Which organelle generates ATP through cellular respiration?

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

Answer: (D)

The organelle responsible for generating most of the ATP during cellular respiration is the mitochondrion. Cellular respiration uses glucose broken down in steps that occur in different parts of the cell, but the main ATP production happens inside the mitochondria. Here, pyruvate from glycolysis is further processed to produce electron carriers, the citric acid cycle runs to release energy, and the electron transport chain uses that energy to pump protons across the inner mitochondrial membrane. The flow of protons back through ATP synthase drives the synthesis of ATP from ADP. Oxygen acts as the final electron acceptor, making this aerobic respiration. Other organelles have different roles—nuclei house genetic material, ribosomes build proteins, and chloroplasts in plants generate ATP through photosynthesis rather than respiration—so the mitochondria are the site where ATP is produced via cellular respiration.