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Activation Energy

Minimum energy required to get chemical reactions started

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Fireflies and Flashes

Fireflies and Flashes

Credit: Ted Goldring
Source: http://www.flickr.com/photos/tedgoldring/195785077
License: CC BY-NC 3.0

You have to go out on a really dark night. In an open field, look for the tiny flashes of light, both moving and still. You are witnessing the firefly equivalent of speed dating, where the males only have a certain amount of time to attract a female. He flashes a signal, she responds, and the courtship begins.

Amazing But True

  • Fireflies communicate with flashes of light when searching for a mate. The male does the initial flashing, while the female may or may not flash back. The flashing somehow communicates to the female something about the male that she would find desirable. Whatever that “something” is, the female presumably believes that this male will give her better, stronger offspring that are more likely to survive.
  • Credit: Dendroica cerulea
    Source: http://www.flickr.com/photos/dendroica/4694930376/
    License: CC BY-NC 3.0

    Despite their name, not all firefly have lights. This particular firefly is active during the day and do not need lights [Figure2]

  • The reaction that causes light to form is a biochemical process involving the enzyme luciferase. This enzyme catalyzes a series of reactions involving ATP and oxygen. A complex forms on the surface of the enzyme through a reaction with ATP. This complex then interacts with oxygen to produce a flash of light, releasing products from the enzyme. Unlike light produced by thermal reactions, this light is known as “cold” light since there is no heat generated in the process.
  • The flash rate depends on a number of factors. It has been fairly well established that the temperature has an effect on the flash rate for a variety of firefly species. As the temperature increases, the average flash rate will also increase. This phenomenon makes sense in that the flashing is an enzyme-mediated reaction. An increase in the temperature of any chemical reaction lowers the activation energy needed for the reaction to occur.

Show What You Know

Use the links below to answer the following questions.

  1. How do firefly larvae use flashes?
  2. Do all fireflies flash the same signal?
  3. What is the process called that fireflies use to make light?
  4. What are the final products of the bioluminescent process?
  5. How can the luciferin-luciferase reaction be used to determine the amount of ATP present?

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Image Attributions

  1. [1]^ Credit: Ted Goldring; Source: http://www.flickr.com/photos/tedgoldring/195785077; License: CC BY-NC 3.0
  2. [2]^ Credit: Dendroica cerulea; Source: http://www.flickr.com/photos/dendroica/4694930376/; License: CC BY-NC 3.0

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