Which molecule is primarily responsible for transporting energy within a cell?

ATP, or adenosine triphosphate, is the primary molecule responsible for transporting energy within a cell. It acts as the main energy currency of the cell, providing a readily available source of energy for various cellular processes. When ATP is hydrolyzed, it releases energy through the breaking of high-energy phosphate bonds, which cells then harness to fuel activities such as muscle contraction, protein synthesis, and cellular signaling.

Unlike lipids, which serve more structural and storage functions, ATP specifically delivers energy for immediate use. RNA plays a critical role in the synthesis of proteins but does not primarily function in energy transport. Proteins perform a wide range of functions, including catalyzing reactions and providing structural support, but they do not serve as the main energy carriers like ATP. Therefore, ATP stands out as the essential molecule directly involved in the energy transport mechanism within cells.