What molecule supplies the cell with usable energy currency in most cellular processes?

• A. NADH
• B. ATP
• C. FADH2
• D. GTP

Answer: (B)

ATP serves as the universal energy currency in the cell. The energy stored in its terminal phosphate bond is readily released by hydrolysis and used to drive countless cellular tasks, from muscle contraction to transport across membranes and the operation of enzymes and motor proteins. This phosphorylation capability lets many reactions proceed by supplying the needed energy and also allows rapid regulation of metabolic pathways. While NADH and FADH2 carry energy in the form of high-energy electrons to the electron transport chain to generate ATP, they are not directly used to power most reactions. GTP provides energy in certain specific steps, such as some aspects of protein synthesis and signaling, but ATP is the most broadly utilized energy source across cellular processes.