Noise in Biological Systems
Life: Avoiding or Exploiting Noise?
Institute for Chemistry and Biology of the Marine Environment
University of Oldenburg
A brief review of the diverse time and length scales of biology will be followed by a discussion of the various ways noise enters biological systems. The different sources of random fluctuations also motivate the useful distinction between internal and external noise. To set the stage for the session speakers I will explicitly consider the origin of noise in gene expression and neuronal systems. Appreciating the existence of noise will then lead to the question how fluctuations can be avoided or exploited to optimise or, at least, stabilise diverse biological functions. A common case where noise appears to be detrimental occurs in sensory perception. In such a situation a suppression or reduction of noise seems desirable. However, contrary to this standard view, using the threshold paradigm of stochastic resonance I will illustrate that omnipresent fluctuations can also be exploited to enhance perception. A second counter-intuitive mechanism is the conversion of undirected fluctuations into a directed net flux which firms under the titles of stochastic ratchet or Brownian motor. I will briefly indicate why and where this is relevant in biological systems. Both mechanisms, stochastic resonance and Brownian motors, belong to a class of noise-induced phenomena that illustrate a beneficial role of fluctuations in biological systems.
For further reading:
Rao C.V., Wolf, D.W. & Arkin, P. Control, exploitation and tolerance of intracellular noise. Nature (insight review article) 420, 231-237 (2003).
Hänggi, P. Stochastic resonance in biology: how noise can enhance detection of weak signals and help improve biological information processing. ChemPhysChem 3, 285-290 (2002).