Organisms autotrophic

Autotroph Organism which uses carbon dioxide as the sole carbon source. Autotrophic nitrification Oxidation of ammonium to nitrate through the combined... 

As we began this chapter, we saw that photosynthesis traditionally is equated with the process of COg fixation, that is, the net synthesis of carbohydrate from COg. Indeed, the capacity to perform net accumulation of carbohydrate from COg distinguishes the phototrophic (and autotrophic) organisms from het-erotrophs. Although animals possess enzymes capable of linking COg to organic acceptors, they cannot achieve a net accumulation of organic material by these reactions. For example, fatty acid biosynthesis is primed by covalent attachment of COg to acetyl-CoA to form malonyl-CoA (Chapter 25). Nevertheless, this fixed COg is liberated in the very next reaction, so no net COg incorporation occurs. 

Primary production maintains the main carbon flux from the atmosphere to the biota. In the process of photosynthesis, CO2 from the atmosphere is reduced by autotrophic organisms to a wide range of organic substances. The complex biochemistry involved can be represented by the formula... 

Kurt, M., Dunn, I. J. and Bourne, J. R. (1987) Biological denitrification of drinking water using autotrophic organisms with H2 in a fluidized- bed biofilm reactor. Biotechnol. Bioeng. 29, 493-501. 

Autotrophs Organisms that can use inorganic substances as their energy source. 

How organisms induce oxide formation depends upon the degree to which iron participates in their physiological processes. Organisms which precipitate iron oxides extracellularly are either autotrophic or heterotrophic. Autotrophic organisms obtain energy for metabolism by oxidation of Fe . This biotic oxidation reaction is... 

Flow characterization methods, reactive intermediates, 46 156-164 Fluorescence, 19 68, 46 156 emission spectrum, Holobacfer, 36 420, 422 microscopy, autotrophic organisms, 36 118-119... 

Outline the pathway for biosynthesis of L-leucine from glucose and NH4+ in autotrophic organisms. In addition, outline the pathways for degradation of leucine to C02, water, and NH4+ in the human body. For this overall pathway or "metabolic loop," mark the locations (one or more) at which each of the following processes occurs. 

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... 

Cysteine is formed in plants and in bacteria from sulfide and serine after the latter has been acetylated by transfer of an acetyl group from acetyl-CoA (Fig. 24-25, step f). This standard PLP-dependent (3 replacement (Chapter 14) is catalyzed by cysteine synthase (O-acetylserine sulfhydrase).446 447 A similar enzyme is used by some cells to introduce sulfide ion directly into homocysteine, via either O-succinyl homoserine or O-acetyl homoserine (Fig. 24-13). In E. coli cysteine can be converted to methionine, as outlined in Eq. lb-22 and as indicated on the right side of Fig. 24-13 by the green arrows. In animals the converse process, the conversion of methionine to cysteine (gray arrows in Fig. 24-13, also Fig. 24-16), is important. Animals are unable to incorporate sulfide directly into cysteine, and this amino acid must be either provided in the diet or formed from dietary methionine. The latter process is limited, and cysteine is an essential dietary constituent for infants. The formation of cysteine from methionine occurs via the same transsulfuration pathway as in methionine synthesis in autotrophic organisms. However, the latter use cystathionine y-synthase and P-lyase while cysteine synthesis in animals uses cystathionine P-synthase and y-lyase. 

Aromatic compounds arise in several ways. The major mute utilized by autotrophic organisms for synthesis of the aromatic amino acids, quinones, and tocopherols is the shikimate pathway. As outlined here, it starts with the glycolysis intermediate phosphoenolpyruvate (PEP) and erythrose 4-phosphate, a metabolite from the pentose phosphate pathway. Phenylalanine, tyrosine, and tryptophan are not only used for protein synthesis but are converted into a broad range of hormones, chromophores, alkaloids, and structural materials. In plants phenylalanine is deaminated to cinnamate which yields hundreds of secondary products. In another pathway ribose 5-phosphate is converted to pyrimidine and purine nucleotides and also to flavins, folates, molybdopterin, and many other pterin derivatives. 

This cycle represents the quantitatively most important C02 fixation pathway in Nature. It is found in most aerobic autotrophic organisms, ranging from diverse photosynthetic and chemolithoautotrophic bacteria to chloroplasts of eukaryotic algae and higher plants [5]. It is centered around carbohydrates, with ribulose 1,5-bisphosphate being the C02 acceptor (Figure 3.1). 

Where primary production is the sole source of organic matter for heterotrophic N formation, the maximum ratio of heterotrophic organic N (HON) formation to autotrophic organic N (AON) formation can be calculated from autotrophic production (AP), microbial heterotrophic production (MHP), and the C N ratios of autotrophs (C Naut) and microbial heterotrophs (C N ), such that... 

Autotrophic organisms (plants and algae) which synthesize organic matter from inorganic materials (e.g., algae photosynthesize sugars from C02). Volume 2(1). 

McCollom TM (1999) Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa. J Geophys Res 104 30,729-30,742... 

Assimilation of DON involves the uptake and incorporation of organic forms of N, such as amino acids, into biomass by both heterotrophic and autotrophic organisms. 

Autotrophs organisms (e.g., vascular plants and algae) that make their own food for energy. 

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