How we smell: competing theories © Getty Images

How we smell: competing theories

Surprisingly, the mechanics of how we smell things and recognise odours still aren’t fully understood.

US scientists Richard Axel and Linda Buck won the 2004 Nobel prize for their groundbreaking work in this field.

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They discovered that 1000 different genes – that’s about three per cent of all our genes – code for smell receptors in our noses. But not everyone subscribes to their lock and key theory…

Shape theory

This represents the current orthodox thinking in the world of smell recognition – and it has done for some 60 years. Here, part of an odour molecule – the ‘key’ – docks with a receptor in the upper part of our nose – the ‘lock’. This chemical interaction is converted into an electrical signal that travels to the olfactory bulb in the brain.

Several receptors corresponding to one scent send signals to one location in the bulb. Then information from several of these areas is relayed to other parts of the brain where the information is combined – forming a pattern. Nobel laureates Richard Axel and Linda Buck have been the main champions of the shape theory, uncovering how the receptors in the nose link with the brain.


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