The Deep Chemistry of Life and Death
Here is a quote from the Hungarian biochemist Albert Szent-Györgyi: "Life is nothing but an electron looking for a place to rest." Bold statement with a good point, encapsulating the energetics and chemistry that underlies all life.
This is the angle of viewing life on Earth that biochemist and science writer Nick Lane takes in his book Transformer, a whirlwind tour of the Krebs cycle and its longstanding sway over our planet's biotic processes. The opening pages argue that the biological importance of chemical transformations has been unduly overshadowed by the swaths of genomic information in the modern digital era and that "the flow of energy and matter through cells structures biological information rather than the other way around." This is reminiscent of the origins-of-life debate between the genes-came-first camp and the metabolism-came-first camp (and the compartmentalization-came-first camp).
Indeed, the book moves from a portrait of the Krebs cycle and its molecule-level shenanigans to a consideration of the cycle's ancient roots, drawing chemical connections that arc across millennia. Whether carbon fixation via the reverse Krebs cycle or the metabolic chemistry that underlies all lifeforms, carbon is the baton with which life plays relay games, atoms being ferried from one cycle to the next. Stretches of the Krebs cycle could have taken place in the absence of genes and their protein products, driven entirely by inorganic odds and ends like metal ions and sulfate radicals… The story's scope then zooms out to the scale of geologic eras: time is wound back to early Earth. From this panoramic vantage point, Lane reasons through how the Krebs cycle may have driven the sweeping shifts in Earth's climate and menagerie of living organisms (this section is the biochemical companion to another wonderful book we've reviewed on the blog). The focus then shifts to cancer, a disease that is fundamentally more metabolic than genetic, and finally to aging. It is fascinating to see the Krebs cycle as the undercurrent that relates ancient Snowball Earth to anaerobic green sulfur bacteria to our own lifespans.
The book ends with a philosophical encore: how all this biochemistry ties into what defines "self." Lane muses that the proton-motive force is what delineates bacterial cells as individual entities and is in fact what he considers as defining the "self." (A question, then: what of mitochondria?)
It's also a book suffused with personality. Reading about familiar biochemical processes through such a distinctive and personable voice was a novelty to me, and I found even the footnotes fun to read (these were often commentary on science as an institution or scientists' quirks). Lane's enthusiastic intention to make chemistry "approachable" is evident in his tendency to imbue molecules, atoms, and even bonds with personalities, drawing comparisons between molecules like pyruvic acid and the behavior of people. As a non-chemist, I also appreciated the step-by-step diagrams of how gases may have reacted upon charged surfaces to form the molecules of life. It's a prism held up to essential biochemistry (and more) that I would have appreciated in undergraduate classes.
To (Krebs) cycle back to the start of this post, here is a related quote from the book: "Metabolism is what keeps us alive – it is what being alive is – the sum of the continuous transformations of small molecules on a timescale of nanoseconds, nanosecond after nanosecond." Here's to seeing life through metabolism-colored glasses.