Classroom for Geology and Disaster

What is a biomarker

What is a biomarker
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What is a biomarker?

Molecular biological markers, or biomarkers, are natural products that can be traced to a particular biological origin. They are powerful tools that can be used to trace diseases, drugs, and environmental contaminants in modern systems.

In our group, however, we use them to study ancient environments and the evolution of life on Earth. The most effective biomarkers/biomarkers are/are organic compounds with specific biological sources, whose structures can be preserved through geologic time.

What is a biomarker
Fig: A few examples of lipids (Wikipedia Commons)

Reconstructing early life from organic matter

Molecular fossils that are stable under geological conditions mostly originate from biological lipids. Lipids are a group of molecules that include fats and waxes, and they generally preserve better in sediments over long periods than molecules like DNA and proteins. These biomarkers encode information about ancient biodiversity, food chain associations, and environmental conditions.

They are recorders of element cycling, sediment and water chemistry, oxidation-reduction conditions, and temperature histories. Most importantly, however, hydrocarbon biomarkers are stable for billions of years if they are enclosed in intact sedimentary rocks that have only suffered a mild thermal history (i.e. haven’t been heated up very much). Therefore, biomarkers offer a powerful means of studying geobiology—life and its interaction with the environment.

Structural and isotopic information allows them to be distinguished from abiogenic (non-living) organic compounds that exist throughout the cosmos. Thus, biomarkers are also an important tool in searching for extraterrestrial life elsewhere in the universe.

How biomarker is created and preserved in the geologic record

With that introduction, we can begin to get to the biological and geological processes that create and preserve biomarkers. Below is a geologic timescale from the beginning of the formation of the earth to the present day, which shows you what we have learned about the evolution of life through studying biomarkers.

What is a biomarker
Fig: Age distribution of sediments from well-preserved organic matter; adapted from Treatise on Geochemistry review, Vol. 8, Chapter 3; Brocks and Summons

Biomarkers can be classified in this section read more to learn the types of biomarkers>>Biomarker classification

The lipids are the main source of all biomarkers hence it is generated from the lipids. Learn more from this section >>>Lipids

Some of the lipids are acetogenic lipids which are like alcohol, and cholesterol which do not dissolve in the water. Learn more from this section >>>>Acetogenic lipids

In this section learn more about the Isoprenoid. They are classified into

>>>>Acyclic and cyclic isoprenoids

>>>>Polycyclic isoprenoids

Hence learn more about the >>>>Isoprenoids

In  this section, you can learn more about hopanoids>>>>Hopanoids,  hopanes

Learn more about the steroids. It is one of the important biomarkers in the geologic study>>>>Steroids, Steranes

Those biomarker has a larger Carbon number in the hopanoid ring hence the name carotinoid>>>>Carotenoids


This is the source of all biomarkers>>>Kerogen

The process of forming biomarker >>>Diagenesis and catagenesis

Biomarkers can identify the source of any production of biomarkers. Learn more from this section >>Biomarker as Source Indicator

What is a biomarker and hydrocarbon?  How it is linked with the biomarker or the molecular fossils? Learn more from this section >>>Hydrocarbons

>>>Environmental Indicators

>>>Indicators of Euxinia

>>Experimental methods to extract biomarkers

>>>Source rock