During my freshman year of college, I took two classes in economics: microeconomics and macroeconomics. (I aced both courses, by the way.) Those courses were so much fun that I contemplated becoming an economics major. I’m not sure what the appeal was. Perhaps I was fascinated (and still am) by the idea that mathematical principles exist that can make sense of complex economic systems and I could learn to master those principles. Once discovered, these principles can be marshalled to predict the ways consumers and economies will respond to changes in supply and demand.
This same fascination is one reason why biochemistry is so attractive to me. Like economies, the cell’s chemical systems are incredibly complex. Yet, despite their bewildering complexity biochemists have gained important insight into their structure and function. At times, we can even predict how biochemical systems will respond to environmental and internal cell stimuli.
The Challenge of Predicting Metabolic Pathways
The set of biochemical systems collectively referred to as intermediary metabolism is the pinnacle of biochemical complexity. (See Intermediary Metabolism.) Even though these systems are complex, it is incumbent on biochemists to understand them and be able to predict their behavior. Disturbances in metabolic processes cause numerous diseases. For this reason, metabolic reactions are often drug targets. For drug development to be efficient and successful, biochemists need to know how to predict the response of metabolic pathways when drugs are administered.
Additionally, biotechnologists and synthetic biologists are interested in engineering metabolic pathways so that organisms can serve as bioreactors that produce valuable products (drugs, vaccines, biofuels, bioplastics, etc.) from readily available and inexpensive starting materials. Agricultural scientists also work to manipulate metabolic processes to produce crops and livestock that yield more nutritious foods while thriving under Earth’s changing climate and environmental conditions.
Recently, two biophysicists from Japan made headway toward this end by successfully applying an equation used in microeconomics—the Slutsky equation—to metabolic systems. This equation predicts consumer demand for goods in response to price changes and consumers’ income. It also appears to be able to predict metabolic responses to changes in nutrients or the introduction of metabolic perturbants such as drugs and toxins.1
The principal investigator of the duo found inspiration for the study when he noticed striking similarities between metabolic diagrams and graphical displays used in economics. This topological similarity led him to wonder if economic models could be used to predict changes to metabolic systems when they are disturbed by drugs or deliberately altered through bioengineering methods.2
Their work has important scientific implications and critical utility in biotechnology. It also has provocative philosophical and theological implications. Before I discuss the biophysicists’ work and explore the implications of their findings, a brief primer on intermediary metabolism will be helpful. Those readers well-versed in biochemistry may choose to skip ahead to Microeconomics Predicts Metabolic Perturbations.
It’s not just economies that share commonalities with metabolic pathways, so do interconnected city streets. The chemical reactions that comprise intermediary metabolism are organized like city streets into routes or pathways comprised of a series of chemical reactions. These reactions transform starting compounds into final products via a sequence of
small, stepwise chemical changes. Each step in a metabolic route is mediated by a protein (called an enzyme). The pathways can be linear, branched, or circular.
The chemical components that form part of one metabolic sequence sometimes take part in other pathways. These shared compounds cause metabolic pathways to be interconnected and networked together in the same way that streets form intersections when they come together. The collection of metabolic processes represents a complex, reticulated web of chemical reactions, each one catalyzed by an enzyme.
Microeconomics Predicts Metabolic Perturbations
The two biophysicists demonstrated that operations of economies and metabolism pathways are both described by the Slutsky equation. The equation has two terms: one that reflects the substitution effect and one that reflects the income effect.
The Substitution Effect
The idea behind the substitution effect appears simple at first glance. If the price of a particular good (or service) increases, consumers will buy less of it. If the price decreases, consumers will buy more of it. But it can be more complicated than that. Sometimes when the price of a good drops, consumer demand will remain unchanged. In this case, consumers have more income and decide to use their newfound purchasing power to buy other goods. In some cases, if the price falls, so, too, does the demand for a particular good. In this case, the consumer perceives the item as less valuable or of a lower quality and will purchase more costly items in its place. In the same vein, as the price rises, consumer demand for that good will tend to increase. In this scenario, the consumer perceives the good as more valuable or of a greater quality.
Economists refer to goods that experience an increased demand when prices drop or a decrease in demand when prices rise as normal or ordinary goods. On the other hand, they define Giffen goods (named after Scottish economist Sir Robert Giffen) as goods that display the opposite behavior. Their demand increases as their price increases and falls as their price drops.
The Income Effect
The income effect refers to the impact that a change in income has on the demand for goods. As income increases, consumers gain purchasing power. As income decreases, consumers lose purchasing power. As noted, a change in the price of goods also alters the consumer’s purchasing power. For this reason, the substitution and income effects can work in concert or in opposition to one another.
When a consumer’s income changes, so, too, will the demand they have for particular goods. As with the substitution effect, the change in demand in response to change in income is complex. For example, if a consumer’s income increases, demand for a particular good can increase. In other cases, it may remain unchanged if the consumer redirects his or her increase in purchasing power elsewhere. Or demand may drop if the consumer chooses to use their increased purchasing power to replace the purchase of that particular good with another of better quality.
Biochemical Analogs to Price and Demand
Using insight from microeconomics, the biophysicists decided to treat nutrient availability as income and metabolic “inhibitions” (such as nutrient restrictions, or drug or toxin exposures) as price. Using the Slutsky equation as a starting point, they modified it to correspond to metabolic systems, in which change in demand for a good becomes a measure of metabolic response.
It isn’t surprising that they discovered that many metabolic systems behaved as expected, increasing their flux when more nutrients became available and decreasing their throughput when metabolic inhibitions prevailed. They also discovered scenarios when metabolic output behaved counterintuitively. For example, for certain cancer cells, the rate of metabolic respiration increases when exposed to specific anticancer drugs (which are analogous to a price increase). That is to say, the metabolic change (change in demand) of the cancer cell corresponds to a Giffen good.
The researchers also demonstrated that by using their equations, changes in metabolic output can be predicted simply by measuring the flux of a metabolic system under different nutrient conditions, or when exposed to drugs or toxins. These predictions can be made even if nothing is known at all about the metabolic systems. In other words, these researchers have discovered a fundamental relationship that applies to all metabolic systems. Remarkably, it’s the same relationship that is found in microeconomics, making it a universal law.
This insight by the Japanese researchers has practical utility for drug development and the creation of biotechnologies. It also gives us a better understanding of metabolic systems, and hence, life’s chemistry. Even more important are the interesting philosophical—maybe even theological—implications this scientific advance entails.
The Intelligibility of Nature
It is remarkable that a single, conceptually simple equation universally describes the behavior of metabolic systems and consumer response—both of which on the surface appear to be intractably complex. Making sense of metabolic systems with a single universally applicable equation is a principle that does not stand in isolation. It is endemic to the scientific enterprise. Mathematical laws that capably describe phenomena in our world abound, making nature intelligible to us. This feature is one of the most intriguing aspects of our universe. Nature’s intelligibility is astounding.
For most of the history of science, the discovery and exploration of the mathematical nature of the universe has been confined to physics and, to a lesser extent, chemistry. Because of the complexity and diversity of biochemical systems, many people working in the life sciences have wondered if simple mathematical rules exist in biochemistry and could they ever be discovered. This discovery of a simple rule that predicts the behavior of metabolic systems suggests that mathematical relationships do describe and govern biochemical phenomena.
A universe governed by mathematical relationships suggests that a deep, underlying rationale undergirds nature, which is precisely what I would expect if a Mind was behind the universe. To put it differently, if a Creator was responsible for the universe, as a Christian I would expect that mathematical relationships would define the universe’s structure and function. In like manner, if the origin and design of living systems originated from a Creator, it would make sense that biochemical systems would possess an underlying mathematical structure as well—though it might be hard for us to discern these relationships because of the systems’ complexity.
Even more astounding is our capacity as human beings to make sense of the world around us, and then use that understanding to develop technology and exert some control over nature. Our capacity to understand nature with mathematical precision is what we would expect if human beings have been made in God’s image (as Scripture describes), with the capacity to discern God’s handiwork in the world around us.
But what if humans were cobbled together by evolutionary processes? Why would we expect human beings to be capable of making sense of the world around us? For that matter, why would we expect the universe—including the biological realm—to adhere to mathematical relationships?
In other words, the mathematical undergirding of nature fits better in a theistic conception of reality than one rooted in materialism. And toward that end, the discovery by the two investigators points to God’s role in the origin and design of life.
Is There a Biochemical Anthropic Principle?
The Japanese scientists believe their discovery of a universal, mathematical equation that describes the behavior of metabolic pathways may turn out to be the rule rather than the exception. The two researchers are embarking on a project to determine if other universal laws describing living systems can be found.3
Their discovery also implies that metabolic systems did not arise through the haphazard outworking of evolutionary history. Because a universal law governs the operation of metabolic systems, the structure of these systems appears to be fundamentally dictated and constrained by the laws of nature. In other words, the behavior of metabolic systems appears to be inevitable in a universe like ours.
It is eerie to think that the universe appears to be structured in a just-right way so that metabolic systems—central to life—behave predictably. If the universe was any other way, this may not be the case.
One way to interpret this “coincidence” is to view it as evidence that our universe has been designed for a purpose (the anthropic principle). And purpose must come from a Mind—namely, God.
And you can take that conclusion to the bank.
Resources for Further Exploration
The Optimal Design of Metabolism
The Origin of Metabolism and the Anthropic Principle
Biological Laws and the Intelligibility of Nature
Check out more from Reasons to Believe @Reasons.org
Jumpei F. Yamagishi and Tetsuhiro S. Hatakeyama, “Linear Response Theory of Evolved Metabolic Systems,” Physical Review Letters 131, no. 2 (July 14, 2023): 028401, doi:10.1103/PhysRevLett.131.028401.
University of Tokyo, “The Economic Life of Cells,” ScienceDaily, July 13, 2023.
University of Tokyo, “The Economic Life of Cells.”