explain the membrane system in mitochondria

# Mitochondria are surrounded by a double-membrane system, consisting of inner and outer mitochondrial membranes separated by an intermembrane space The inner membrane forms numerous folds (cristae), which extend into the interior (or?matrix) of the organelle. Each of these components plays distinct functional roles, with the matrix?and inner membrane representing the major working compartments of mitochondria.
# In contrast to the inner membrane, the outer mitochondrial membrane is freely permeable to small molecules. This is because it contains proteins called porins which form channels that allow the free diffusion of molecules smaller than about 6000 daltons. The composition of the intermembrane space is therefore similar to the cytosol with respect to ions and small molecules.
# Consequently, the inner mitochondrial membrane is the functional barrier to the passage of small molecules between the cytosol and the matrix and maintains the proton gradient that drives oxidative phosphorylation.
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