[22] Membrane area and electrical capacitance

Publisher Summary This chapter describes electrical capacitance and the way it can be used to measure membrane surface area. To study exo- and endocytotic processes, it is necessary to have a parameter quantitatively related to its progress under different experimental conditions. Such information can be provided by a continuous measure of the membrane surface area as membrane is added or subtracted by the exo- or endocytotic process. Cell membrane elements such as channels, pumps, and exchangers may be directly studied through their electrophysiological effects on the membrane. Conversely, the equally important processes of exocytosis and endocytosis occur without producing clear electrical signals. The many ionic pathways of the membrane are protein molecules that reverse the membrane, and the proteins are thought to be held in a lipid matrix. The membrane can therefore be taken to be a sort of mosaic of insulating and conducting regions.