Which energy-carrying molecule is produced by mitochondria during cellular respiration?

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

Answer: (B)

Mitochondria turn the energy from nutrients into ATP, the cell’s main energy currency. In the mitochondrial inner membrane, electrons move through the electron transport chain, creating a proton gradient. That gradient powers ATP synthase to combine ADP with inorganic phosphate, forming ATP. This ATP is the immediate energy source the cell uses for work like muscle contraction and active transport. NADH plays a supporting role by carrying high-energy electrons to the chain to help drive the gradient, but it isn’t the final energy carrier produced. Glucose is the fuel that gets broken down earlier, and ADP is the substrate that ATP is made from. So ATP is the energy-carrying molecule produced by mitochondria during cellular respiration.