Adenosine triphosphate (ATP) is widely present in animals, plants, microorganisms, and cultured cells. It functions as a coenzyme that facilitates metabolism and participates in the metabolism of fats, proteins, carbohydrates, nucleic acids, and nucleotides. ATP serves as a primary energy source for biological processes. Cellular energy charge is a key indicator of cellular metabolic status. Measuring ATP content and calculating energy charge provides a direct assessment of energy metabolism.