Mitochondria are enclosed by a double-membrane system made up of an inner and an outer membrane. The space between these two membranes is called (surprise!) the intermembrane space. The inner membrane encloses the interior of the mitochondrion, which is known as the mitochondrial matrix.The inner membrane also forms a large number of folds, called cristae, that extend into the matrix.See Fig.he space between these two membranes is called (surprise!) the intermembrane space. The inner membrane encloses the interior of the mitochondrion, which is known as the mitochondrial matrix. The inner membrane also forms a large number of folds, called cristae, that extend into the matrix. See Fig.
1 The strict definition of relative atomic mass (Ar) is that it equals the average mass of all the isotopic atoms present in the element compared to 1/12th the mass of a carbon-12 atom (relative isotopic mass of 12.0000).
Atomic mass is the total mass of protons and neutrons in an individual atom or isotope. Atomic weight is the average mass of all of the naturally-occurring isotopes of an element. Both atomic mass and atomic weight are represented using a unit called the atomic mass unit (amu), which was defined using carbon's most common isotope, carbon-12.