ABSTRACT
Fluctuations are natural features of biological networks given that molecules are discrete objects and, in many circumstances in biology, only present in small numbers. To be more specific, what we want to address here are some aspects of the functional role fluctuations can play in biological networks. We do this by way of example, since a general theory of fluctuations in biological systems does not yet exist.1 The examples are chosen as applications of two of the theoretical approaches discussed in the first part of the book, the Langevin-approach and the chemical master equation. The last part of this Chapter is devoted to a more general discussion of fluctuations, coming back to the distinction between intrinsic and extrinsic noise sources, this time in the context of biology.
