How is kinetic energy released in cells from organic molecules?

• A. By absorbing energy from sunlight
• B. By storing energy as chemical potential energy
• C. By breaking bonds during cellular respiration and fermentation, releasing energy as kinetic energy
• D. Outside the cell, burning fuel

Answer: (C)

Energy stored in the bonds of organic molecules is released when those bonds are broken during cellular respiration and fermentation. As these bonds break, energy becomes available and is primarily captured to form ATP, which the cell uses for work. At the same time, some of that energy is released as heat, increasing the kinetic energy of molecules inside and around the cell. This is the form of energy we associate with metabolic heat production.

Absorbing sunlight powers photosynthesis, not the breakdown of organic matter for energy in cells. Burning fuel outside the cell is combustion, not cellular metabolism, so it doesn’t describe how cells release energy.