Physicist Jeremy England, with whom I’ve exchanged views in the past about the origin of life, has a new book out, Every Life Is on Fire: How Thermodynamics Explains the Origin of Living Things. I just finished reading the book, and I must compliment England on writing one of the most insightful works on the subject that I have ever encountered. He explains in accessible terms the thermodynamic challenges to life’s genesis, and he offers profound insights into how cells continuously maintain their integrity against the constant onslaught of thermal fluctuations degrading their structure. I believe his book should be required reading for anyone wishing to gain a deeper understanding of the physical principles constraining life’s origin.
England begins by describing how his book interweaves the discussion of the science of life with his Orthodox Jewish faith. Each chapter begins with a passage from either the book of Genesis or Exodus that he connects to the chapter’s main theme. He then introduces the field of thermodynamics, which comprises the bedrock for his theory of life. Next, he identifies several key characteristics defining life:
- Its comprising different parts interlocking in coordinated relationships.
- Its ability to harvest and consume matter and energy from its surroundings to serve as fuel for its activities.
- Its skill at self-repairing to maintain a coherent structure with a defined pattern.
- Its capacity to sense, predict, and react deliberately to the world around it.
- Its power to reproduce.
The Need for Engines
England then focuses on the thermodynamic principles that form the core of his argument. His discussion closely parallels my own writings on the topic (here, here). He begins by describing how natural processes drive systems toward states of higher entropy (higher probability if all states were equally probable), lower energy, or both. He then explains how entropy (S) and energy (E) in a system at a given temperature (T) are often combined into the free energy measure (F): F = E – TS. Natural processes, without external assistance, always tend toward lower free energy. In contrast, life represents a state of very low entropy and very high energy (i.e., high free energy).
England then illustrates how the only way for a system (e.g., a chemical mixture) to overcome the thermodynamic forces is for an external source of energy to perform work on it. More specifically, energy must flow into the system in such a way as to act as an “escalator” that raises the receiving system to a state of higher free energy. Yet, not just any source of energy will achieve this goal. The source must be properly matched to the receiver. In my writing, I have referred to such escalators as engines or energy converters (here, here).
The Need for Information
England goes on to explain how the escalators that life employs are proteins that consist of chains of highly specific sequences of amino acids that cause the chains to fold into the correct three-dimensional shapes. These proteins (e.g., enzymes) can then access chemical energy from energy-currency molecules, such as ATP, and direct it toward target reactions or other processes. He does not mention how energy-currency molecules are generated by complex molecular machines, but these machines are also composed of information-rich molecules.
England details how an organism is continuously bombarded by thermal fluctuations disrupting its structure, so it constantly needs to use chemical energy and information-rich molecules to maintain its operations and to repair damage. He astutely describes such processes in plants:
Like all living things, plants are structures that absorb energy from specific sources in ways that lead to internal motions that correct or undo each incremental bit of falling to pieces that happens at every moment. This process goes on not only when a wound heals, but also much more instantaneously every time sunlight is used to regenerate a molecule of chemical fuel that was just burned up, or every time a molecular chaperone burns up some chemical fuel in order to help a protein that has become misfolded to get back into the correct, functional shape. The fuel-consuming, heat-dissipating activities of proofreading, quality control, and self-maintenance lie at the core of what living things are doing all the time to remain alive, and every one of these activities involves some kind of cyclical motion, whereby work absorbed from the environment perpetually drags things back up the mountain as each little downward slip and slide occurs.
Without these maintenance and repair mechanisms, a cell would irreversibly degrade into an amorphous collection of lower-free-energy molecules.
Up to this point, England and I are in complete agreement. Tomorrow I will indicated where our views diverge.