What gives substances their scent? © Getty Images

What gives substances their scent?

Substances generate a smell when their molecules land on olfactory neurones in our noses, but the exact nature of the interaction is somewhat controversial.

Asked by: Jenny Cramley, Basingstoke

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Substances generate a smell when their molecules land on so-called olfactory neurones in our noses (which, for some things, is a pretty unpleasant thought). But the exact nature of the interaction is somewhat controversial. Until recently, it was believed it took the form of molecules physically docking with protein receptor molecules in the walls of the olfactory neurones, like keys fitting into locks. This in turn implied that molecular shape is what determines a specific smell. But this fails to explain why some molecules with similar shapes can smell completely different, while others with quite different shapes can have a similar scent.

These conundrums have led Dr Luca Turin of the Alexander Fleming Research Centre, Athens, to suggest that molecular vibrations are critical. He’s recently published intriguing evidence that molecular shape is not everything by showing that two molecules with identical shape but different vibrational properties can have a different smell.


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