Final answer:
ATP is produced primarily through oxidative phosphorylation during glucose catabolism and in the citric acid cycle, as well as through substrate-level phosphorylation involving various enzymatic reactions. ATP is known as the primary energy currency of cells, driving many cellular activities.
Step-by-step explanation:
The ATP-producing reactions include oxidative phosphorylation and substrate-level phosphorylation. Oxidative phosphorylation occurs as part of the process known as chemiosmosis, which generates about 90% of the ATP during glucose catabolism. This process takes place in the mitochondria of eukaryotic cells and the plasma membrane of prokaryotic cells. Another crucial reaction that contributes to ATP production is seen in the citric acid cycle, where the oxidation of molecules is coupled with the phosphorylation of ADP to form ATP.
The other reactions that involve ATP production include the reversible transfer of a phosphate group from ATP to a protein in phosphorylation, and the reaction catalyzed by phosphoglycerate kinase, which yields ATP from ADP and inorganic phosphate (Pi).
Cells harness energy through a concept called energy coupling, using exergonic reactions like the hydrolysis of ATP to drive endergonic reactions required for cellular activity. Therefore, ATP is integral as a primary energy currency for powering cellular reactions, representing an essential aspect of cellular respiration and metabolism.