The energy-carrying molecule that powers muscle contraction, abbreviated ATP, stands for what?

The energy-carrying molecule abbreviated ATP stands for adenosine triphosphate. It is a nucleotide-like molecule made from the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate groups. Cells use ATP to transfer energy to processes that require it, including muscle contraction.

During contraction, ATP binds to the motor protein myosin. Enzymatic breakdown of ATP to ADP and inorganic phosphate changes the position of the myosin head, enabling it to bind to actin and produce a power stroke. A new ATP molecule then allows myosin to detach from actin, so the cycle can repeat. ATP is also needed to help pump calcium back into storage after contraction.

ATP is often called the cell’s energy currency, but it is not a permanent energy store. Cells continually regenerate it from ADP through pathways including glycolysis, the citric acid cycle, and oxidative phosphorylation. ADP means adenosine diphosphate, with two phosphate groups; AMP means adenosine monophosphate, with one. Those related molecules are common mix-ups, but only the three-phosphate form is ATP.