Thermodynamic Aspects of Flagellar Activity

The frequencies of the beat of cilia and flagella from various organisms have been determined at temperatures in the range 5–35° C. Values of the activation enthalpy (ΔH‡, kcal./mole) and activation entropy (ΔS‡, e.u.) derived from the thermal dependence of frequency show a linear correlation of the form, ΔS‡ = 3·25 ΔH‡ – 50·75. The corresponding isokinetic activation free energy is 15·6 kcal./mole. The results support a hypothesis that the breakdown of an ATP-ATPase complex could be the common rate-limiting reaction for flagellar activity. Values of AH* and AS* for the decay of length or tension in striated muscles also fall on the same regression line but some smooth muscles show deviations.