A review of Nick Lane’s “The Vital Question” is easy to write: just re-arrange a dozen of his own passages. The book itself, though, is not easy to read.
Unless… you understand at least the main principles of physics, chemistry and Latin.
However interesting the author’s main thesis — “I will lay out a hypothesis that connects energy and evolution” — it won’t resonate with those of us who’ve slept through the high school hard science classes, or have erased thermodynamics, electromagnetism and valence from their memory after graduation, the seemingly useless prerequisites for adulthood.
The author promises to describe his point “in enough detail that I can be proved wrong, while writing as accessibly and as excitingly as I can. I’ve tried to avoid unnecessary jargon, and have included occasional reminders of the meaning of terms; but beyond that I hope you will gain familiarity with recurring terms. With the occasional double check, I hope this book will be wholly accessible to anyone who is interested.”
And therein lies the problem. A few pages later, the jovial language of grandeur and metaphor shifts to “isotopic fractionation reported in the graphite inclusions” and hops to the discussion of “prions — perfectly normal proteins that spontaneously refold into semicrystalline structures that act as a template for more refolded prions, where the overall entropy barely changes.”
If you can follow the meaning of the above — hey, congrats, you’ve kept your knowledge sharp and up-to-date. Read on.
“To an absurd first approximation (putting aside the requirement for relatively small amounts of nitrogen, phosphorus, and other elements), a ‘formula’ for life is CH₂O. Given the starting point of carbon dioxide, then life must involve the transfer of electrons and protons from something like hydrogen (H₂) on to CO₂. It doesn’t matter in principle where those electrons come from – they could be snatched from water (H₂O) or hydrogen sulphide (H₂S) or even ferrous iron (Fe₂+). The point is they are transferred on to CO₂, and all such transfers are redox chemistry. ‘Partially reduced’, incidentally, means that CO₂ is not reduced completely to methane (CH₄).
Redox reactions involve the transfer of electrons from a donor (H₂ in this case) to an acceptor (CO₂). The willingness of a molecule to transfer its electrons is connoted in the term ‘reduction potential’. The convention is not helpful, but is easy enough to understand. If a molecule ‘wants’ to be rid of its electrons, it is assigned a negative value; the more that it wants to be rid of its electrons, the more negative is the reduction potential. Conversely, if an atom or molecule craves electrons and will pick them up from almost anywhere, it is assigned a positive value. Oxygen ‘wants’ to grab electrons (oxidizing whatever it takes them from), giving it a very positive reduction potential. All these terms are in fact relative to the so-called standard hydrogen electrode. The point is that a molecule with a negative reduction potential will tend to get rid of its electrons, passing them on to any molecule with a more positive reduction potential, but not the other way around.
At neutral pH (7.0), the reduction potential of H₂ is technically -414 mV. If H₂ gives up its two electrons, that leaves behind two protons, 2H+. The reduction potential for hydrogen reflects this dynamic balance – the tendency of H₂ to lose its electrons, becoming H+, and the tendency of 2H+ to pick up electrons to form H₂. If CO₂ were to pick up those electrons, it would become formate. But formate has a reduction potential of -430 mV. That means it will tend to pass electrons on to H+ to form CO₂ and H₂. Formaldehyde is even worse. Its reduction potential is about -580 mV. It is extremely reluctant to hang on to its electrons, and will easily pass them on to protons to form H₂. Thus, when considering pH 7, Wächtershäuser is correct: there is no way that H₂ can reduce CO₂. But of course some bacteria and archaea live from exactly this reaction, so it must be possible. We’ll look into the details of how they do that in the next chapter, as they are more relevant to the next stage of our story. For now, all we need to know is that bacteria growing from H₂ and CO₂ can only grow when powered by a proton gradient across a membrane.
The reduction potential of H₂ is lower in alkaline conditions: it desperately ‘wants’ to be rid of its electrons, so the left-over H+ can pair up with the OH- in the alkaline fluids to form water, oh so stable. At pH 10, the reduction potential of H₂ is -584 mV: strongly reducing. Conversely, at pH 6, the reduction potential for formate is -370m V, and for formaldehyde it is -520m v. In other words, given this difference in pH, it is quite easy for H₂ to reduce CO₂ to make formaldehyde. The only question is: how are electrons physically transferred from H₂ to CO₂? The answer is in the structure. FeS minerals in the thin inorganic dividing walls of microporous vents conduct electrons. They don’t do it nearly as well as a copper wire, but they do it, nonetheless. And so in theory, the physical structure of alkaline vents should drive the reduction of CO₂ by H₂, to form organics. Fantastic!”
Indeed. If you understand what you’ve just read. Because you can then grasp the book’s main idea.
“All living cells power themselves through the flow of protons (positively charged hydrogen atoms), in what amounts to a kind of electricity – proticity – with protons in place of electrons. The energy we gain from burning food in respiration is used to pump protons across a membrane, forming a reservoir on one side of the membrane. The flow of protons back from this reservoir can be used to power work in the same way as a turbine in a hydroelectric dam.
The use of proton gradients is universal across life on earth – proton power is as much an integral part of all life as the universal genetic code.”
Is it cool? Oh yeah, if that’s your kind of cool. I do like to nerd out about proticity gradients and nanomechanics on my daily 10 K run.
And it is here that I’d include the author’s words of introduction:
“I hope to persuade you that energy is central to evolution, that we can only understand the properties of life if we bring energy into the equation. I want to show you that this relationship between energy and life goes right back to the beginning – that the fundamental properties of life necessarily emerged from the disequilibrium of a restless planet. I want to show you that the origin of life was driven by energy flux, that proton gradients were central to the emergence of cells, and that their use constrained the structure of both bacteria and archaea. I want to demonstrate that these constraints dominated the later evolution of cells, keeping the bacteria and archaea forever simple in morphology, despite their biochemical virtuosity. I want to prove that a rare event, an endosymbiosis in which one bacterium got inside an archaeon, broke those constraints, enabling the evolution of vastly more complex cells. I want to show you that this was not easy – that the intimate relationship between cells living one inside another explains why morphologically complex organisms only arose once. I hope to do more, to persuade you that this intimate relationship actually predicts some of the properties of complex cells. These traits include the nucleus, sex, two sexes, and even the distinction between the immortal germline and the mortal body – the origins of a finite lifespan and genetically predetermined death. Finally, I want to convince you that thinking in these energetic terms allows us to predict aspects of our own biology, notably a deep evolutionary trade-off between fertility and fitness in youth, on the one hand, and ageing and disease on the other.”
Unfortunately, unless you happen to work in biochemistry, physics or mathematics, you’d have to take it all at face value. Really now, Nick, how can we “prove you wrong”? Grab our trusty transmission electron microscope sitting next to our desks? Run a couple of tests on our home DNA sequencer? Bang out some Julia code?
One issue I could sensibly argue about with the author is when he writes: “I’d like to think that these insights might help us to improve our own health, or at least to understand it better.”
Nah. Sorry. The knowledge gap is just too wide for most of us even to comprehend this book, let alone interpret its statements into concrete, life-altering behavior.
The author does hint at — albeit very, very lightly… and using ATP mechanics — aerobic endurance sports contributing to increased life span. But do you need a book about bioenergetics to understand that running and cycling are good for your health?
Good book, wrong audience. Grand vision, highly speculative.
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