Monthly Archives: December 2020

Life’s Beginning – part II

As noted previously there are many descriptions of what is life, but they all require recognition of the need for reproduction. Reproduction however requires adding order to the universe. This reduces something called entropy which can’t happen spontaneously. It doesn’t mean it can’t happen at all, only it can’t happen spontaneously. The way to make it happen is to add energy (synonymous with work.)
A rock will spontaneously roll down a hill, but to get it back up the hill requires work. It’s the same way with chemistry, there are two kinds of reactions: those that go “downhill” and give off energy in the process (exothermic) and those that have to be driven “uphill” by putting energy into the system (endothermic.)

I mentioned entropy as it is an organizing principle in the universe. Entropy is often referred to as “time’s arrow.” You can tell time by watching sand fall through an hourglass. This is a spontaneous process so time is moving in the proper direction.

Back to creating life. We have to have a molecule (or molecular system) that can reproduce itself, but that process is energetically uphill so we need a source of energy to drive the process. The earliest hypotheses about the beginning of life focused on the oceans as a warm chicken soup of ingredients but didn’t address the necessity of an energy source.

Life began during the Archean period, three and a half to four billion years ago. Times were different then. The earth’s surface and atmosphere chemically much different then but there could have been energy-rich molecules and reactions available to drive the self-assembly of life’s molecules.

This is not dissimilar to how life sustains itself today. To build the complex molecules that we need every day requires a process of combining two kinds of reactions. The chemical reactions we need to build protein for example are very endothermic, that is, energetically uphill. If we combine this reaction with one that is energetically downhill, exothermic, we can make it happen. Foods such as fats and carbohydrates can be used to produce the chemical energy (exothermic reactions) we need to drive the endothermic process of protein synthesis.

We need to combine the replication of an RNA-like molecule with certain reactions that give off energy to drive the process. Those ingredients are present around what are called “white smokers.” These are vents in the ocean floor that continuously emit gases that can combine exothermically. Couple these reactions with our RNA-like molecule and everything needed to sustain life is present.

These two approaches to the beginning of life are little more than the reiteration of what sustains life – reproducing molecules, and energy providing molecules. From my perspective, the process is simple and straightforward and therefore is likely to have occurred more than once. Life could have started several times over but ultimately only one survived, as is indicated by the fact that every living thing is related through our DNA. From the smallest bacteria to every plant and animal. We all share the same genetic code and operate on the same principles of reproduction driven by chemical reactions producing energy. In other words, we are one.

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.

Life’s Beginning

This is not about what is life or what is the purpose of life; as a physical scientist, I can only leave those concerns to others such as philosophers and theologians. No, this is about how life came to be. Not how life evolved over billions of years but what happened to turn inanimate chemicals in biology. This is a discussion of the chemistry to biology hypotheses, as there are a couple of them.

The universe is over thirteen billion years old, our planet about four and a half billion, and life here on earth a scant three and a half billion years. So what happened three and a half billion years ago? It depends on which hypothesis to pursue, which requires just a smidgen of consideration of what is life. I have to consider two characteristics of life, reproduction and metabolism. Life is a continuum so obviously you have to continue, but to continue you have energy ie, metabolic energy. The parts necessary for these two activities are different but somehow have to be combined.

The reproductive part of life is absolute and requires other assistive molecules to keep the process going. The most effective hypothesis so far is the “RNA” world. RNA has a structure such that it has to capacity to spontaneously reproduce itself under the right conditions. The neat thing about RNA is that it can not only act to reproduce more of itself, but also and very importantly to simultaneously do those other assistive chores. It can act as a catalyst to speed or retard chemical processes. It’s kind of a one-stop shop for biology. An RNA must spontaneously assemble as a start – no mean feat.

Likely the biggest argument against the spontaneity of life is the improbability of it happening, hence a brief diversion to probability. Take a deck of cards, shuffle, and layout one by one. What is the probability that the first card comes up to what it is? The odds are 52 to I. For the second card the odds that it is what it is, 51 to 1. For just those two cards the probability that they are there and in that order is 52 times 51, hence 2,652 to 1. Run the calculation through your layout and the odds against that happening as you laid them out is approximately 8 followed by 67 zeros to 1. Not so probable, huh? But there it is. An extremely improbable event happened right before your eyes.

Keep in mind that I am talking about the spontaneous beginning of a very simple reproducing bit of matter, much simpler than anything we can see today. I not trying to build a Ferrari here, rather design a simple pushcart, evolution will eventually get me to the race car.

In review, life may have begun with the spontaneous assembly of a primitive molecule such as RNA which has the capacity to both reproduce itself and also catalyze other processes necessary to what we call life, as improbable as that may appear.

In part II, I will explain that I was less than forthright in this first part. These things I have described as spontaneous aren’t. They go against a simple organizing principle of physical reality – entropy. Throughout the universe disorder and randomness reigns, but that doesn’t mean organization doesn’t exist, just that work has to be done to create and maintain that order. Next time, fuel for the Ferrari, stay tuned.

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.