What is the purpose of the outer mitochondrial membrane?

Question

The purpose of mitochondria is to generate ATP, utilising a chemiosmotic gradient across the inner mitochondrial membrane. Protons are pumped out of the mitochondria into the intermembrane space, but because the outer mitochondrial membrane is highly permeable to ions, the pH of the intermembrane space quickly equilibrates with the rest of the cell. As the outer membrane apparently does not contribute to maintaining this chemiosmotic gradient, what is its purpose? It seems to be doubly redundant in chloroplasts as H+ transport doesn't even occur across the inner membrane.

Answer 1

The outer membrane is a phospholipid bilayer. It is selectively permeable to small, nonpolar ions such as CO2, O2, It is not permeable to hydrogen ions and serves a second outer barrier together with the inner membrane to form the intermembrane space. Like all membranes it has protein channels for transport of larger and polar molecules. It also serves to protect the inside of the organelle from the cytoplasmic contents. It also contains proteins for recognition (to avoid attack by the immune system.) And remember mitiochondria were once bacteria (endosymbiotic theory.) Bacteria have two "membranes" or cell membrane and cell wall.