Journal of Energy Bioscience 2025, Vol.16, No.1, 21-30 http://bioscipublisher.com/index.php/jeb 24 4 The Role of ATP in Cellular Processes 4.1 The role of ATP in cellular respiration and energy transfer ATP plays a crucial role in cellular respiration and energy transfer, particularly in the oxidative phosphorylation process of mitochondria within cells. In mitochondria, there are five enzyme complexes and two electron donating molecules that combine the energy generated from oxidation reactions to synthesize ATP. During this process, a proton gradient is formed, which is the main pathway for cells to obtain energy. In order to prevent respiratory chain problems from causing diseases, the entire process has strict regulatory mechanisms (Kadenbach, 2020; Vercellino and Sazanov, 2021). A protein called adenine nucleotide transporter (ANT) allows ADP and ATP to cross mitochondrial membranes (Atlante and Valenti, 2021). 4.2 ATP as a substrate for phosphorylation reaction Phosphorylation reactions are crucial for many intracellular activities. F-type ATP synthase can convert ADP into ATP, and this process provides energy through the electrochemical gradient on the membrane. The concentration of ADP and ATP regulates this reaction, maintaining the energy balance within the cell (Turina, 2022). ATP can also reversibly phosphorylate cytochrome c oxidase (COX), regulate the rate of oxidative phosphorylation, and reduce the production of reactive oxygen species (Kadenbach, 2020). 4.3 The role of ATP in active transport and ion channels ATP also participates in the active transport of ions on the cell membrane, which is important for maintaining ion balance inside and outside the cell. By hydrolyzing ATP, ATPase can provide energy and help Na+, K+, and Ca2+ions cross the cell membrane, which is crucial for neural signal transduction and muscle activity (Ji et al., 2021). There is also a type of structure called ABC transporters, which utilize the energy generated by ATP breakdown to transport toxins and nutrients into or out of cells (Rigoulet al., 2020). 4.4 The role of ATP in muscle contraction and cytoskeletal dynamics ATP is also very important in muscle contraction and cytoskeletal activity. During muscle contraction, ATP binds to the myosin head, helping it separate from actin filaments and prepare for the next contraction cycle (Figure 2). This process occurs repeatedly in the cross-linking cycle and is the basis for muscle contraction and movement (Alghannam et al., 2021). ATP is also crucial for the polymerization and depolymerization of actin filaments, which are the main part of the cytoskeleton, maintaining cell morphology and movement, and participating in processes such as cell division (White and Yang, 2022). Figure 2 Simplified overview illustrating the major fuel sources supporting endurance-type exercise. ATP, adenosine triphosphate; PCr, phosphocreatine; IMTG, intramyocellular triacylglycerol (Adopted from Alghannam et al., 2021)
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