Download A9-B16 REWRITE The Wonders of Bioluminescence During the day

A9-B16 REWRITE
The Wonders of Bioluminescence
During the day, the main source of light is from the sun. At night, light comes mainly
from the moon and stars or from street lamps and homes when in a city or town. Animals such as
fireflies, glowworms, click beetles, jelly fish, squid, and many more even appear to glow. These
creatures produce their own light through a type of chemical reaction known as bioluminescence.
Understanding how luminescence works provides valuable information for these animals and
humans. In addition to having evolutionary benefits to creatures that emit it, bioluminescence
acts as a valuable tool in the field of biological research.
I would add a paragraph or two about bioluminescent organisms. Try to include where
they are found and perhaps whether they acquire or produce the chemicals necessary for the
chemical reaction. Adding a little history/background information to the chemistry will make the
essay more interesting.
In bioluminescence, a living organism produces and emits light as a result of a reaction
that converts chemical energy to light energy. The components involved in the production of
light in a firefly, for example, include luciferin, adensosine triphosphate (ATP- the general
source of energy) and also molecular oxygen, O2. Luciferase or luminase are generic terms for
enzymes that catalyze the process of bioluminescence in nature and are also involved in the light
production of a firefly. Luciferase catalyzes a variety of reactions using a variety of different
substrates. In fireflies, luciferase catalyzes an oxidative reaction involving ATP, luciferin and
molecular oxygen. The result of the reaction yields an electronically excited oxyluciferin species.
One proposed mechanism of the luciferin-luciferase reaction is that luciferin’s
carboxylate group is activated by reaction with ATP to form the adenylated luciferin. Then the
alpha subunit is lost, allowing the reaction with molecular oxygen. Cleavage of the dioxetanone
ring yields the excited state of oxyluciferin. What are the other proposed mechanisms?
The catalytic mechanism of firefly luciferase.
Firefly luciferase acts not only as a mono-oxygenase but also a synthetase to generate the
acyl adenylate. The catalytic mechanism of firefly luciferase is a multi-step process:
Step 1:
The firefly D-luciferin is transformed to the enzyme-bound luciferyl adenylate, releasing the
inorganic pyrophosphate when ATP and magnesium are present. The adenosine monophosphate,
AMP, is the substrate for the oxidation of firefly luciferase.
Step 2:
Although the firefly luciferase functions as the mono-oxygenase, it behaves in a very unusual
manner without the apparent involvement of a metal or cofactor. The oxygen generates a ringed
species which later transforms into the electronic excited state and yields the carbon dioxide. The
excited state of Luc⋅ Oxyluciferin and the carbon dioxide each contains an oxygen atom from
molecular oxygen.
Step 3:
The rapid loss of energy of the excited Luc⋅ Oxyluciferin to its ground state emits light through
the pathway of fluorescence. The resulting light, the firefly’s signature glow, is extremely
efficient meaning that the majority of the energy put into the system is emitted as light rather
than heat. Also known as "cold light," bioluminescence is ninety-six percent efficient, far more
efficient than an incandescent light with an efficiency rating of only ten percent. This efficiency
is due to the fact that nearly every reacted Luciferin emits a photon. At the same time, fireflies
can also use dehydroluciferin to yield the acyl adenylate and inorganic pyrophosphate. This step
which has no further steps is considered as the limitation step for step 1 to inhibit the activity of
the enzyme. All known bioluminescence reactions require oxygen and the intermediacy of
peroxides, however luciferases constitute a diverse group of unrelated enzymes acting upon
chemically different luciferins and employing a variety of cofactors.
The mechanism of bioluminescence is made even more interesting due to the fact that it
is a naturally occurring reaction which is controlled by the organism itself. The ability of fireflies
to control the rate at which they emit light is explained by two theories: the Oxygen Control
Theory and the Neural Activation Theory. As mentioned previously, oxygen is required in the
production of light. The Oxygen Control Theory explains how fireflies are able to regulate the
amount of oxygen they intake, therefore controlling the rate at which light is emitted. The Neural
Activation Theory, on the other hand, explains how fireflies have structures called tracheal end
cells, that are neural controlled and facilitate the chemical reaction. (As a reader, I found myself
wanting more information about these two theories. Who came up with them? How do fireflies
control the oxygen? How do neurons control the reaction? Which theory has more evidence in its
favor? Adding this information would definitely make the paper a lot more interesting)
The signature glow of fireflies is useful for several different reasons. The larvae, for
example, use their glows as warning signals to communicate their distastefulness to predators.
As adults, many fireflies have flash patterns unique to their species and use them to identify
other members of their species as well as to distinguish between members of the opposite sex.
Several studies have shown that female fireflies choose mates depending upon specific male
flash pattern characteristics. Higher male flash rates, as well as increased flash intensity, have
been shown to be more attractive to females in two different firefly species (citation?)
Knowing the mechanisms for bioluminescence has allowed many scientists to take
advantage of this property and use it as an aid to other areas of study. For example,
bioluminescence researcher Christopher Contag came up with the idea of using bioluminescence
as an indicator of life for a particular specimen. (A specimen of what?) This is due to the fact that
bioluminescence depends on the presence of ATP, a primary component of living organisms.
NASA also considered using this technique to determine the possibility of past lives in other
planets by testing for ATP in planet samples. More detail on these research examples would be
useful.
Not only is bioluminescence a reliable indicator of life, it also serves as a good biomarker.
Luciferase was added to tuberculosis samples along with the antibiotic to test the antibiotic’s
strenghth. Stronger antibiotics would present with a low light due to the reduction in bacterial
growth. On the other hand, weak antibiotics would present as a glow when luciferase reacts with
oxygen and ATP indicating presence of live bacteria. (Citation? Who ran this experiment? What
antibiotic was it?) Green fluorescent proteins (GFP) from jellyfish are also great markers for
determining the location of proteins. When hit with blue light, GFP glows green. Therefore,
proteins of interest may be detected by staining cells with fluorescently labeled antibodies.
Bioluminescence is a natural wonder so amusing, yet sometimes forgotten. By exploring
the production and the different purposes of bioluminescence among organisms like the firefly,
one can appreciate the natural beauty that our earth has to offer us. As researchers, we have only
just tapped into the wonders of bioluminescence, and many opportunities for research and use
certainly lie ahead.