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Quantum mechanics seems to play a crucial role in the atomic world.
Great deal you might say. Quantum mechanics is for theorists that want to dig into the atomic world.
This is not true. If it wasn’t for quantum mechanics life would not even exist. Quantum mechanics is a model of how things in the atomic scale behave but these quantum mechanisms affect the macro scale from the bottom up.
The most impressive of all is that scientists are starting to realize that nature has used the quantum weird behavior and exlpoited it to create effective systems that are embedded in live creatures.
One great example is a model of our smell. Prior theories have proposed a key and lock mechanism (very common to theories in biology and medicine). This model suggests that if an odor molecule finds the correct receptor that has complementary shape then it ignites the smell. Look the image below. 
Nevertheless, there are some important features of smell that this model could not explain. For example, how molecules with the same shape smell very differently? This fact renders the model above useless.
In 1997 Luca Turin proposed a different model for the smell. He proposed that electrons from the odor receptor, tunnel through the molecule with the correct, analogous to the receptor, vibration. This tunneling causes the nerve attached to the receptor to ingite and produce the signal that brain interprets as smell.
Tunnelling effect is a quantum phenomenon where an electron due to its wave matter properties can surpass an energy barrier that classically would not have the energy to pass over. The probability is low but the tunnelling is possible. It is like you passing through a wall! (of course you are not electron 
This is a much more robust model that explains the phenomenon of almost same molecules producing different odor. We know that even an atom could cause a shift in the vibrational modes of a molecule and thus produce a different energy barrier. If a molecule differs in a single atom from another, then the tunneling will not happen in the receptor causing the receptor not to fire signals to the brain. This explains the selectivity of the receptors for almost the same molecules. The tunneling of the electrons depends on the interaction and the energy barrier created by the molecule and the receptor combined.
We see now how important is quantum mechanics to our everyday life. QM will play crucial role in the future as we explain more and more biological phenomena that quantum weirdness comes into play. In another article I will write about the quantum mechanics interpretation of consiousness and brain function as Prof. Nanopoulos has imagined it and the importance of quantum mechanics in photosynthesis which is the source of life in our planet.
If you want more technical details about the QM model of smell you may download the original article here
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