Transfer across membranes effect site

Cholanic acid also possesses the ability of transporting cations across a lipophilic membrane but the selectivity is not observed because it contains no recognition sites for specific cations. In the basic region, monensin forms a lipophilic complex with Na+, which is the counter ion of the carboxylate, by taking a pseudo-cyclic structure based on the effective coordination of the polyether moiety. The lipophilic complex taken up in the liquid membrane is transferred to the active region by diffusion. In the acidic region, the sodium cation is released by the neutralization reaction. The cycle is completed by the reverse transport of the free carboxylic ionophore. 

The answer is c. (Murray, pp 123-148. Scriver, pp 2367-2424. Sack, pp 159-175. Wilson, pp 287-317.) The electron transport chain shown contains three proton pumps linked by two mobile electron carriers. At each of these three sites (NADH-Q reductase, cytochrome reductase, and cytochrome oxidase) the transfer of electrons down the chain powers the pumping of protons across the inner mitochondrial membrane. The blockage of electron transfers by specific point inhibitors leads to a buildup of highly reduced carriers behind the block because of the inability to transfer electrons across the block. In the scheme shown, rotenone blocks step A, antimycin A blocks step B, and carbon monoxide (as well as cyanide and azide) blocks step E. Therefore a carbon monoxide inhibition leads to a highly reduced state of all of the carriers of the chain. Puromycin and chloramphenicol are inhibitors of protein synthesis and have no direct effect upon the electron transport chain. 

The more Upid-soluble agents are well absorbed after oral administration, have ubiquitous effects at both peripheral and central cholinergic sites, and may be sequestered in lipids for long periods of time. Lipid-soluble organophosphorus agents also are well absorbed through the skin, and the volatile agents are transferred readily across the alveolar membrane. 

When a membrane doped with anionic sites is in contact with an aqueous solution of rX , 1+ is exchanged across the interface (Figure 7.1 A). The aqueous counter ion is excluded from the membrane phase because of the conunon ion effect Transfer of an aqueous counter ion into the membrane phase must be followed by simultaneous transfer of the analyte so that the electroneulrality is maintained in the two phases. The salt-extraction process can be defined as... 

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