How Bioluminescence Works

Bioluminescence is the ability of a living organism to emit light; a phenomenon which has intrigued humans for thousands of years and allowed them to invent mystical and magical stories behind these beacons of light. We might have decided that these lights serve a magical purpose, but evolution has found many uses for this process from protection, all the way to communication.  The chemical mechanism behind these bioluminesent photons is a very simple one, though not the same in all organisms, they share some of the same basic principles.  Taking the firefly as an example, the compound which acts as it's light bulb is called luciferin, and the reaction begins with molecular oxygen and ATP, with the help of the enzyme luciferase, turning luciferin into a dioxetane derivative (mechanism of this can be seen here)¹.

Once this dioxetane derivative is formed the emission of light reaction is ready to occur spontaneously. This happens in a concerted reaction releasing CO₂ and producing an excited ketone. The electron of the excited ketone then falls in energy to create a photon and end with the final product of oxyluciferin.

The newly created oxyluciferin is then enzymatically recycled into luficerin by this mechanism here².

References:
1.  Aldo Roda Chemiluminescence and Bioluminescence: Past, Present and Future, p. 57, Royal Society of Chemistry, 2010, ISBN 1-84755-812-7
2.   Keiko Gomi and Naoki Kajiyama. Oxyluciferin, a Luminescence Product of Firefly Luciferase, Is Enzymatically Regenerated into Luciferin. J. Biol. Chem. 2001 276: 36508-36513. July 16, 2001, doi:10.1074/jbc.M105528200

Why are Flamingos Pink?

This is a question that many children will ask their parents at some point, and if the child is chemically literate this is what the parents could tell them.  Flamingos primarily eat crustaceans and algae from their aquatic environment, which we usually see them standing in, and in their food, there is what is known as carotenoid pigments. Carotenoids are made from fats, and the incorporated into the chloroplasts of algae to serve as light absorbing pigment.  Then the algae get eaten by the crustaceans or flamingos, the carotenoids get passed on into these animals.  Usually when a molecule is eaten, it breaks down, but something such as a pigment will absorb into your bloodstream and not break down, so when a flamingo eats these, the pigments enter the blood stream and then eventually come out in their feathers.  Now for flamingos, the primary pigments which get absorbed and end up in their feathers, are Canthaxanthin (the molecule below), astaxanthin and  phoenicoxanthin ¹. Canthaxanthin is a molecule which gives of a bright violet colour when it is crystallized  but when it is incorporated into flamingo feathers, it is diluted to give a vibrant pink.

References:
1. Fox, D., and T. Hopkins. "Comparative Metabolic Fractionation of Carotenoids in Three Flamingo Species." Comparative Biochemistry and Physiology 17.3 (1966): 841-56.