What is ATP?
ATP stands for adenosine triphosphate. It is an organic chemical that is used as the basic unit of energy fuel for cells. All living organisms, including prokaryotes, use ATP. Without ATP, cells would not be able to transfer energy from one location to another and complex life as we know it would not be possible.
When cells generate energy from food (in the case of animals and fungi) or light (in the case of plants), it is captured and stored as ATP. Later, when cells require energy to move, reproduce, synthesize proteins, or perform any other cellular process, they break down ATP to release the energy it holds in its bonds.
ATP Molecule: ImageSource - FreeCliparts (2011)
A more concrete and visible example of ATP in action can be seen in the abdomen of a firefly on a warm summer night. To create their characteristic glow, fireflies mix ATP with a unique enzyme called luciferase. The resulting chemical reaction uses the energy stored in ATP to generate light.
Cells synthesize ATP in their mitochondria through a chemical reaction known as “cellular respiration”. The usual inputs for cellular respiration are glucose and oxygen, and the outputs are water, carbon dioxide (a waste product that we then exhale), and readily usable energy in the form of ATP. The human body prefers to burn carbohydrates to generate ATP, but it can also use lipids if no carbohydrates are available.
Some scientists refer to ATP as the “molecular unit of currency”, because it is used for energy transfer in literally all forms of life. The human body is constantly generating and breaking down ATP (into either adenosine diphosphate or adenosine monophosphate), to the point that we recycle our own body weight in ATP every single day!
FreeCliparts (artist). (2011). Molecule Nucleotide ATP [digital art]. Retrieved from