Read the following information carefully and answer the given questions.…
2021
Read the following information carefully and answer the given questions.
Bioluminescence, emission of light by an organism or by a laboratory biochemical system derived from an organism. It could be the ghostly glow of bacteria on decaying meat or fish, the shimmering radiance of protozoans in tropical seas, or the flickering signals of fireflies. The phenomenon occurs sporadically in a wide range of protists and animals, from bacteria and fungi to insects, marine invertebrates, and fish, but it is not known to exist naturally in true plants or in amphibians, reptiles, birds, or mammals. Bioluminescence results from a chemical reaction (chemiluminescence) in which the conversion of chemical energy to radiant energy is direct and virtually 100 percent efficient; i.e., very little heat is given off in the process. For that reason, the emission is called cold light or luminescence. The functional role of bioluminescence in lower organisms such as bacteria, dinoflagellates, and fungi is difficult to discern. Partly because the glow of luminous bacteria is extinguished when oxygen is removed, it has been suggested that the bioluminescent reaction was originally used to remove oxygen toxic to primitive types of bacteria that developed when oxygen was absent or very rare in Earth’s atmosphere. The metabolic reaction that combines the oxygen with a reducing substance (luciferin) liberates sufficient energy to excite a molecule in the organism to emit visible radiation. Most of those luminous primitive organisms subsequently developed systems of using oxygen, but they have retained the luminescent capability as parts of related metabolic pathways or for some survival value that luminescence may confer on the organism.
Which process is responsible for the emission of bioluminescence?
- A.
Conversion of radiant energy to chemical energy directly and virtually
- B.
Conversion of chemical energy to radiant energy directly with a release of a very little heat.
- C.
Conversion of chemical energy to radiant energy indirectly with a lots of heat release.
- D.
Conversion of radiant energy to chemical energy indirectly with a little heat release
Attempted by 24 students.
Show answer & explanation
Correct answer: B
Answer: Conversion of chemical energy to radiant energy directly with a release of a very little heat (chemiluminescence).
Explanation: Bioluminescence is a chemiluminescent reaction in which a chemical reaction (often oxidation of a molecule called luciferin) produces an excited-state molecule. When that molecule returns to its ground state it emits a photon, so chemical energy is converted directly into visible light. The reaction is very efficient, producing almost no heat, which is why bioluminescence is called cold light.
Key points:
A chemical reaction (commonly luciferin + oxygen) creates an excited molecule that emits light (a photon).
The conversion is direct and highly efficient, so very little heat is produced (cold light).
This phenomenon is seen in many bacteria, fungi, marine organisms, and insects (for example, fireflies).
Why the other descriptions are incorrect:
Descriptions that state conversion of radiant energy to chemical energy describe the reverse process (turning light into stored chemical energy), which is not bioluminescence.
Descriptions that claim the conversion is indirect or produces a lot of heat contradict the observed high efficiency and minimal heat release of bioluminescent reactions.