Bioluminescence

Bioluminescence is a type of luminescence resulting from the production and emission of electromagnetic radiation by living organisms. Bioluminescence, meaning “living light,” occurs in a wide variety of creatures, from bacteria and fungi to fish, and insects. Unlike artificial light sources, bioluminescence doesn’t involve heat generation but involves a chemical process within the organisms themselves.

  • The chemistry behind bioluminescence lies in a special molecule called luciferin. When luciferin reacts with another molecule, usually an enzyme called luciferase, in the presence of oxygen, energy is released. This energy takes the form of visible light, creating the characteristic glow. Different luciferins and luciferases determine the emitted light’s colour and intensity.
  • Marine organisms including single-cell dinoflagellates, some jellyfish and the deep sea anglerfish use the luciferin-luciferase reaction to release energy as blue-green light.
  • Terrestrial Organisms including fireflies and glowworms also use the luciferin-luciferase reaction to create light.
    • Fireflies have a specialized light organ that contains luciferin and luciferase. The reaction involves adenosine triphosphate to provide the energy to excite an electron in the luciferin, which then emits a photon upon returning to its ground state.
    • Glowworm larvae of various fly and beetle species possess luciferin and luciferase and produce a similar light-emitting reaction.

Materials Involved in Bioluminescence
  • Luciferin: This small organic molecule acts as the fuel, with different variations depending on the organism. It’s the source of the chemical energy that gets converted into light.
  • Luciferase: This enzyme acts as the catalyst, speeding up the reaction between luciferin and oxygen. Different luciferases determine the colour and intensity of the emitted light.
  • Oxygen: Although not universally used, oxygen serves as the final electron acceptor in most bioluminescent reactions, stabilizing the energy released and enabling light emission.
  • Adenosine Triphosphate (ATP): In some systems like fireflies, ATP provides the initial energy boost to excite the electron in luciferin, kicking off the bioluminescent reaction. However, in these systems, the excited electron ultimately interacts with oxygen as the final electron acceptor, similar to systems that use oxygen directly.
The Bioluminescence Process
    • Excitation: The luciferase enzyme interacts with luciferin, either directly using energy from ATP (fireflies) or indirectly drawing energy from sunlight or chemical reactions with the organism (dinoflagellates). This interaction excites an electron in the luciferin molecule, raising its energy state.
    • Electron Transfer to oxygen: In most bioluminescent reactions, the excited electron in the luciferin molecule doesn’t directly emit light. Instead, it transfers its energy through a series of steps, ultimately reaching oxygen as the final electron acceptor.
    • Energy Release: During this transfer, some of the released energy is channeled into a specific form suitable for light emission. This specific energy then triggers the luciferin molecule to emit a photon (light).
    • Light Emission: Upon releasing this converted energy as a photon (light), the excited molecule returns to its ground state.
    • Variations: While the basic principle remains similar, specific molecules, reaction pathways, and light colours can vary significantly depending on the organism and its unique bioluminescent system.
Electron Excitation in Bioluminescence
  • Imagine an electron within the luciferin molecule orbiting its nucleus, like a ball at the bottom of a hill. This is the ground state, where the electron has its lowest energy.
  • During the bioluminescent reaction, the luciferin molecule receives energy from different sources depending on the organism:
    • Fireflies: The luciferase enzyme uses ATP to directly excite the electron, pushing it to a higher energy level.
    • Dinoflagellates: Light or chemical reactions interact with luciferin, indirectly causing electron excitation.
    • Once energized, the excited electron jumps to a higher energy level within the luciferin molecule. This excited state is unstable, and the electron wants to return to its ground state.
    • However, it doesn’t simply drop back down. Instead, in most bioluminescent organisms, it transfers its energy through a series of steps to oxygen, the final electron acceptor. The excited electron doesn’t physically jump to oxygen but interacts with it indirectly through the molecule chain, ultimately transferring its energy.
    • During this transfer, some of the released energy gets converted into a specific form suitable for light emission. Finally, this converted energy triggers the emission of a photon from the excited molecule (often luciferin itself), releasing the remaining energy and bringing the electron back to its ground state.
Light SourceDescriptionSub-atomic ProcessMechanismVisible LightNaturalArtificial
luminescenceAny process where atoms or molecules emit light. See Bioluminescence, Chemiluminescence, Electroluminescence,
Fluorescence
Electron ExcitationVarious mechanisms involving energy transitions in atoms/moleculesVaries (depends on mechanism)Yes (some mechanisms)Yes (various technologies)
BioluminescenceA form of luminescence:
Light emission by living organisms
Electron Excitation
Chemical reactions initiated and controlled by biological systems within living organisms.YesYesYes
ChemiluminescenceA form of luminescence:
Light emission from chemical reactions
Electron Excitationhemiluminescence relies solely on the chemical energy stored within the reacting molecules.Varies (depends on reaction)Yes
(natural and synthetic)
Yes (glow sticks, analytical tools)
ElectroluminescenceA form of luminescence::
Light emission due to electric fields
Electron ExcitationApplied electric field excites electrons in materialsYesNoYes (LEDs, displays)
FluorescenceA form of luminescence:
Light emission from certain materials after absorbing light
Electron ExcitationTemporary absorption of light, followed by emission of a different (lower energy) color.YesYes
(minerals and plants)
Yes
(dyes, pigments, glow sticks)
Photoluminescence
Light emitting diodeA type of electroluminescence
Semiconductor diode emitting light when current flows
Electron transition
(recombination)
Recombination of electrons and holes in semiconductors releases energy as photonsYesNoYes
Lasers
(Light amplification by stimulated emission of radiation)
A type of photoluminescenceLight amplification by stimulated emission of radiationExcited atoms/molecules release photons, stimulating further photon emission and amplifying lightYesNoYes
Stellar lightNuclear fusionFusion of hydrogen nuclei releases enormous energy, including lightYesYesNo
FireChemiluminescence & Blackbody radiationHot objects emit light (incandescence), and chemical reactions create excited molecules (chemiluminescence)YesYesYes
LightningPlasma processesHot, ionized gas (plasma) emits light through various mechanisms like recombination and BremsstrahlungYesYesNo
Neon signsGas dischargeElectric current excites gas atoms, which emit light upon returning to lower energy levels (similar to fluorescence)YesNoYes
Light bulbs (Incandescent)Blackbody radiationHot filament emits light due to thermal excitation of electronsYesNoYes
SunlampsUltraviolet radiationEmit UV light, causing fluorescence in nearby materialsNo (UV)NoYes
  • Bioluminescence, meaning “living light,” is the production and emission of light by living organisms. It occurs in a wide variety of creatures, from bacteria and fungi to fish, insects, and even some deep-sea animals. Unlike artificial light sources, bioluminescence doesn’t involve heat generation, making it a truly cold light.
    • The chemistry behind bioluminescence lies in a special molecule called luciferin. When luciferin reacts with another molecule, usually an enzyme called luciferase, in the presence of oxygen, energy is released. This energy takes the form of visible light, creating the characteristic glow. Different luciferins and luciferases determine the emitted light’s colour and intensity.
    • Whilst the light is what we see, bioluminescence is a complex biological process.
    • The materials involved in bioluminescence include:
      • Luciferin: The “fuel” molecule, often a small organic molecule with a specific chemical structure depending on the organism.
      • Luciferase: The “spark,” typically an enzyme that acts as a catalyst, accelerating the reaction between luciferin and oxygen.
      • Oxygen: Essential for most bioluminescent reactions, acting as the final electron acceptor.
    • The reactions involved in bioluminescence include:
      • Activation: Luciferase activates luciferin through various mechanisms, depending on the specific type.
      • Oxidation: Oxygen reacts with the activated luciferin, transferring energy to an excited state.
      • Light emission: As the excited molecule returns to its ground state, energy is released as visible light with a specific wavelength determined by the energy change.