During cellular respiration, the primary energy currency produced is what?

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

Answer: (D)

ATP is the molecule cells use as their immediate energy currency. In cellular respiration, glucose is gradually broken down through glycolysis, the citric acid cycle, and oxidative phosphorylation. The energy from glucose is captured first in high-energy electron carriers, NADH and FADH2, which deliver electrons to the electron transport chain. As these electrons move through the chain, their energy pumps protons across a membrane, creating a gradient. ATP synthase uses that proton-motive force to convert ADP and inorganic phosphate into ATP. So the energy ultimately stored and used for cellular work is in ATP, while NADH and FADH2 are carriers that help generate it. Glucose is the fuel that starts the process, not the immediate energy currency.