Fireflies

From Chempedia

Ann Marie Cumella
Bailey Johnson
Abe Markin
Rania Aburia
Ryan Drury

Contents

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THE CHEMISTRY OF FIREFLIES

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The Chemical Mechanism of Bioluminescence

The process by which fireflies glow is called "bioluminescence," and is defined by Webster’s dictionary as "the emission of light from living organisms."[1] In fireflies, bioluminescence occurs in cells called photocytes that are located in the last one or two segments of the abdomen. Fireflies glow through a two-step series of chemical reactions. In the first step ATP (adenosine triphosphate), an organic chemical called luciferin, and an enzyme called luciferase react to form luciferyl adenylate-luciferase and pyrophosphate. In the second step, luciferyl adenylate-luciferase exergonically decomposes in the presence of oxygen to form oxyluciferin, luciferase, and AMP. The energy released by this second reaction leaves the system in form of photons (visible light).[2] The reaction is presented in the following diagram:

Image:Fireflies_1.gif[3]

Luciferyl adenylate-luciferase is an activated complex containing luciferin, luciferase, adenosine, and one phosphate. It is "activated" because it has received potential energy from ATP and is now ready to release that energy in the form of light. Pyrophosphate is a molecule containing two phosphate atoms and seven oxygen atoms. It has a charge of negative four.[4] Oxyluciferin is the lower-energy, oxidized form of luciferin. Oxygen is the limiting reactant in the second step of the reaction, so fireflies regulate the intensity of the light they produce by controlling oxygen concentration.

Bioluminescence is biologically regulated chemiluminescence that takes place inside a living organism. The basic form of a chemiluminescent reaction has two chemicals reacting to form an unstable, "excited" intermediate product. Since this product is unstable, it lets off energy in the form of light. This can be shown as A+B->[I]*->Products+Light.[5] Where [I]* is an excited state intermediate.

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The Nature and Function of Light Emission by Fireflies

As you can see from the picture below, a common species of fireflies gives off a yellow-green light which has a wavelength of about 550 nanometers.[6] The photocytes contain uric acid crystals as well as the reactants and products involved in the bioluminescent reaction. These uric acid crystals serve to direct the light outward.

Image:Fireflies_2.jpg[7]

The intensity, color, and pattern of light emitted by fireflies vary from species to species. However, across species the purpose of bioluminescence is similar. It is used primarily to attract mates and communicate, as well as deter predators. In some species the light can also be used to attract food. A female firefly can use her body light to mimic the mating techniques of other insects, luring them to her so she can catch and eat them.[8]

Fireflies produce light through a series of chemical reactions, together called bioluminescence, that occur inside cells called photocytes. The first step in the reaction involves the exergonic dephosphorylation of ATP to produce an unstable product. In the second step this unstable product releases energy in the form of photons to become a more stable compound.


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Footnotes

  1. ^ Webster’s Seventh New Collegiate Dictionary, G and C Merriam Company, Springfield, MA 1966
  2. ^ Howstuffworks How Do Fireflies Light Up?. Howstuffworks. 2005. Available at: http://science.howstuffworks.com/question554.htm Accessed October 27, 2005.
  3. ^ Marc Branham. Bioluminescence. 1998. Available at: http://iris.biosci.ohio-state.edu/projects/FFiles/biolum.html Accessed October 27, 2005.
  4. ^ Pyrophosphate. Wikipedia. 2005. Available at: http://en.wikipedia.org/wiki/Pyrophosphate Accessed November 3, 2005.
  5. ^ Simon W. Lewis. Chemiluminescence. Deakin University. 2005. Available at: http://www.deakin.edu.au/~swlewis/cl.htm Accessed October 27, 2005.
  6. ^ Department of Physics and Astronomy, Arizona State University. Reading on Color and Light, Part 1. 1999. Available at: http://acept.la.asu.edu/PiN/rdg/color/color.shtml Accessed October 27, 2005.
  7. ^ Steve Skjold. Available at: [9] Accessed October 27, 2005.
  8. ^ Fireflies in Nature and the Laboratory. Lynn and Gray Poole. Thomas Y. Crowell Company, New York 1965 (p. 24)
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