Which organelle is known as the powerhouse of the cell?

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

Answer: (A)

Mitochondria generate most of the cell’s ATP, the energy currency the cell uses to power its activities. They do this through cellular respiration, where chemical energy from nutrients is captured in the inner-membrane processes of the Krebs cycle and, especially, the electron transport chain. As electrons are transferred along the chain, a proton gradient is created across the membrane, and ATP synthase uses that gradient to produce ATP. This energy-producing role is why mitochondria are called the powerhouse of the cell. They also carry their own DNA and ribosomes, underscoring their specialized, energy-focused function. In contrast, the nucleus stores genetic material, ribosomes are the sites of protein synthesis, and the Golgi apparatus packages and ships molecules—none of which directly generate ATP on a large scale.