ATP serves as a vital energy carrier in cells, facilitating the transfer of energy from exergonic reactions to endergonic reactions.

Adenosine triphosphate (ATP) is a key molecule that both stores and transfers energy within cells. It consists of three main components: a nitrogenous base known as adenine, a sugar called ribose, and three phosphate groups. The bonds connecting these phosphate groups are high-energy bonds, which, when broken, release energy.

When cells require energy for various processes, ATP donates one of its phosphate groups to another molecule, such as a protein or enzyme, in a process known as phosphorylation. This transfer of a phosphate group releases energy that can be harnessed to drive endergonic reactions, including muscle contraction and protein synthesis.

Following the donation of a phosphate group, ATP is converted to adenosine diphosphate (ADP), which contains only two phosphate groups. The ADP can be recycled back into ATP through cellular respiration, a process that breaks down glucose and other substrates to release energy, enabling the reformation of ATP.

In summary, ATP plays a crucial role as an energy carrier in cellular functions by transferring energy from exergonic reactions to endergonic reactions through the donation of phosphate groups. Its ability to be recycled and reused makes it an essential molecule for sustaining various cellular processes.