Concepts and techniques in plant membrane physiology

The vast majority of known biological transport processes carry electrical charge associated with the transported solute(s) and therefore affect the voltage across membranes. Other membrane-related activities, such as the exo- and endocytotic traffic of vesicles, also influence the electrical capacitance and, at least transiently therefore, the voltage across membranes. Indeed, (trans)membrane voltage or ‘membrane potential’ is the simplest of parameters to record across biological membranes. It is also one of the most commonly cited, although its significance is frequently misunderstood. Accounting for membrane voltage is essential, but is only part of any quantitative description of transport that moves charge across membranes.