Why are Biological Systems Nonlinear?

Abstract

Biological systems are nonlinear due to existence of weak interactions between its constituent parts. In this short review we deal with two very important biological systems, DNA molecule and microtubule. We show how different nonlinear terms in their Hamiltonians, together with different mathematical procedures, yield to different final results. In case of DNA, nonlinearity is modeled by Morse potential and the final result is nonlinear wave called breather moving along its chain. On the other hand, nonlinearity existing in microtubule is modeled by W-potential, which brings about kink soliton as the final result