Biogenic isoprene emission as expression of dissipativity, a fundamental cell property

Abstract

Energy dynamics of isoprene biosynthesis and the mechanism of isoprene emission are discussed in view of their fundamental role in dissipativity of living cells. The significance of basic principles of colloidal chemistry for biological energy conversion is emphasized. The idea is put forward of the existence in living cells of the universal energy-dynamic structural unit, termed “biological micelle,” that accounts for the transport and distribution of protons over the cell volume. This unit is responsible for the creation and maintenance of physiological pH at any metabolically active site within the cell. Particular attention is paid to the involvement of F-type ATPase in the active proton transport from the thylakoid interior to the F1 domain of ATP-synthase and to recycling of protons from the outer cell surface to the thylakoid lumen due to H+-pumping activity of the thylakoid ATPase. The mechanism responsible for the outflow of entropy deS through the production of isoprene by protonation of dimethylallyl pyrophosphate (DMAPP) has been found. The stable steady-state condition of any thermodynamic system, including the living system, is correlated with the maximum entropy production. The rate of isoprene emission increases with temperature, which compensates for the decrease in outflow of thermal entropy deS. When the ambient temperature is increased, the sum of deS removed as heat and deS removed with isoprene emission remains constant. Thus, photobiosynthesis of isoprene is a special case of the entropy deS dissipation that provides a stable stationary state to the cell.