The formation of the large polymers that are characteristic of life may have occurred on the surfaces of clay particles, near hydrothermal vents, or in hot pools at the edges of oceans. RNA may have been the first genetic material and catalyst.
learning outcomes
You should be able to:
Justify the need for catalysts in the origin of life.
Describe the proposed role for RNA in the formation of long-
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Provide evidence supporting RNA as a catalyst in prebiotic chemical reactions that gave rise to other biological polymers.
Why was the ability to both encode information and catalyze reactions important for the origin of life?
A hallmark of living systems is the ability to reproduce, and this occurs from preexisting organisms. The instructions for producing an identical organism must be passed on to the offspring. This implies informational molecules. In living systems, chemical changes constantly occur, but in ordinary chemistry they are too slow to benefit the organism. So catalysts are needed to speed up the reactions.
Why was the discovery of ribozymes important for the development of the “RNA world” hypothesis?
A challenge in developing theories for the origin of life was the need for both a molecule that could carry information and a molecule that could act as a catalyst. Without either, life as we know it could not exist. That an informational molecule, RNA, could also act as a catalyst solved this challenge; ribozymes, also known as catalytic RNA or RNAzyme, are RNA molecules that are capable of catalyzing specific biochemical reactions.
In living organisms, the catalyst for the formation of the peptide bond is an RNA that does not have an informational role. How does this relate to the “RNA world” hypothesis?
Most catalysts in living systems are proteins. But the polymerization of amino acids into proteins that are catalytic must have happened before the protein catalysts were initially formed. Having an RNA, that perhaps was originally informational, act as the catalyst for protein formation solves this “chicken–
The discovery of mechanisms for the formation of small and large molecules is essential to answering questions about the origin of life on Earth. But we also need to understand how organized living systems formed. Such systems display the characteristic properties of life, including reproduction, energy processing, and responsiveness to the environment. These are properties of cells, whose origin we will explore in the next section.