Metabolism purposes

To this point, the pathway has generated a pool of pentose phosphates. The AG° for each of the last two reactions is small, and the three pentose-5-phosphates coexist at equilibrium. The pathway has also produced two molecules of N/ DPH for each glucose-6-P converted to pentose-5-phosphate. The next three steps rearrange the five-carbon skeletons of the pentoses to produce three-, four-, six-, and seven-carbon units, which can be used for various metabolic purposes. Why should the cell do this Very often, the cellular need for... 

Molecular Oxygen, a Toxic By-Product of Some Photosynthetic Processes, Can Be Utilized for Metabolic Purposes... 

The NADH glut also inhibits fatty acid oxidation. The metabolic purpose of fatty acid oxidation is to generate NADH for ATP generation by oxidative phosphorylation, but an alcohol consumer s NADH needs are met by ethanol metabolism. 

The overabundance of NADH also inhibits fatty acid oxidation. The metabolic purpose of fatty acid oxidation Is to generate NADH for ATP generation by oxidative phosphorylation, but an alcohol consumer s NADH needs are met by ethanol metabolism. In fact, the excess NADH signals that conditions are right for fatty acid synthesis. Hence, triacylglyc-erols accumulate in the liver, leading to a condition known as Tatty liver."... 

Compare the entry-level substrates, products, and metabolic purposes of glycolysis and gluconeogenesis. 

Recall What is the metabolic purpose of lactic acid production ... 

Another important issue is that of the proper control variables. We have just alluded to the possibility of viewing microbial response as a resource allocation problem. The resources might, for example, constitute only a critical resource such as ATP that is the primary source of energy for metabolic purposes. It is difficult to be any more specific about this issue at this inceptive stage of our work. 

The activity of majority of enzymes is regulated by the concentration of their own substrates in a MichaeUs-Menten fashion. However, such a control may be insufficient for some metabolic purposes. For example, in order to increase the velocity of a simple Michaelian enzyme from o.iV to 0.9V, it is necessary to increase the substrate concentration from Xm/9 to that is, an 81-fold increase. Similarly, an 81-fold increase in inhibitor concentration is required to reduce the velocity from 90% to 10% of the uninhibited value. On one hand, the concentration of metabolites in vivo vary within relatively narrow limits wltile, on the other hand, the activity of specific enzymes must be increased or decreased within very large limits. Consequently, in addition to a simple Michaelian kinetics, nature has a need for additional control mechanisms for the regulation of enzyme activity in vivo. 

All media contain a carbon source for the generation of cellular metabolic energy. Glucose is the most common carbon source due to its capability of being rapidly converted into energy. Alternate carbon sources, such as fructose, mannose, galactose or pyruvate and glycogenic amino acids, may be used by cultured cells for various metabolic purposes. 

For many of the metabolic purposes, trace elements are needed. Cobalt aids in the transfer of methyl groups from/to organic or inorganic molecules. (Vitamin B12, cobalamin, is involved in the methylation of heavy metals such as mercury.) Iron, as Fe or Fe, is required for the electron transport system, where it acts as an oxidizable/reducible central atom in cytochromes of nonheme iron-sulfur proteins. Magnesium acts in... 

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