Models of Coupling and their Kinetic Characteristics
The arguments used in the controversy about the interaction between non-electrolyte and electrolyte transport are largely based on kinetic observations. Any transport system in which such interaction occurs, e. g. by cotransport, is likely to display special kinetic features which depend on the mechanism of coupling and on the concentrations of the activating ions in the adjacent solutions; they are usually interpreted in terms of preconceived models of hypothetical mechanisms. Most of these models are based on the hypothesis of a “ternary complex” formed between the transport carrier (X), the transported species (A), and the activating ion(s) (e. g. Na+). It should be kept in mind, however, that the formation of a ternary complex per se does not warrant the postulated transfer of energy, unless additional assumptions are made, such as, for instance, that the formation of the complex specifically modifies the carrier as to its affinities and/or mobility (1, 2).
KeywordsTernary Complex Conformational State Special Assumption Active Accumulation Transport Region
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