Adenosine

Adenosine is a nucleoside — a molecule combining the purine base adenine with a ribose sugar — that plays crucial roles throughout biology and medicine. It's best known as a signaling molecule in the brain and body, where it regulates sleep-wake cycles, energy metabolism, and immune responses. Adenosine builds up in your system during wakefulness; as it accumulates, it binds to adenosine receptors and promotes drowsiness, creating what neuroscientists call "sleep pressure." This is why caffeine, which blocks adenosine receptors, keeps you alert.

Beyond its role as a sleepiness signal, adenosine is a fundamental component of ATP (adenosine triphosphate), the cell's primary energy currency. It also acts as a signaling molecule in countless physiological processes: regulating heart rate, dilating blood vessels, suppressing inflammation, and modulating pain perception.

Medically, adenosine has therapeutic applications — doctors use it during cardiac stress tests to simulate exercise effects on the heart, and it's studied for treating cardiac arrhythmias.

Related

ATP, Caffeine, Nucleotide, Receptor (biology), Metabolism, Circadian rhythm