In a previous article, I discussed the various properties of the carbon atom that make it particularly suitable for biological organisms. But it is not only the carbon atom that is especially fit for life. Though a comprehensive treatment of this subject could fill many volumes, in this article I will offer a brief sample. 

The Properties of the Other Nonmetal Atoms

In an another article, I noted the astonishing life-friendly coincidence that the very atoms from which one can build stable, defined shapes (i.e., the nonmetal atoms carbon, hydrogen, oxygen, and nitrogen) also give the hydrophobic force, which is the key to assembling them into higher-level structures. Another fascinating feature of hydrogen, oxygen, and nitrogen is that their physical and chemical properties are radically different from those of carbon. This diversity facilitates the conferring of unique properties by chemical groups such as amino (NH₂), carboxyl (COOH), and methyl (CH₃) groups.

If these nonmetal neighbors of carbon in the periodic table possessed similar properties to those of carbon — as is the case with the majority of adjacent atoms in the periodic table — then it is doubtful that complex multicellular lifeforms could have existed.

The Electron Transport Chain

The properties of the transition metals are also uniquely fit for their participation in the electron transport chain, which is crucial to the process of cellular respiration. Briefly, the electron transport chain involves the flow of electrons through a respiratory chain. Electrons pass through three protein complexes that are embedded in the inner mitochondrial membrane: NADH-Q oxidoreductase (Complex I); Q-cytochrome c oxidoreductase (Complex III); and cytochrome c oxidase (Complex IV). Complex I, a large multi-subunit protein, is the enzyme that catalyzes the transfer of electrons from the reducing agent (electron donor) NADH to coenzyme Q. The electrons are relayed to cytochrome c at Complex III, and Complex IV transfers the electrons to oxygen, which is thus reduced to water. Complexes I, III, and IV serve as proton pumps, using the energy from electron transfer to transport protons from the matrix into the intermembrane space. The complexes utilize the energy given up by the flow of electrons. The inner mitochondrial membrane is impermeable to protons, leading to their accumulation in the intermembrane space. 

Like water behind a dam, this build-up of protons stores potential energy. A chemical turbine called ATP synthase then facilitates the flow of protons down their concentration gradient from the inner membrane space to the matrix, using the energy released in the process to create ATP. Essential to this process is a unique property of the transition metal atoms, namely, their possessing different redox potentials — that is, their ability to accommodate varying numbers of electrons in their outermost shells. The extent to which the outer shell is full of electrons will determine the atom’s affinity for electrons (with a less full outer shell having a stronger affinity for electrons than one that is fuller). Furthermore, the redox potential (that is, the affinity for electrons) of the transition metals “can be fine-tuned by appropriate choice of ligands to encompass almost the entire biologically significant range of redox potentials.”¹ This makes it possible to organize a chain of transition metal atoms, each with an increasing redox potential, in order for electrons to be drawn from one metal atom to the next in a series of discrete ordered steps. No other atoms, besides the transition metal atoms, have the properties needed to undertake this task. It is also noteworthy that no alternative mechanism has ever been employed in any known lifeform to generate the large quantities of ATP needed to sustain life.

Nerve Impulses

Another instance of prior fitness relates to the suitability of inorganic ions for the generation of nerve impulses in more complex life forms like ourselves. Before an impulse is generated, a neuron is said to be in a state of polarization, with sodium ions (Na+) being more abundant outside the cell and potassium ions (K+) as well as negative ions being more abundant inside. The charge on the inside of the cell membrane is thus negative relative to that on the outside. A stimulus renders the membrane extremely permeable to Na⁺ ions, which rapidly enter the cell (up to a million ions per second can pass through an open ion channel), resulting in a reversal of charges on the membrane (referred to as depolarization). The inside now is positively charged, and the outside negatively charged. Depolarization results in the membrane becoming extremely permeable to K⁺ ions, which rapidly leave the cell. This is referred to as repolarization since it restores the outside positive charge and inside negative charge. Sodium and potassium pumps subsequently return the Na⁺ ions outside and the K⁺ ions inside and the impulse is complete. This process critically depends upon the high mobility of these inorganic ions. Michael Denton observes that “No other small particles of matter possess charge and such great mobility. Neither proteins nor any of the organic molecules in the cell have the right properties to stand in for the alkali metal ions.”²

Designed for Life

If you have read this article along with my other two recent essays (here and here) on the prior environmental fitness of nature for life — and, in particular, advanced life — to exist, it should be becoming clear that the design of our universe to support life extends well beyond the fine-tuning of the laws and constants of the universe. Indeed, an innumerable number of features of the natural world show evidence of purpose and intent. If God exists, it is not at all unexpected that he might fashion a universe capable of harboring complex and advanced lifeforms capable of growing their character and engaging in moral decision-making. On the other hand, if atheism is true, it is wildly implausible that our universe would be conducive to advanced material lifeforms such as ourselves. This overwhelmingly top-heavy likelihood ratio tips the scales in favor of the hypothesis that we live in a theistic universe.

Notes

1. Robert R. Chrichton, Biological Inorganic Chemistry: A New Introduction to Molecular Structure and Function, 2nd edition (Elsevier, 2012), 248.
2. Michael Denton, The Miracle of the Cell (Discovery Institute Press, 2020), 70.