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Simplified structure of mitochondrion

The intermembrane space of a Mitochondrion refers to the compartment formed between the inner and outer mitochondrial membranes.[1]

The intermembrane space is chemically similar to cytosol, but includes a large amount of small proteins as well. As electrons move down the proteins in the electron transport chain, the electrons lose energy to bring H+ ions from the mitochondrial matrix into the intermembrane space. As a concentration gradient of hydrogen ions forms, a protein called ATP synthase harnesses the potential energy of these ions and starts chemiosmosis, where the H+ ions reenter the matrix via this enzyme bound to the cristae (folds of the inner membrane). ADP and a phosphate group are combined to form ATP.


  1. ^ Alberts, B; Johnson, A; et al. (2002). Molecular Biology of the Cell. 4th edition. Garland Science.