Explain briefly below how this transition takes place at the molecular level and

Question

Explain briefly below how this transition takes place at the molecular level and the selective advantage this could give to this diving mammal.

Sperm whales are so-named because of the semi-liquid white wax inside their head called spermaceti (Latin for "whale-semen"). Although the liquid was originally thought to be the whale's semen, it turns out it is a complex wax mixture made primarily of cetyl palmitate. High concentrations (several tons) of spermaceti are contained in the sperm whale's head, which makes up a third of their body weight. The biological role of the spermaceti is still somewhat unknown. One hypothesis is that before the whales dive, the cool water passing through the blow hole, cools the wax causing a phase transition. Warming from the head region while underwater reverses this transition.

Explanation / Answer

The spermaceti consists of sterols, esters, and triacylglycerol. Cetyl palmitate (hexadecyl palmitate), an ester of palmitate and cetyl alcohol makes the bulk part of spermaceti. Since, cetyl palmitate is composed of saturated fatty acid hence it packs well and remains solid at low temperatures. In contrast, esters made of unsaturated fatty acids will have a kink in the hydrocarbon backbone that will prevent them from packing in a regular array and hence will be liquid at lower temperatures.

Before the sperm male dives, cold water enters in the whale’s head that causes the blood vessels to constrict leading to reduced blood pressure and temperature. The reduced temperature induces solidification of spermaceti containing cetyl palmitate with a subsequent increase in specific density helping the sperm whale to dive effortless. In contrast, spermaceti is melted while the whale hunts which causes increase in the buoyant density leading to surfacing of whale.

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