AJP - Regulatory, Integrative and Comparative Physiology, Vol 235, Issue 3 99-114, Copyright © 1978 by American Physiological Society
Proton semiconductors and energy transduction in biological systems
H. J. Morowitz
Energy transduction processes in biology are analyzed in terms of ordered
chains of hydrogen bonds. The theory is an extension of studies on proton
conductance in ice and is stimulated by current ideas on the role of
hydrogen ions in oxidative phosphorylation and photophosphorylation. The
possibility of a protochemistry paralleling electrochemistry is presented
along with experimental evidence. The theory relating transmembrane
electrochemical potential difference of hydrogen ion concentration to the
synthesis of ATP is reviewed. The thermodynamics of hydrogen transfer
across a membrane is treated including electrochemical and
electromechanical factors. As a prelude to considering ATP synthesis, the
acid-base dissociation reactions of ATP, ADP, and phosphate are analyzed.
The thermodynamics of ATP synthesis is discussed and a detailed model is
presented coupling the synthesis to proton transport. The model assumes a
gated proton semiconductor that carries protons and allows them to interact
specifically with well-defined substrate molecules. The physics of proton
transport is outlined and various methods examined in the context of
biological membranes. Emphasis is placed on solid-state proton
semiconductors and the present theory of such structures is given. A
section is included on possible biological applications of these
semiconductors.
