Final answer:
ATP is crucial in cellular metabolism as it serves as an energy shuttle between exergonic and endergonic reactions, facilitating energy transfer through the process of phosphorylation, which is central to the function of living cells.
Step-by-step explanation:
The Critical Role of ATP in Cellular Metabolism
Adenosine triphosphate (ATP) plays a pivotal role in cellular metabolism functioning as the primary energy-supplying molecule for living cells. It consists of a nucleotide, a five-carbon sugar, and three phosphate groups. The high-energy phosphoanhydride bonds between the phosphates are key to ATP's role in energy transfer within the cell.
ATP is critically involved in powering both exergonic and endergonic reactions. During ATP hydrolysis, ATP is converted into ADP and Pi (inorganic phosphate), releasing energy that is utilized for cellular work, such as muscle contraction or active transport. The coupling of ATP hydrolysis with endergonic reactions is essential as it allows for energy transfer through phosphorylation, where ATP donates its phosphate group to another molecule, making it less stable and more reactive, thus enabling the molecule to participate in further chemical reactions.
The statement that best describes ATP’s critical role is: ATP serves as an energy shuttle in the cell, coupling exergonic and endergonic reactions (A). This is because ATP functions as an energy carrier, allowing for the transfer of energy from reactions that release energy (exergonic) to those that require energy (endergonic), thereby driving a wide variety of biological processes.