Biomarkers are characteristics in the body that can be measured and used to determine whether a person's health is normal or abnormal. Biomarkers can be cells, genes, gene products or certain molecules such as enzymes or hormones.

Biomarkers are measurable parameters of biological processes that have prognostic or diagnostic significance and are therefore used as indicators of environmental pollution or disease. They are also used to determine the origin of sediments and the conditions under which they were formed.

In geology, biomarkers or biosignatures are organic substances contained in sediments that allow conclusions to be drawn about their (biological) origin.

A biomarker is a characteristic biological feature that can be objectively measured and can indicate a normal biological or pathological process in the body. A biomarker can consist of cells, genes, gene products or specific molecules such as enzymes or hormones. Complex organ functions or characteristic changes in biological structures are also used as medical biomarkers.

As so-called risk indicators or predictive biomarkers, disease-related biomarkers provide information on whether a disease is imminent, whether it already exists (diagnostic biomarker) or how a disease is likely to develop in an individual case (prognostic biomarker).

Drug-related biomarkers indicate whether and how a drug works in a specific patient and how the patient's organism metabolizes it. In addition to the long-established parameters that are recorded and objectively measured in blood counts, for example, there are a large number of new biomarkers in the various medical disciplines.

Biomarkers are becoming increasingly important in the medical field. They are used to confirm a difficult diagnosis or to make it possible in the first place. A number of diseases such as certain types of cancer, Alzheimer's disease or rheumatoid arthritis are often preceded by an early, asymptomatic stage of the disease. In this phase, biomarkers help to identify symptom-free people at risk in good time and reliably. Biomarkers can be found in blood samples taken by doctors or in urine or saliva samples.

In order to be able to use a biomarker for diagnostics, the sample material must be as easily accessible as possible. This can be a blood sample taken by a doctor, a urine or saliva sample or a drop of blood from the fingertip, which every diabetic takes for regular blood glucose self-measurement.

Of course, a biomarker must be evaluated. The detection method must be accurate and easy to perform, with only minor differences between laboratories. Independent studies must demonstrate the importance of the biomarker for the diagnosis, prognosis and risk assessment of the disease in question.

A biomarker is a substance that indicates the metabolic state of a biological system.

When environmental influences (e.g. solar radiation, lack of water) or foreign substances (e.g. pollutants, pathogens or drugs) enter a biological system, they change the metabolism. This change can be measured by determining the activity of characteristic substances, their presence or their quantity.

Such characteristic substances are usually proteins (e.g. VTG), carbohydrates, hormones or metabolites. A distinction can be made between integral and specific biomarkers. Integral biomarkers can comprise a variety of substances. They generally indicate a range of possible abnormalities. Specific biomarkers, on the other hand, are individual indicators for a specific metabolic step.

Leaves or needles, and often also roots, are removed from plants to obtain the markers. The topic is being researched in a variety of ways and has its origins in ecotoxicology

Geochemical biomarkers are organic substances that are extracted from sediments and can be traced back to specific organisms. They provide information on the origin of the organisms and can be used as an aid to reconstruct climate changes, groups of organisms and the depositional environment in the geological past.

These biomarkers are mainly lipids (hydrocarbons, fatty acids, sterols, hopanoids), as they are relatively stable and can be preserved over geological time periods. The type of substance can provide information about the organism of origin (e.g. algae, land plants).

For example, certain ketones (alkenones) are produced by certain marine algae and long-chain n-alkanes (with more than 25 carbon atoms) are synthesized in the leaf axils of higher plants. In addition, the presence of some substances such as diploptes (bacterial markers; cyanobacteria) also provides information on biological processes at the time of sediment deposition.

The isotope ratio of carbon and hydrogen can be measured on biomarkers in order to obtain information about the origin of a substance. The ratio of stable isotopes, especially of carbon and hydrogen, is often measured on these biomarkers in order to obtain information about the origin of the substance. For example, the carbon isotope can provide information on biological processes (e.g. photosynthesis), while the hydrogen isotope can provide information on climatic influences (e.g. moisture or drought) at the time the substances were formed. If the sediment is altered by the influence of temperature and pressure after it has been deposited, relatively stable biomarkers also change. It is then no longer necessarily possible to draw conclusions about the original biological substance and this is also referred to as geomarkers.
In the search for extraterrestrial life, astrobiologists look for a biosignature. These are gases or molecules that can indicate the presence of life on an exoplanet or exomoon. For example, oxygen in the atmosphere could be considered a biosignature, as it is produced by plants and other organisms on Earth.

Astrobiologists also use spectroscopy to analyze the light from stars and galaxies to determine if they contain elements that could indicate life. These elements include carbon, hydrogen, nitrogen, oxygen and iron - all of which are necessary for the existence of life as we know it on Earth.