The Chemical Building Blocks of Life
Living systems are constructed from amino acids, nucleotides, lipids, sugars, and other organic molecules. Origin-of-life research asks how these materials or their precursors could have formed before life existed.
The Investigative Question
Could the basic chemical building blocks needed for life have formed naturally on the early Earth or arrived from other sources?
What We Observe
Living organisms use a comparatively small collection of chemical building blocks to construct proteins, nucleic acids, membranes, and many other cellular structures.
Before the first living system existed, these materials could not have depended upon biological organisms for their production. Some source of prebiotic organic chemistry was therefore necessary.
Scientific Background
Laboratory experiments have demonstrated numerous pathways by which organic compounds relevant to life can form without biology.
Different proposed pathways use atmospheric chemistry, ultraviolet light, mineral surfaces, hydrothermal chemistry, impact chemistry, or extraterrestrial delivery. Modern prebiotic chemistry increasingly investigates reaction networks capable of producing several classes of useful compounds from related starting materials.
Why It Matters
The production of organic building blocks is a necessary early step in any chemical account of life's origin.
However, producing building blocks is not the same as producing life. Those compounds must subsequently be concentrated, selected, assembled, organized, and coupled into systems capable of useful chemical activity.
What Is Known
Amino acids and other organic compounds can form through nonbiological chemistry. Researchers have also demonstrated plausible chemical routes toward nucleotide, lipid, and other biomolecular precursors.
Organic molecules have additionally been detected in meteorites and other extraterrestrial materials.
What Is Proposed
Researchers propose that some combination of terrestrial synthesis, geological chemistry, atmospheric reactions, and extraterrestrial delivery supplied early Earth with organic materials from which more complex chemical systems developed.
What Remains Uncertain
The actual mixture of compounds present on the early Earth is not known. Neither is the relative importance of the many proposed production pathways.
A successful laboratory synthesis demonstrates chemical possibility under the tested conditions, but does not by itself establish that the same pathway occurred during the historical origin of life.
Key Numbers
Life uses amino acids to build proteins, nucleotides to build RNA and DNA, and lipid-related molecules to construct cellular membranes.
Design Relevance
Intelligent Design does not require that ordinary chemistry be unable to produce organic molecules.
The more significant question is what happens after those molecules exist. Can natural chemical processes organize them into a system possessing the information, replication, energy use, and compartmentalization necessary for life?
Assessment
The nonbiological production of many life-related organic compounds is well established experimentally. This removes the need to treat the mere existence of organic building blocks as the central mystery of the origin of life.
The larger problem concerns their organization and integration into a living system.