We all know those mornings. You stayed up too late studying, playing video games, or binging your favorite series. You wake up drowsy and distressed, then remember you have a test today. For a moment you panic, but you quickly realize you have the luxury of indulging in a hot cup of coffee. Your preconceived impression is that the coffee will cure your exhaustion– it’s almost too good to be true. Suddenly, you notice that you have become reliant on a beverage to take the place of quality sleep several days a week. But is this notion accurate? How well can caffeine mask a lack of sleep?
The reason people feel drowsy at any time of the day is due to a buildup of adenosine in the bloodstream. Adenosine is produced when the body consumes its central energy source (ATP). Adenosine in the bloodstream binds to adenosine receptors. Once bound, these receptors trigger a release of proteins that inhibit neuron activity, leading to drowsiness.
Caffeine’s solution to the abundance of adenosine acts as a temporary patch-up. Caffeine has the ability to block adenosine receptors, therefore preventing adenosine from causing drowsiness. The problem, however, is that caffeine does not stay bound to adenosine receptors for very long, so tiredness will likely kick in at some point later in the day. Since caffeine is just “patching up” the problem, it will never be nearly as effective as sleep which allows for the breakdown of adenosine.
I have noticed the effects of caffeine are much greater later in the day compared to consuming it in the morning. This is because caffeine tends to raise cortisol levels. Upon waking up, cortisol levels are already high. It is also the case that adenosine levels grow as the day progresses. These two factors explain why caffeine has stronger effects later in the day. There is a more drastic change caused by caffeine on cortisol levels and the “control” of free adenosine.
I found the process of caffeine binding to adenosine receptors to relate to our cell communication unit. When caffeine enters the bloodstream, it acts as a competitive inhibitor by preventing adenosine from binding. A competitive inhibitor takes the place of a substrate in an enzyme directly at the active site. This prevents a chemical reaction from occurring. In this case, caffeine is blocking a receptor that causes drowsiness when activated. If caffeine is blocking it, adenosine which would have caused drowsiness is unable to attach to the receptor. If the adenosine were to attach to this receptor, it would trigger a signal that is sent through neurons to cause the sensation.