Tag Archives: Chemicals

Color Changes in Chameleons

We have been told that chameleons change their color to conceal themselves by blending in with their surroundings. In fact, a person who is changeable or inconstant in behavior is called chameleon. It has been proved that the facts are something else. And it is a myth. .  Most of the reason chameleons change colour is as a signal, a visual signal of mood and aggression, territory and mating behaviour.

The chameleons are master molecular scientists. Their skin has transparent layers in which different color compounds are tucked away. These specialized cells store the different color compounds and these cells are called chromatophores. They contain various pigments.  These are xanthophores, containing particular specialised pigments that have a yellow colour.  Beneath that are pigment cells which are called erythrophores which have a red colour in them.  Beneath that, another layer of cells called iridiphores have a blue coloured pigment called guanine, which is actually also used in making DNA.  And underneath that is another layer of cells called melanophores which have a brown pigment – melanin – in them.

As such these pigments are confined to sacs. Depending on the signals from the brain, pigments are leaked and depending on the amounts released, mixed colors are formed. This is like artist mixing the different amounts of colors in the color palette. So if you mix red and yellow, you get orange for example, and this is how chameleons do this.  They mix different contributions of these chromatophores.

So a calm chameleon is a pale greeny colour.  When it gets angry, it might go bright yellow, and when it wants to mate, it basically turns on every possible colour it can which shows that it’s in the mood.  This is not unique to chameleons.  Other animals also have these chromatophores. Cuttlefish are another very elegant example of how this works.  So it’s not so much to do with camouflage.  It’s more to do with communication.

Optical Isomerism

Everything is identical about these twins. Number of atoms, type of atoms are same. Only difference is the spatial arrangement of atoms or groups of atoms attached to the carbon atoms. There is one more trait of these twins-they are mirror images of one another. They are called stereoisomers. Stereo means spatial.

There is a slight differences in the reactivity of these members. One very interesting property of these molecules is that they rotate the light passing through their solution in equal and opposite directions called Levo and Dextro.

When such compounds are synthesized in the laboratory, we obtain both isomers in equal amounts and there is no optical activity because effect of one type isomers is nullified by the effect in opposite direction.

But in nature, synthesis of macro-molecules like carbohydrates, lipids and oils by the biological enzyme driven reactions we exclusively obtain only one kind of isomers-mostly levo-rotatary. This is due to enzymes which are proteins and very specific catalysts whereas industrial catalysts are surface active and both isomers are manufactured in equal amounts. Special techniques are required to separate them into pure Levo or Dextro isomers. Due to this reason the cost of these isomers increases manifolds. It has been found that some diseases respond to specific isomers. Such medicine are called stereo-specific medicine.