The Boltzmann factor, DNA melting, and Brownian ratchets: Topics in an introductory physics sequence for biology and premedical students

TL;DR

This paper introduces three biologically-relevant biased random walk models—DNA melting, helicase activity, and actin polymerization—to illustrate key physical concepts like the Boltzmann factor and Brownian ratchets for biology students.

Contribution

It presents accessible models linking physics principles to biological processes, enhancing interdisciplinary understanding for premedical students.

Findings

DNA melting modeled via Boltzmann factor

Helicase activity as Brownian ratchet example

Force-velocity relationship in actin polymerization

Abstract

Three, interrelated biologically-relevant examples of biased random walks are presented: (1) A model for DNA melting, modelled as DNA unzipping, which provides a way to illustrate the role of the Boltzmann factor in a venue well-known to biology and pre-medical students; (2) the activity of helicase motor proteins in unzipping double-stranded DNA, for example, at the replication fork, which is an example of a Brownian ratchet; (3) force generation by actin polymerization, which is another Brownian ratchet, and for which the force and actin-concentration dependence of the velocity of actin polymerization is determined.