Hoering, Thomas C. Geophysical Laboratory, Carnegie Institution, Washington, DC.
Last reviewed:January 2021
- Tetrapyrrole compounds
- Asymmetrical molecules
- Amino acids
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The study of chemical processes used by organisms that lived in the geological past. Most information on the nature of life in the geological past comes from the study of fossils; a record of biochemical processes that occurred can be found in the organic molecules of sedimentary rocks and fossils. The organic matter in fossil fuel deposits (coal, petroleum, and oil shale) and finely dispersed in shales and limestones represents the debris of cells which have been chemically altered to a more stable form. The relatively reactive organic constituents of cells are subject to bacterial and chemical transformation on the death of the organism. Most organic matter of living organisms is consumed in the metabolism of other organisms and returned to the seas and to the atmosphere. A small amount is deposited in the sediments, where it is preserved or converted to more stable entities. A comparison of the molecular structure of these preserved organic compounds with that of components of living cells enables the researcher to identify similarities and dissimilarities between past and present biochemistry. See also: Fossil; Paleoecology; Paleontology; Petroleum
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