Final answer:
ATP, or Adenosine triphosphate, is a molecule used by cells to store and transfer energy. It contains high energy bonds between its second and third phosphate groups, known as phosphoanhydride bonds, which release energy when hydrolyzed.
Step-by-step explanation:
Adenosine triphosphate (ATP) is a molecule that serves as the primary energy-supplying molecule for living cells. ATP consists of an adenine base, a ribose sugar, and three phosphate groups. The bonds between these phosphate groups, specifically the bonds between the second and third phosphate (also known as phosphoanhydride bonds), are considered high-energy due to the considerable amount of potential energy they store. When these high-energy bonds are broken through a process called hydrolysis, a significant amount of energy is released. This energy is harnessed to perform various cellular functions, such as muscle contraction, transport of substances across cell membranes, and driving endergonic (energy-requiring) chemical reactions. The last two of these phosphate bonds are particularly high-energy, with the hydrolysis of each yielding around 7.4 kcal/mol. These two bonds are known as the phosphate bonds, whereas the first bond (the bond connecting the first phosphate group to the ribose sugar) releases only 4 kcal/mol when hydrolyzed, thus is not considered a high-energy bond.