Adenosine is a naturally occurring organic compound that is important to the biochemistry of living organisms, including humans. It also helps to regulate arousal and sleep and protect cells from damage. Additionally, it is a component of several larger, related molecules with important functions such as intracellular messaging and providing energy for metabolism. In medicine, it is also sometimes given intravenously to treat heart conditions. Its chemical formula is C10H13N5O4.
It is a type of chemical called a purine nucleoside, a term describing its molecular structure. Purine compounds are composed of two linked ring-shaped structures of atoms called aromatic rings, which have unusually high chemical stability. A nucleoside is a compound in which a compound called a nucleobase, or simply a base, is bonded with a molecule of either ribose (C5H10O5) or deoxyribose (C5H10O4), both of which are simple sugars or monosaccharides. Adenosine consist of ribose combined with the purine adenine (C5H5N5).
The amount of the substance in the body gradually increases during waking hours. Due to its inhibitory effect on the nervous system, this eventually begins to cause drowsiness and finally sleep, at which point the amount of the chemical in the body starts dropping again. Part of the reason for the effectiveness of caffeine (C8H10N4O2) as a stimulant is that caffeine can bind to the same receptors in cells and so interferes with the normal effects of high adenosine levels. Adenosine levels in the bloodstream also increase significantly in areas suffering from inflammation or restricted blood or oxygen supply, where the chemical helps to decrease inflammation and prevent cell damage.
Several important chemicals in the body are composed of adenosine combined with one or more phosphate groups. Adenosine monophosphate (C10H14N5O7P) is a type of chemical called a second messenger, which transmits chemical messages from the exterior of his cell to the interior. Adenosine triphosphate (C10H16N5O13P3), or ATP, is an important source of chemical energy for the body and powers many metabolic processes with the energy released when its chemical bonds break down. Adenosine diphosphate (C10H15N5O10P2) is produced by the breakdown of ATP and can be recycled to produce more ATP with the energy produced from food in animals or photosynthesis in plants.
It also has medical uses. When injected into the bloodstream, it slows the heart rate due to its electrical effects on the atrioventricular node, which regulates heartbeat, and inhibit the release of the neurotransmitter norepinephrine. It also causes the smooth muscle tissue around arteries to relax and dilate. Adenosine is used by doctors to identify artery blockages or abnormalities in heartbeat. It can also be an effective treatment for some cases of abnormally accelerated heartbeat, or tachycardia.