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How is bioluminescence related to chemiluminescence?

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time-lapse photo of fireflies — Bioluminescence Time-lapse image of fireflies in the Catskill Mountains, New York. Firefly light is a cold light, with approximately 100 percent of the energy given off as light and only a minute amount as heat. Only light in the visible spectrum is emitted.

Bioluminescence is a specialized form of chemiluminescence that occurs within living organisms. While chemiluminescence is a general phenomenon where light is emitted as a result of a chemical reaction, bioluminescence is specifically defined as a reaction catalyzed by enzymes.123

In both processes, chemical energy is converted into radiant energy. However, bioluminescence is remarkably efficient; because it is enzyme-mediated, it can achieve a light yield of nearly 100 percent, meaning almost every molecule of the substrate—known as luciferin—is converted into a radiating state with very little heat produced. In contrast, many non-biological chemiluminescent reactions are far less efficient, often involving only a small fraction of reacting molecules.32

In bioluminescence, the reaction typically involves the oxidation of luciferin in the presence of the enzyme luciferase and molecular oxygen. This process allows organisms to produce what is commonly referred to as "cold light".413