Which organelle is described as the cell's 'powerhouse' because it generates ATP?

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

Answer: (A)

Mitochondria are the cell's powerhouse because they generate most of the ATP that fuels cellular activities through cellular respiration. Energy from nutrients is processed first by glycolysis in the cytosol, and the resulting molecules enter the mitochondria to power the citric acid cycle and the electron transport chain, which together produce ATP via oxidative phosphorylation. The inner membrane folds, called cristae, increase surface area, allowing more electron transport chains to operate and boosting ATP yield. The mitochondrial matrix houses enzymes for the citric acid cycle, and mitochondria even contain their own DNA and ribosomes, reflecting their evolutionary origin. By contrast, the nucleus stores genetic information and directs cell activities; ribosomes synthesize proteins; the Golgi apparatus modifies and ships proteins—none of these primarily generate ATP.