ATP

Adenosine triphosphate is a nucleotide that cells use to transfer chemical energy and phosphate groups. Its binding and hydrolysis power cellular work, including myosin cycling.

ATP hydrolysis: The reaction that cleaves ATP’s terminal phosphate bond, producing ADP, inorganic phosphate, and usable free energy. Myosin’s ATPase reaction helps reset the motor head and supports its movement along actin.
Adenosine: A nucleoside composed of adenine joined to ribose. Adenosine forms the molecular core shared by ATP, ADP, and AMP.
Muscle contraction: The generation of force by muscle fibers through interactions between actin and myosin. ATP enables myosin detachment and reactivation during repeated force-producing cycles.
Guanosine triphosphate: A nucleotide that supplies energy and phosphate groups in processes including protein synthesis and signaling. GTP can power cellular reactions, but myosin cycling specifically uses ATP.
Oxidative phosphorylation: The mitochondrial process that uses electron transport and a proton gradient to produce ATP. It supplies much of the ATP used by sustained cellular activity.
Myosin: A family of motor proteins that use ATP hydrolysis to move along actin filaments or generate tension. ATP binding and hydrolysis change myosin’s interactions with actin during each cycle.
Nucleotide: A molecule made of a nitrogenous base, a five-carbon sugar, and one or more phosphate groups. ATP is a nucleotide whose three phosphates distinguish it from nucleosides.
Active transport: The movement of substances across membranes against a gradient using energy from ATP or another source. ATP directly powers pumps that maintain essential concentration gradients.
Creatine phosphate: A high-energy phosphate reserve that rapidly transfers phosphate to ADP in vertebrate muscle. It buffers ATP supply during sudden muscular demand rather than powering myosin directly.
Glycolysis: A pathway that breaks down glucose into pyruvate while generating ATP and reducing equivalents. It can produce ATP rapidly, including when oxygen-dependent metabolism is limited.

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