## Abstract

There are two famous equations in membrane biophysics that we must understand; one is for the average current from a population of opening and closing channels, the other is for fluctuations, or noise, around the average current. If we have a population of
where

*N*channels (the total number without considering status, i.e., whether or not they are open or closed). The*N*is therefore a constant for all practical purposes, and we do not consider that channels may enter or leave the membrane; we only require*N*channels to be available to be opened. The average current is$$I = Nip$$

*i*is the current through an open channel and*p*is the probability that the channel is open. The probability that the channel is open or the probability of a channel being open is not equivalent to the probability of*opening*(see Fig. 2.20 and Fig. 2.21). In the following sections, we explore a common formula for*p*:$$p = \frac{1}
{{1 + e^{ - {\text{a}}(V - {\text{b}})} }}$$

## Keywords

Boltzmann Equation Nuclear Envelope Channel Density Loaded Transporter Charged Macromolecule
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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## Copyright information

© Springer Science+Business Media New York 1997