Fig. 7. Arrhenius plots showing Na⁺/K⁺-ATPase maximal activity as a function of temperature (Kelvin) for (A) foot muscle and (B) hepatopancreas from O. lactea. Values are means ± s.e.m., N=4 independent preparations of enzyme. Assay mixtures were pre-incubated for 5 min in water baths set to specified temperatures prior to initiating reactions by the addition of Mg²⁺.ATP. Assays were conducted at maximal substrate concentrations. Arrhenius activation energy (E_A) was calculated from the linear part of the graphs.