What is the primary function of mitochondria in a cell?

• A. Produce energy (ATP) for the cell
• B. Store genetic material
• C. Synthesize proteins
• D. Digest waste

Answer: (A)

Energy production is the main job of mitochondria. They convert nutrients into ATP, the cell’s energy currency, to power all cellular activities. This happens through cellular respiration: glycolysis in the cytoplasm breaks glucose into smaller units, these units enter the mitochondria to feed the TCA cycle, and the electrons carried by NADH and FADH2 move through the electron transport chain. The resulting proton gradient drives ATP synthase to make ATP from ADP and phosphate, with oxygen acting as the final electron acceptor. While mitochondria do contain some of their own DNA and ribosomes and can produce a few proteins, their primary role is generating energy. Other functions listed—storing most genetic material (that’s mainly in the nucleus), synthesizing proteins (primarily by ribosomes in the cytosol and rough ER), and digesting waste (handled by lysosomes)—are handled by other parts of the cell.