Why does mitochondria have two membranes and how does this unique structure contribute to its function within the cell?

Mitochondria have two membranes because they are believed to have originated from a symbiotic relationship between a primitive eukaryotic cell and a prokaryotic cell. The outer membrane helps protect the organelle, while the inner membrane contains proteins essential for energy production through cellular respiration. This unique structure allows mitochondria to generate ATP, the cell's main energy source, through the process of oxidative phosphorylation.