Which organelle is known as the powerhouse of the cell, producing ATP?

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

Answer: (B)

The main idea here is energy production in the cell. Most ATP—the cell’s energy currency—is made in the mitochondria during cellular respiration. Glucose and other fuels are broken down in stages, and the energy released is captured by electron carriers that feed the electron transport chain. As electrons move through this chain, a protein complex called ATP synthase uses that flow of energy to synthesize ATP. That’s why mitochondria are nicknamed the powerhouse of the cell.

Ribosomes, by contrast, are the protein factories of the cell. Chloroplasts (in plants and algae) capture light energy to drive photosynthesis, producing sugars and some ATP, but only in photosynthetic organisms. Peroxisomes help break down fatty acids and detoxify certain molecules. In many cells, the mitochondria are the main ATP producers, which is why they’re considered the cell’s energy powerhouse.