Motor Proteins and the 2nd Law of Thermodynamics

Abstract

Motor proteins doing intracellular transport or rotation consume chemical fuels (ATP) to make directional motion in an isothermal environment. From a general physical perspective, any directional motion in an isothermal environment costs a finite amount of energy, even though no work is done. Otherwise the 2nd law of thermodynamics would be violated. Hence the 2nd law requires a finite energy price for ‘pure’ direction of a motor protein. But what is the least possible price, quantitatively speaking? And how close to this least price are motor proteins? In this talk, I shall show that a universal equality captures the 2nd-law decreed price of direction, and matches experimental observation of motor proteins like kinesin-1 and F1-ATPase. These results offer quantitative evidence that the two motor proteins function near the physical boundary set by the 2nd law. [