Transportation energy requirements

Whereas sodium is predominantly extracellular, potassium is a major intracellular cation. An active energy requiring transport mechanism maintains this distribution and many diseases causing alteration of sodium levels also result in disturbances of potassium metabolism. 

H.M. Kalckar. 1991. 50 years of biological research From oxidative phosphorylation to energy requiring transport regulationRev. Biochem. 60 1-37. (PubMed)... 

Four classes of transmembrane proteins couple the energyreleasing hydrolysis of ATP with the energy-requiring transport of substances against their concentration gradient P-, V-, and F-class pumps and ABC proteins (see Figure 7-6). 

Both extracellular fluid (ECF) and intracellular fluid (ICF) contain electrolytes, a general term applied to bicarbonate and inorganic anions and cations. The electrolytes are unevenly distributed between compartments Na and Cl are the major electrolytes in the ECF (plasma and interstitial fluid), and and phosphates such as HP04 are the major electrolytes in cells (Table 4.1) This distribution is maintained principally by energy-requiring transporters that pump Na out of cells in exchange for (see Chapter 10). 

Although energy-requiring transport mechanisms ensure that valuable materials such as sugars and amino adds are actively absorbed into the bloodstream, useless and even harmful substances may pass across the intestinal barrier if their physicochemical characteristics are such as to allow them to traverse it by passive means. Once water and other materials have been absorbed they are distributed among the various fluid compartments. 

The choice of technology, the associated capital, and operating costs for a chlor—alkaU plant are strongly dependent on local factors. Especially important are local energy and transportation costs, as are environmental constraints. The primary difference ia operating costs between diaphragm, mercury, and membrane cell plants results from variations ia electricity requirements for the three processes (Table 25) so that local energy and steam costs are most important. 

Because most plastics may be fabricated in the melt and at quite low temperatures (e.g. 200°C) the energy requirements for processing are low. Since plastics generally have low densities, costs of transportation and general handling are also relatively low. 

Energy for maintenance is the energy required for survival, or non-growth related purposes. It includes activities such as active transport across membranes and turnover (replacement synthesis) of macromolecules. 

This means, of course, that an energy equation is necessary for the description of gas-liquid flows, along with the usual equations of movement and continuity. Transformation of the internal energy of dissolved gas into medium movement energy is what causes the observed pressure drop at the die entrance, e.g. the apparent decline in the amount of energy required to transport the gas-containing melt. 

Characteristically, the mechanisms formulated for azide decompositions involve [693,717] exciton formation and/or the participation of mobile electrons, positive holes and interstitial ions. Information concerning the energy requirements for the production, mobility and other relevant properties of these lattice imperfections can often be obtained from spectral data and electrical measurements. The interpretation of decomposition kinetics has often been profitably considered with reference to rates of photolysis. Accordingly, proposed reaction mechanisms have included consideration of trapping, transportation and interactions between possible energetic participants, and the steps involved can be characterized in greater detail than has been found possible in the decompositions of most other types of solids. 

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