The outer membrane separates the mitochondrion from cytoplasm,
realizes the inclusion of different substances by means of transport proteins
forming hydrophilic channels in the lipid double layer and is pervious to the
products of metabolic processes running in the matrix. It contains enzymes
performing different functions.
The inner membrane forms a number of folds in the mitochondrion
interior, which increase its total surface. It is more impermeable, compared
to the outer membrane. It contains proteins catalyzing oxidative reactions of
respiratory chain, an enzymatic complex called ATP-synthetase and
specific transport protein molecules realizing the transfer of metabolites in
the matrix and outside of it.
The distance between outer and inner membrane is called
intermembrane space. A number of enzymes are there. Mainly they
perform transport functions.
The matrix represents a mixture of different substances and high-
molecular compounds. It fills the interior of mitochondrion. In it there are
carried out most biochemical processes related with the functions of this
organelle. It contains a rich set of different enzymes, including acetyl-CoA
necessary for the inclusion in the Crebs cycle. The end products of this
complex biochemical cycle are CO₂ and H₂O, with forming NAD.H and
PAD.H₂. Carbon dioxide comes off outside, and NAD.H and PAD.H₂ serve
as main sources of electrons in their transfer along the respiratory chain
and by forming H⁺ ₂O from H and O⁻. The released energy is used in the
synthesis of ATP. In the matrix there are also located specific DNA, RNA
and ribosomes, become known as mitochondrial.
For a long time the structural organization and diverse vital important
functions of mitochondria in the cells attract the attention of investigators. The
interest in them is great also from genetic point of view. It was established that
they possess a certain autonomy and can divide independently (Fig. 2–66).
image
Figure 2–66. Division of mitochondrion in a cell of rat liver (Courtesy of D. Friend; From Fawcett, 1981).