Wednesday, 19 June 2024
The foundation of a living ecosystem vs. Datwinism
An Astonishing Life-Friendly Coincidence: The Properties of the Nonmetal Atoms
Arguably the strongest class of evidence for a cosmic designer is teleological arguments. It is well established that there are far more ways in which the universe might have been that are non-conducive to life than there are life-friendly ways. Given an assumption of theism, it is not particularly surprising that the universe would be hospitable to embodied conscious beings like ourselves. Given an assumption of atheism, conversely, it is wildly surprising that the universe would be supportive of such beings. In light of this significantly top-heavy likelihood ratio, the astronomical rarity of life-friendly universes (and the fact that our universe in fact does support advanced life) tends to confirm theism. One species of teleological argument that deserves more attention is the argument from the prior environmental fitness of nature for the existence of advanced life, which has been popularized in recent years by the work of Michael Denton. Cumulatively, the evidence adduced in Denton’s various books make for a very compelling case that a mind is behind the design of our universe.
Nonmetal Atoms Give Molecules with Shape
One subclass of evidence in this category is the apparent fine-tuning of chemistry for the carbon-based cell, of which you can read in The Miracle of the Cell, by Dr. Denton.1 Here, I will highlight just one example. The figure below shows the periodic table of elements
The elements colored purple in the figure represent the nonmetal atoms, and it is these that make up the material substances of the cell — in particular, carbon, hydrogen, oxygen, and nitrogen. These are in fact the only atoms that could be used to build a biochemical system since they can form strong, stable, directional chemical bonds. Critically, these covalent bonds give molecules with shape, and it is shape that is the essence of biochemistry.
The Hydrophobic Force
Moreover, these atoms have an electronegativity such that the attraction of electrons for hydrogen and carbon is very similar. Since carbon and hydrogen have a similar value of electronegativity (i.e., how strongly atoms pull electrons towards the nucleus), this means that they are able to share electrons equally between the two atoms, creating a nonpolar covalent bond. On the other hand, when oxygen and hydrogen form a covalent bond, you get a polar molecule, where the electrons are shared unequally (specifically, oxygen has a higher electronegativity value, and hence attracts the shared electrons in the bond more strongly than does hydrogen).
This is critical for the whole organization of the cell, because it gives you the hydrophobic force, which is responsible for organizing the higher structure of the biological realm. The hydrophobic force refers to the tendency of nonpolar substances to aggregate in an aqueous environment to minimize their exposure to water. What causes this effect? When nonpolar molecules are introduced into water, it disrupts the structured hydrogen bonding network of water. Water molecules are unable to form hydrogen bonds with nonpolar molecules, leading to an energetically unfavorable situation. To minimize this disruption, water molecules arrange themselves in such a way that they are able to maintain as many hydrogen bonds as possible. To reduce the entropic cost and increase the overall stability, nonpolar molecules tend to aggregate together. By clustering in this way, the surface area in contact with water is minimized, and this reduces the number of water molecules that need to reorganize around them. For this reason, non-polar molecules are also called “hydrophobic” (water-repelling), whereas polar molecules are called “hydrophilic” (water-attracting).
The hydrophobic force is crucial to the assembly of membranes and proteins. Biological membranes are made up of phospholipids, which possess hydrophilic heads and hydrophobic tails. The hydrophobic tails avoid contact with water, whereas the hydrophilic heads interact with it. The result is the self-assembly of the phospholipids into a bilayer with the tails facing inward and the heads facing outward. In like manner, in a protein structure, amino acid side chains that are hydrophobic tend to avoid contact with the aqueous environment. On the other hand, chemical groups associated with polar (hydrophilic) side chains such as hydroxyl (-OH), amine (-NH2) and carboxyl (-COOH) groups form hydrogen bonds with water. The hydrophobic force drives the nonpolar residues to the protein’s interior, while the polar residues are exposed on the surface, interacting with water. This leads to the spontaneous folding of the protein into its native three-dimensional structure, which is crucial for its function.
So crucial is the hydrophobic force to protein folding that biochemist Charles Tanford, describing the discovery of how proteins fold, notes that “[T]he hydrophobic force is the energetically dominant force for containment, adhesion etc., in all life processes… This means that the entire nature of life as we know it is a slave to the hydrogen bonded structure of liquid water.”2
The Hydrophobic Force
Moreover, these atoms have an electronegativity such that the attraction of electrons for hydrogen and carbon is very similar. Since carbon and hydrogen have a similar value of electronegativity (i.e., how strongly atoms pull electrons towards the nucleus), this means that they are able to share electrons equally between the two atoms, creating a nonpolar covalent bond. On the other hand, when oxygen and hydrogen form a covalent bond, you get a polar molecule, where the electrons are shared unequally (specifically, oxygen has a higher electronegativity value, and hence attracts the shared electrons in the bond more strongly than does hydrogen).
This is critical for the whole organization of the cell, because it gives you the hydrophobic force, which is responsible for organizing the higher structure of the biological realm. The hydrophobic force refers to the tendency of nonpolar substances to aggregate in an aqueous environment to minimize their exposure to water. What causes this effect? When nonpolar molecules are introduced into water, it disrupts the structured hydrogen bonding network of water. Water molecules are unable to form hydrogen bonds with nonpolar molecules, leading to an energetically unfavorable situation. To minimize this disruption, water molecules arrange themselves in such a way that they are able to maintain as many hydrogen bonds as possible. To reduce the entropic cost and increase the overall stability, nonpolar molecules tend to aggregate together. By clustering in this way, the surface area in contact with water is minimized, and this reduces the number of water molecules that need to reorganize around them. For this reason, non-polar molecules are also called “hydrophobic” (water-repelling), whereas polar molecules are called “hydrophilic” (water-attracting).
The hydrophobic force is crucial to the assembly of membranes and proteins. Biological membranes are made up of phospholipids, which possess hydrophilic heads and hydrophobic tails. The hydrophobic tails avoid contact with water, whereas the hydrophilic heads interact with it. The result is the self-assembly of the phospholipids into a bilayer with the tails facing inward and the heads facing outward. In like manner, in a protein structure, amino acid side chains that are hydrophobic tend to avoid contact with the aqueous environment. On the other hand, chemical groups associated with polar (hydrophilic) side chains such as hydroxyl (-OH), amine (-NH2) and carboxyl (-COOH) groups form hydrogen bonds with water. The hydrophobic force drives the nonpolar residues to the protein’s interior, while the polar residues are exposed on the surface, interacting with water. This leads to the spontaneous folding of the protein into its native three-dimensional structure, which is crucial for its function.
So crucial is the hydrophobic force to protein folding that biochemist Charles Tanford, describing the discovery of how proteins fold, notes that “[T]he hydrophobic force is the energetically dominant force for containment, adhesion etc., in all life processes… This means that the entire nature of life as we know it is a slave to the hydrogen bonded structure of liquid water.”2
A Fortuitous Coincidence
It is thus a remarkably fortuitous coincidence that the very atoms that yield stable, defined shapes (from which macromolecules can be built) also generate the hydrophobic force which is the key to assembling them into higher three-dimensional forms. Nature does not owe us this life-friendly convergence, and yet if it were not for this coincidence, life could not exist. This is but one of many similar coincidences that are crucial to the existence of life — and, in particular, advanced life. Cumulatively, the evidence suggests that the universe was designed with life in mind.
Notes
Michael Denton, The Miracle of the Cell (Discovery Institute Press, 2020).
Charles Tanford, “How Protein Chemists learned about the Hydrophobic Factor: Protein Chemists and the Hydrophobic Factor.” Protein Science, vol. 6, no. 6, 1997, 1358-1366.
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