Which statement best describes mitochondrial energy transformation?

• A. They transform the energy that was in the bonds of food into ATP
• B. They transform ATP into chemical energy
• C. They store pigments
• D. They synthesize proteins

Answer: (A)

Mitochondria transform chemical energy stored in food into ATP, the cell’s usable energy currency. In cellular respiration, energy locked in the chemical bonds of nutrients like glucose is harvested through a series of steps. High-energy electrons are carried by NADH and FADH2 to the inner mitochondrial membrane, where the electron transport chain uses that energy to pump protons and create a gradient. ATP synthase then uses this gradient to convert ADP and inorganic phosphate into ATP. This is the core way cells convert the energy from food into a form that powers most cellular activities. The other choices describe actions that aren’t the main energy transformation in mitochondria: ATP isn’t converted back into chemical energy by mitochondria, pigments aren’t stored there, and while mitochondria make a few proteins, that isn’t the process that generates usable energy.