How is chemiluminescence used in biology

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Chemiluminescence / bioluminescence

Chemiluminescence and bioluminescence
Chemiluminescence is the emission of light caused by chemical reactions without a significant increase in temperature. If chemiluminescence is carried out by living organisms, one speaks of bioluminescence. Oxygen plays a central role in the associated biochemical processes.

Presumably, the luminous phenomenon was developed by living beings in order to destroy the former metabolic toxin oxygen. About 3 billion years ago, when the first life developed on earth, the atmosphere had a different composition. There was almost no free oxygen, but the gases nitrogen, carbon dioxide, carbon monoxide, various sulfur and nitrogen oxides, as well as noble gases. So the first life on this planet was inevitably anaerobic. The organisms could not metabolize the oxygen; it was a poison that destroyed sensitive metabolic processes. When the first photosynthetic organisms, the cyanobacteria (or blue-green algae or Cyanophyceae) developed about 2.5 billion years ago, all other organisms were threatened by oxidation by the oxygen produced. Metabolic pathways developed that destroyed this harmful gas inside the cell; one possibility is the generation of bioluminescence. A substrate is oxidized with the help of oxygen to form a reaction product which briefly adopts an energetically excited state: if this transition product changes to the energetic ground state of the reaction product, light is emitted.

Although most living things now need oxygen for breathing, bioluminescence still exists and is used for other purposes. Numerous species generate their own light and use this for camouflage, to catch prey or for communication, for example to identify partners. Some animals generate their own light and can switch it on and off themselves. Others enter into a symbiosis with light-generating bacteria that sit in pockets provided for this purpose. In order to switch off the light, these pockets are covered or darkened.

example

The firefly is probably the best known and the best studied representative of the bioluminescent organisms. His zoological name Photinus pyralis already indicates the production of light. The animal has a bioluminescent substance in the abdomen, the luciferin, which triggers the luminous reaction when an enzyme, the luciferase, is released. The luciferin / luciferase system of the American firefly, a type of firefly, has already been isolated and is used as a detection method in molecular biology.

Frogfish (e.g. Melanocetus johnsoni or Linophryne arborifera) are deep-sea fish that use bioluminescence to acquire food. A bioluminescent organ sits just in front of the mouth. In the deep sea, the prey animals react with a phototaxis, so they move towards the light source with an instinctive light-seeking reaction.

The hatchet (Argyopelecus) has made use of bioluminescence to deceive predators. It has stripes of intensity-adjustable bioluminescent scales on the sides of the body. There are also such scales on the underside of the body. The hatchet fish is a tropical fish that occurs in surface waters. With its bioluminescent strips, it simulates the rays of the sun entering the water, so that it is almost invisible from a distance. From below, too, it is perfectly matched to the water surface thanks to the lighter belly side.