What is the mitochondrion and its primary function?

• A. An organelle whose primary function is to generate ATP via oxidative phosphorylation
• B. A ribosome; protein synthesis
• C. A nucleus; genetic storage
• D. A lysosome; degradation of cellular waste

Answer: (A)

The mitochondrion is the cell’s energy-producing organelle, and its main job is to generate ATP, the cell’s usable energy, through oxidative phosphorylation. This process occurs in the inner mitochondrial membrane, where the electron transport chain passes electrons and pumps protons to create a gradient. ATP synthase then uses that proton flow to convert ADP and inorganic phosphate into ATP. The TCA cycle in the mitochondrial matrix feeds electrons into the chain, sustaining the energy production. Mitochondria also have roles in regulating metabolism and apoptosis, but their core function remains rapid, efficient ATP generation.

Ribosomes, by contrast, are the sites of protein synthesis; the nucleus stores genetic material; and lysosomes break down cellular waste.