From Building Blocks to Biological Polymers
Life depends upon long molecular chains such as RNA and proteins. Origin-of-life research therefore investigates how smaller chemical building blocks could have joined into useful polymers before biological enzymes existed.
The Investigative Question
How could prebiotic chemistry assemble small molecules into longer polymers capable of storing information or performing useful chemical functions?
What We Observe
Modern cells manufacture RNA and proteins using elaborate molecular machinery.
Before such machinery existed, any early informational or catalytic polymers would have needed to form through much simpler chemical processes.
Scientific Background
Polymer formation in water presents chemical challenges because joining molecular units commonly involves condensation chemistry while water can promote the reverse reaction.
Researchers investigate activated monomers, mineral surfaces, wet-dry cycles, chemical activating agents, and other environments capable of encouraging polymer formation.
Why It Matters
Short organic molecules may perform useful chemistry, but heredity and sophisticated catalysis generally require larger structures whose sequence and shape influence their behavior.
The formation of polymers is therefore an important bridge between simple prebiotic chemistry and systems capable of biological evolution.
What Is Known
Experiments have demonstrated several nonbiological routes for producing oligomers and polymers under selected conditions.
RNA-related monomers can polymerize without modern biological enzymes when chemically activated or placed under favorable environmental conditions.
What Is Proposed
Researchers propose that environmental cycling, mineral catalysis, chemical activation, or combinations of these processes produced early polymers from simpler compounds.
What Remains Uncertain
Major questions concern monomer purity, sequence composition, polymer length, chemical activation, competing reactions, degradation, and compatibility with subsequent replication.
Key Numbers
RNA is built from nucleotide units; proteins are built from amino acids. Functional biological polymers can contain hundreds or thousands of linked units, although much shorter molecules can also have chemical activity.
Design Relevance
The formation of polymers provides an important test of whether increasing chemical organization can arise without biological machinery.
For Intelligent Design, the significant issue is not simply whether chains can form, but how polymers possessing useful sequence-dependent functions arose and became incorporated into a reproducing system.
Assessment
Prebiotic polymerization is an active experimental field with demonstrated successes under particular conditions. A complete pathway from realistic mixtures of prebiotic compounds to functional, replicating polymers has not yet been established.