Which organelle is known as the powerhouse of the cell?

• A. Nucleus
• B. Ribosome
• C. Mitochondrion
• D. Chloroplast

Answer: (A)

The organelle responsible for powering the cell is the mitochondrion, where most ATP—the cell’s energy currency—is produced through cellular respiration. In this process, glucose is broken down and energy is captured to form ATP, with the majority generated during oxidative phosphorylation on the inner membrane’s electron transport chain. The inner membrane folds into cristae, boosting surface area and making the production of ATP more efficient. This energy fuels virtually every cellular activity, from muscle contraction to transporting substances across membranes and running chemical reactions.

For context, the nucleus houses genetic material and directs cell activities; ribosomes synthesize proteins; and chloroplasts (in plants and some algae) convert light energy into chemical energy during photosynthesis. Because ATP production happens primarily in mitochondria, they’re known as the powerhouse of the cell.