub.n] = the sum of [M.sub.Nrec] and [M.sub.Nlab]; Ratio of [M.sub.Nlab] = the ratio of [M.sub.Nlab] to the sum of [M.sub.Nrec] and [M.sub.Nlab]; [O.sub.NH4] = gross rate of N[H.sub.4.sup.+] oxidation to N[O.sub.3.sup.-]; [O.sub.Nrel]; = the gross rate of recalcitrant organic-N oxidation to N[O.sub.3.sup.-]; and DNRA = the gross rate of dissimilatory NO, reduction to ammonium.
In addition, the process of dissimilatory nitrate or nitrite reduction to ammonium (DNRA) might present in strain Y-9.
pseudotuberculosis biovar Equi also shows the pathway of ammonification in dissimilatory nitrate reduction to ammonium, what has been proposed as catalyzed by the enzyme nitrate reductase Nar and nitrite reductase complex NrfAH, a membrane-associated cytochrome; see Figure 3.
Beard et al., "Fe, C, and O isotope compositions of banded iron formation carbonates demonstrate a major role for dissimilatory iron reduction in ~2.5Ga marine environments," Earth and Planetary Science Letters, vol.
They also isolated two new strains of dissimilatory Fe-reducing bacteria and supported the hypothesis that dissimilatory iron reduction is an important biogeochemical process in the environment [3].
These arrangements resulted due to the dissimilatory reductions that were subtly different in different microbes.
Dissimilatory sulfate reductase genes were highest (5-6%) in soils from filed 4F, 8F, and 10F.
Villemur, "Dissimilatory reduction of nitrate in seawater by a Methylophaga strain containing two highly divergent narG sequences," The International
In recent years, a wide range of electron donors have been demonstrated to chemically reduce [U.sup.6+] including reduced iron, including magnetite, [3] ferrous hydroxides, [4] [Fe.sup.2+] sorbed on hematite surfaces [5], and zero-valent iron [6]; microorganisms, including dissimilatory metal-reducing bacteria [7] and sulphate reducing bacteria [8]; organic compounds, including acetate [9] and lactate [10]; and dissolved and solid sulphide species [11-16].
The dissimilatory nitrate reduction to ammonium reaction occurs under much the same conditions as denitrification (Rivett et al.
Influence of dissimilatory metal reduction on fate of organic and metal contaminants in the subsurface.