Which organelle is the powerhouse of the cell?

• A. Mitochondrion
• B. Nucleus
• C. Ribosome
• D. Golgi apparatus

Answer: (A)

Energy production in cells hinges on mitochondria. They host the main steps of cellular respiration—Glycolysis happens in the cytosol, but the majority of ATP comes from the Krebs cycle and the electron transport chain inside the mitochondria. As electrons move through the chain, a proton gradient drives the synthesis of ATP from adenosine diphosphate (ADP). The inner membrane’s folds, called cristae, increase surface area to maximize this energy production.

Mitochondria also contain their own DNA and ribosomes, reflecting their semi-autonomous nature, and they can influence programmed cell death when needed. In contrast, the nucleus stores genetic material and directs cellular activities, ribosomes build proteins, and the Golgi apparatus processes and ships those proteins. Because mitochondria generate most of the cell’s usable energy, they’re best described as the powerhouse of the cell.