Which organelle houses the electron transport chain essential for oxidative phosphorylation?

• A. Nucleus
• B. Golgi apparatus
• C. Mitochondria
• D. Endoplasmic reticulum

Answer: (C)

The organelle where the electron transport chain energizes oxidative phosphorylation is the mitochondrion. The ETC sits in the inner mitochondrial membrane, where electrons are passed along a series of protein complexes. This transfer pumps protons across the membrane, creating a proton gradient that powers ATP synthase to convert ADP and inorganic phosphate into ATP. The other organelles mentioned don’t host the ETC: the nucleus stores genetic material, the Golgi apparatus processes and packages proteins, and the endoplasmic reticulum handles lipid synthesis and protein folding. So, mitochondria are the site of the electron transport chain and oxidative phosphorylation.