Coffee is a popular go-to when you need a quick pick-me-up. But why is coffee so effective at perking us up throughout the day? It's all thanks to the caffeine molecule, its structure and how it functions within our bodies.The structure of caffeine molecules is similar to that of adenosine but produces a very different response in our bodies.

I have a very distinct memory in college in one of my biochemistry classes where I became quite curious about why coffee is so effective in driving sleep away.  

Of course, I knew that coffee contains caffeine, which we all know to be a stimulant, but I wondered why caffeine had this effect in our bodies. There are many different ways in which caffeine affects our brain, but it turns out the molecular structure of caffeine plays a large role in how it functions within our bodies.

If you look at the structural drawing of caffeine, you will notice that it is a combination of two rings, one that is 6-membered and the other that is 5-membered. It is worth noting that these rings also contain nitrogen atoms that are noted with the letter “N” in addition to carbon atoms. 

The overall structure of caffeine shares similar characteristics to a different molecule found in your body called adenosine. Adenosine molecules serve an important function in our brain because an increased level of adenosine tells our brain that we need to sleep and get some rest.  When adenosine binds and activates its receptors that are found on our nerve cells, this activity increases drowsiness and makes us tired.

Adenosine, like caffeine, has a portion within its structure that contains a 6-membered ring and a 5-membered ring joined together. These rings also contain nitrogen atoms just like caffeine.  

These similarities in molecular structure make it difficult for adenosine receptors to distinguish caffeine and adenosine molecules from one another, and caffeine will bind to the adenosine receptors. However, unlike adenosine, caffeine does not produce a cellular response that induces drowsiness when bound to the adenosine receptor, which works to our benefit when we need a quick “pick-me-up” in the mornings and during long drawn out afternoons full of meetings.

There are of course related side-effects of drinking too much coffee or other caffeinated beverages. When the adenosine receptors are blocked by caffeine molecules, your body will trigger adrenaline as a response to this disruption, causing your heart to pound and blood pressure to rise as if you are getting chased by a bear or preparing for a big match.  This is why when the effect of coffee wears off, you may feel more fatigued than ever because your body was in a full alert mode for some time.