Book excerpt: Equations of Membrane Biophysics provides an introduction to the relevant principles of thermodynamics, kinetics, electricity, surface chemistry, electrochemistry, and other mathematical theorems so that the quantitative aspects of membrane phenomena in model and biological systems could be described. The book begins by introducing several phenomena that arise across membranes, both artificial and biological, when different driving forces act across them. This is followed by separate chapters on thermodynamic principles related to properties of dilute aqueous electrolyte solutions along with a review of the principles of electrostatics, electrochemical principles, Fick's laws of diffusion, and the rate theory of diffusion; the quantitative aspects of the electrochemistry of solutions and membranes, and the quantitative relations between charges and electrostatic potentials related to surfaces and interfaces; and membrane theories pertaining to electrical potentials arising across a variety of membranes. Subsequent chapters deal with steady-state thermodynamic approaches to several transport phenomena in membranes; tissue impedance, cable theory, and Hodgkin-Huxley equations; and fluctuation analysis of the electrical properties of the membrane.