(4dv) Energy Conversion in Biological Molecular Machines
In order to carry out numerous biological functions, various molecular machines are at work within a cell. These molecular machines are responsible for conversion of energy, stored in Adenosine triphosphate (ATP), into various other forms of energy such as electrochemical potential across the cell membrane, work required for active transportation and etc. Although the basic duties of molecular machines are not very different form their macroscopic counterparts, these machines function in a totally different environment where electrostatic and solvent interactions replace the forces of gravity and inertia. More importantly, due to their small size, molecular machines are persistently affected by significant thermal fluctuations. Here we propose a theory that explains how various molecular machines take advantage of the thermal fluctuation to perform their tasks via a biased Brownian ratcheting mechanism. Our theory explains how the tight coupling of the ATP reaction to the molecular machines production cycle would lead to high energy efficiency.