Energy Requirement of Calcium Transport

As a consequence of the precipitation of calcium ions inside the vesicles, the product of the ion activities of calcium and the respective anions in the internal vesicular space is fixed by the solubility product of the precipitating salts (L). Since in the external solution changes of the ion activities of calcium (Ca0) and of the precipitating anions (A ) can be followed experimentally, the energy requirement for calcium uptake can be determined at every moment. The energy requirement is given by the expression  

Vj = rate of calcium influx Ve = rate of calcium efflux L = solubility product of calcium oxalate. 

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