Catabolic metabolism pathways

In summary, I have provided two examples of catabolic metabolic pathways linked to prodnction of ATP glycolysis, in which glucose is converted to lactate and pyrnvate and the citric acid cycle, in which acetate (derived from pyrnvate) is converted to carbon dioxide and water. In fact, these and other catabolic pathways generate more molecnles of ATP than 1 have so far let on. Now we need to do two things qnantitate the actnal yields of ATP and say something about how they are created. We begin by directing attention to the mitochondria. 

Catabolism Metabolic pathways that degrade molecules and complex compounds into smaller, simpler ones, releasing energy in the process. 

Metabolism Consists of Catabolism (Degradative Pathways) and Anabolism (Biosynthetic Pathways)... 

Interestingly, anabolism and catabolism occur simultaneously in the cell. The conflicting demands of concomitant catabolism and anabolism are managed by cells in two ways. First, the cell maintains tight and separate regulation of both catabolism and anabolism, so that metabolic needs are served in an immediate and orderly fashion. Second, competing metabolic pathways are often... 

Catabolism (Section 29.1) The group of metabolic pathways that break down larger molecules into smaller ones. 

Stimulation of all metabolic pathways, both anabolic and catabolic... 

The metabolism of microorganisms is complex. However, the metabolic pathways followed by anabolic and catabolic processes need to be described in simple terms to be applied for design and operation of urban wastewater systems. 

We should note at this point that the TCA cycle is more than just a means of producing NADH for oxidative phosphorylation. The pathway also provides a number of useful intermediates for other, often synthetic, pathways. For example, citrate is the starting substance for fat synthesis (Chapter 9) succinyl-CoA is required for haem production and 2-oxoglutarate and oxaloacetate in particular are involved with amino acid and pyrimidine metabolism. Pathways which have dual catabolic/anabolic functions are referred to as amphibolic . 

Wilson and Madsen [152] used the metabolic pathway for bacterial naphthalene oxidation as a guide for selecting l,2-dihydroxy-l,2-dihydronaphthalene as a unique transient intermediary metabolite whose presence in samples from a contaminated field site would indicate active in situ naphthalene biodegradation (Fig. 26). Naphthalene is a component of a variety of pollutant mixtures. It is the major constituent of coal tar [345], the pure compound was commonly used as a moth repellant and insecticide [345], and it is a predominant constituent of the fraction of crude oil used to produce diesel and jet fuels [346]. Prior studies at a coal tar-contaminated field site have focused upon contaminant transport [10,347], the presence of naphthalene catabolic genes [348, 349], and non-metabolite-based in situ contaminant biodegradation [343]. 

Dihydropyrimidine dehydrogenase is the first and the rate-limiting enzyme in the three-step metabolic pathway involved in the degradation of the pyrimidine bases uracil and thymine. In addition, this catabolic pathway is the only route for the synthesis of p-alanine in mammals. 

Anabolic metabolic pathways are the flip side of catabolic ones. Anabolic reactions are biosynthetic that is, they create complex molecules out of simpler ones. Anabolic pathways are reductive in nature and consume energy. In all these ways, anabolic pathways stand in contrast to catabolic ones. It is frequently the case that the end product of an anabolic pathway will inhibit the first enzyme in the same pathway. This makes a good deal of sense. Anabolic pathways require energy and if there is enough end product available there is little reason to keep making more of it. So an excess of the end product simply turns off the pathway by inhibiting the first enzyme ... 

The citric acid cycle is a catabolic, energy-generating metabolic pathway that is found enormously commonly in living nature. 

Jaworska, J.S., Dimitrov, S., Nikolova, N. and Mekenyan, O. (2002) Probabilistic assessment of biodegradability based on metabolic pathways CATABOL System. SAR OSAR Environ. Res., 13 (2),... 

FIGURE 4 Three types of nonlinear metabolic pathways (a) Converging, catabolic (b) diverging, anabolic and (c) cyclic, in which one of the starting materials (oxaloacetate in this case) is regenerated and reenters the pathway. Acetate, a key metabolic intermediate, is... 

FIGURE 23-13 Metabolic pathways for glucose 6-phosphate in the liver. Here and in Figures 23-14 and 23-15, anabolic pathways are shown leading upward, catabolic pathways leading downward, and distribution to other organs horizontally. The numbered processes in each figure are described in the text. 

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