How firefly emits light?

How firefly emits light?

PROF WAQAR HUSSAIN

           Fire flies are winged beetles of insect family, comprising of 2000 species. Fire flies are also known as glow worm and light bug because they produce cold light of wavelength 510 to 670 nanometers. Light is produced due to a process called bioluminescence occurring in the cells of its lower abdomen with the help of a chemical luciferin(light bearer) which under goes enzyme catalyzed oxidation and an “intermediate” is formed in excited state that when returns to ground state, emits light. This light emitting process proceeds in two reactions:  

First, luciferin combines with adenosine triphosphate(ATP) to form luciferyl adenylate and pyrophosphate(PPi) in the presence of magnesium ions on the surface of enzyme luciferase.

              

(1) Luciferin + ATP  Luciferyl adenylate + PPi

Second, luciferyl adenylate combines with oxygen to form oxyluciferin and adenomonophosphate(AMP) and light is produced.

             (2) Luciferyl adenylate + O₂   Oxyluciferin +AMP+Light

   The light producing cells also have crystal of uric acid which reflects the light away from the abdomen. Fire flies have no lungs thus oxygen is supplied. through special tubes called trachea. The switching of light on and off is controlled by nerve cells or oxygen supply.