Tag: chirality

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The Problem of Homochirality

The Problem of Homochirality

Can life arise spontaneously from non-living chemicals? Scientists have spent many hours and vast amounts of research money attempting to prove it can. One of the many challenges they must solve is the problem of homochirality.

All the large molecules required to make a living cell are composed of building blocks that have mirror images. When you look in a mirror, you see a reversed image of yourself. The right hand appears to be on the left and vice versa. The right- and left-hand analogy is used when referring to the building blocks of life. Those building blocks come in either right or left-handed forms. We call that handedness “chirality” from the Greek word for hand. Homochirality means having the same handedness.

Life almost exclusively uses only one chirality. The amino acids that make up proteins are left-handed. Scientists are uncertain why, but they have to accept the fact that to build the proteins that RNA and DNA molecules require for life, you must have only left-handed amino acids.

In nature, amino acids are not homochiral. They come in a distribution of about 50/50 left and right, creating the problem of homochirality. For amino acids to form the building blocks of life, they would have to be homochiral. Scientists have yet to find a way to make that happen, even in the laboratory. They aren’t even sure why life requires it since the chemical properties of mirror-imaged compounds are the same for all practical purposes.

The problem of homochirality is one of the many obstacles that prevent non-living chemicals from coming together to form life without intervention by an intelligent force. Even the intelligence of our best scientists has not overcome those obstacles. I saved an Associated Press news release from 2007 titled, “Scientists Believe Artificial Life Will Be Possible in 3 to 10 Years.” We are well past that goal, and I suspect they are not much closer today. 

— Roland Earnst © 2023

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Origin of Life Problems Admitted

Wing Challenge to Origin of Life
One of the more honest and fair writers in modern scientific publications is Dr. Bob Berman. He has a regular column in Astronomy magazine and an interesting website. In the September 2017 issue of Astronomy (page 10), he has an outstanding brief review of the problems involved in trying to explain the origin of life. He begins by pointing out that the definition of “life” has been an issue because of questions such as whether or not a virus is alive. Viruses have no metabolism, they don’t feed or breathe, and yet they reproduce.

Berman then reviews some of the parameters necessary to consider when addressing the origin of life. Chirality is a major issue because amino acids that make up proteins come in right- and left-handed versions. Life on Earth is made up of only left-handed amino acids. Sugars used by the proteins are limited to the right-handed direction, and so is DNA. The wrong chirality just will not work to support life, so how could nature sort out the chirality? If life is easy to produce, why don’t we see it coming into existence all over the Earth? The “amoeba-to-man” model assumes that it only happened once, which conflicts with the view that life is abundant in the cosmos.

What is especially interesting is that Berman raises questions about the ability of evolution to explain on a chance basis some of the designs we see in living things. He uses the example of the airfoil that all flying forms of life have. The upper surface is convex using the Bernoulli effect to produce lift. The earliest bird and the flying reptiles all had a wing design that works. Trial and error would not work well to explain how the wing design would come into existence by chance. Berman points out that “some 400,000 cells would all have to simultaneously mutate in just the right way to create a properly shaped wing. This defies an evolutionary hypothesis.”

Berman concludes with the statement, “I’m not invoking spirituality, merely that the effect of random collisions and mutations is not always a workable answer. So perhaps nature is inherently smart.” I would suggest that wing design is just one of a massive number of design features that allow life to exist.

Berman quotes Francis Crick, the co-discoverer of DNA’s double helix as saying that the origin of life is “almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.” We don’t invent a “god” to explain these things, but we would point to these things as one more evidence that there is a God and that blind chance is not a good designer of the complexity we see in the world around us.
–John N. Clayton © 2017