  The inner mitochondrial membrane has been shown to have a novel structure
that contains tubular components whose radii are on the order of 10 nm as well
as comparatively flat regions. The structural organization of mitochondria is
important to understanding their functionality. We present a model that can
account, thermodynamically, for the observed size of the tubules. The model
contains two lipid constituents with different shapes. They are allowed to
distribute in such a way that the composition differs on the two sides of the
tubular membrane. Our calculations make two predictions: (1) there is a
pressure difference of 0.2 atmospheres across the inner membrane as a necessary
consequence of the experimentally observed tubule radius of 10 nm. and (2)
migration of differently shaped lipids causes concentration variations between
the two sides of the tubular membrane on the order of 7 percent.
