Physics, Earth & Space
Paul Ashby on Thermodynamics, Information, and Life’s Molecular Machines
I recently watched a very informative lecture by physical chemist Dr. Paul Ashby on thermodynamics, information, and the molecular machines in cells. Ashby is a Staff Scientist in the Molecular Foundry at Lawrence Berkeley National Laboratory, and he is a Director and the Treasurer of the C. S. Lewis Society of California. His academic pedigree includes degrees from Harvard and MIT, and his publications appear in numerous top-tier journals. His talk demonstrates the need for information to be imparted into the highly efficient molecular power generators and energy extractors found in biological systems. I particularly appreciate how his arguments complement my own analyses addressing the origin of life (see here, here, and here).
Ashby begins his lecture by describing the construction of steam-powered locomotive engines. Every component is carefully engineered to ensure that the stream pressure constantly drives the wheels in one direction. He then describes how the energy efficiency of engines has increased from half of a percent in the early 1700s to 54 percent today. The increase resulted from greater ingenuity in the overall design, which includes greater precision in the design of the parts.
The next part of the lecture transitions into a discussion of a thought experiment known as Maxwell’s demon. In the thought experiment, a demon opens and closes a small door between two chambers of gas at specific times to allow only hotter air molecules to travel to one side and only colder molecules to travel to the other. The demon’s actions cause the temperature difference between the two chambers to increase, thus decreasing the entropy, and seemingly violating the second law of thermodynamics. Ashby explains how an agent acting like the demon does not in fact violate the second law since its actions expend energy. This expenditure causes the average temperature of the entire system to rise, so the total entropy still increases. In addition, the demon must be given information about the temperature of the molecules approaching the door to determine whether to open or close it. The information is what allows for the separation of hot and cold gases.
A Functioning Engine
Ashby then connects the discussion about locomotives with the thought experiment by explaining how information is also needed to construct a functioning engine, specifically in the manufacturing instructions. More efficient engines require greater ingenuity and precision of parts, and this improvement entails the instructions containing more information. Thus, efficiency increases with the quantity of information supplied.
Conversely, information can be lost. Machines invariably degrade. For instance, components wear down. Such deterioration corresponds to a loss of information (or specificity) that results in a loss in efficiency. A car must be constantly maintained by repairing or replacing parts, tuning the engine, and aligning the components. Without such upkeep it would eventually cease to function, and the energy from burning the fuel would be entirely dissipated as heat.
Next, Ashby applies the relationship between information and efficiency to biological machines. He notes that machines are more efficient if they operate reversibly, meaning that each small step for the engine frequently works counter to the desired direction. For large machines, such as petroleum engines, reversibility increases for machines running more slowly. But for microscopic machines at the nanoscale, energy flows more easily, so they are more likely to operate reversibly. He then details the operation of ATP synthase and explains how this molecular engine is reversible and operates at nearly 100 percent efficiency. He also describes the series of often reversible chemical reactions in cells that extract energy from food, such as glucose molecules. The extraction takes place in multiple steps, which increases efficiency, and each step is directed by an enzyme. The efficiency and reversibility of the cellular machinery and enzymes entails their containing large quantities of information.
The last part of the lecture explains the implausibility of an undirected evolutionary process ever generating the required information for any molecular machine or series of enzymes. The challenge is that no fitness function or strategy driving a search could find highly improbable targets unless the search algorithm were supplied with information about a target. The underlying theory for this limitation has been explained in detail by Robert J. Marks, William Dembski, and Winston Ewert (see here, here, and here). In other words, the origination of molecular machinery or a set of complex enzymes at the origin of life or in any major evolutionary transformation requires information to be provided from the outside by an overseeing intelligence. Ashby is a committed Christian, so he identifies that intelligence as the God of Jewish and Christian tradition.