Mitochondrion structure

Mitochondrion (plural:mitochondria) is the "power plant" of the cell. Here cellular respiration occurs and most of the high energy ATP molecules are produced. Scientists believe that mitochondria originate from early prokaryotes that entered early primitive eucaryotic cells and established symbiosis with them.

Mitochondrion has a double membrane. The outer membrane, believed to be of the cellular origin, is more permeable and the inner membrane which might belong to the early prokaryote, is less permeable and here the enzymes of the cellular respiration occur.