A HeLa cell in telophase, a stage at which the chromosomes have separated
DR MATTHEW DANIELS/SCIENCE PHOTO LIBRARY
The field of thermodynamics, which deals with concepts like heat and entropy, provides valuable tools for assessing the equilibrium state of idealized systems of particles. However, when it comes to the intricate dynamics of living organisms, conventional thermodynamic laws may fall short. A recent series of experiments involving human cells aims to pave the way for a new framework that can better capture the complexities of biological systems.
Living organisms possess a unique property of being out of equilibrium, primarily due to the presence of molecules that actively consume energy within cells. Unlike inert systems, cells exhibit behaviors such as maintaining a set point, akin to an internal thermostat, to ensure their proper functioning. This dynamic behavior, governed by feedback mechanisms, presents a challenge for classical thermodynamics to fully explain.
Researchers N Narinder and Elisabeth Fischer-Friedrich from Dresden University of Technology embarked on a study using HeLa human cells, a widely used cancer cell line derived from Henrietta Lacks without her consent in the 1950s. By halting cell division and analyzing the membrane fluctuations of these cells using an atomic force microscope, the researchers delved into the differences in disequilibrium between living and non-living systems.
Interestingly, the study revealed that the traditional concept of “effective temperature” commonly used in non-living systems was not entirely accurate in capturing the fluctuations observed in living cells. Instead, the researchers proposed that “time reversal asymmetry” could be a more relevant quantity for quantifying the degree of disequilibrium in biological processes. This property explores how biological processes would vary if run in reverse, shedding light on the purpose-driven nature of these processes in living organisms.
Chase Broedersz from Vrije Universiteit Amsterdam commended the study for introducing novel tools to quantify non-equilibrium in biological systems. Yair Shokef from Tel Aviv University highlighted the significance of measuring multiple aspects of non-equilibrium simultaneously, emphasizing the need for a more comprehensive understanding of active biological systems through thermodynamics.
Looking ahead, Fischer-Friedrich expressed the team’s ambition to formulate a unique set of thermodynamic laws tailored specifically for living matter, considering its inherent set point and purpose-driven processes. The researchers are actively exploring physiological observables within cells as a starting point for deriving this fourth law of thermodynamics that could revolutionize our comprehension of life processes.
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