The Importance of Mitochondria

All metabolic processes require an ongoing source of energy.  Oxygen evolved as
the energy source for most complex life forms as it increased to about 20 percent of
the earth’s atmosphere over 2.5 billion years ago [1].  Other chemical components
of the primordial world (sulfate, nitrate, metal ions, and methane) provided energy
for the evolution of metabolism in the earliest life forms [2, 3].  Many of these
organisms still exist and produce oxygen to maintain its level (at 20.95%) in
equilibrium with nitrogen (at 78.08%) plus water vapor, argon, carbon dioxide, and
trace amounts of other gases [4].  As in many other areas of human endeavor it
may not be smart to develop industrial process that tamper with and could abruptly
change the natural equilibrium of these components that have evolved over so
many eons.

Aerobic organisms are dependent upon a continuing supply of oxygen.  For most
aerobic species evolution has only provided capability for short-term storage of
oxygen, via compex molecules like hemoglobin, myoglobin, and neuroglobin [5-7].  
As is well known oxygen can combine with other elements in an explosive way.  Thus
electrons from atmospheric oxygen are taken as the last step of a controlled
sequence of “respiratory chain” reactions [8].  The enzymes that control this series
of reactions are found in intracellular organelles known as mitochondria [9, 10].

That respiration (and life) depended upon oxygen was understood by its
discoverers in the late 18th century [11, 12].  However, as recently pointed out by
Scheffler:

    “Lavoisier was correct in viewing respiration as a combustion, but little did
    he suspect of the many steps necessary to make this “burning” of glucose
    in a living cell such a controlled process.” [10, p251]

Oxygen is not stored in tissues except for short periods of time [6, 7].  Intake (via the
lungs in mammals) is an urgent ongoing need.  The placenta serves this function for
the developing mammalian fetus.  Erasmus Darwin (grandfather of Charles Darwin)
pointed out in 1796:

    "The placenta is an organ for the purpose of giving due oxygenation to the
    blood of the fetus; which is more necessary, or at least more frequently
    necessary, than even the supply of food." [13, p350]

Oxygenated blood from the lungs or placenta is delivered to the heart for circulation
throughout the body.  Oxygen does not just circulate freely in the blood stream.  It is
bound to hemoglobin, which is sequestered in the red blood cells.  Hemoglobin
releases oxygen to body tissues only in exchange for the metabolic end-product
carbon dioxide generated by the metabolic activity of each organ.  The controlled
delivery of oxygen in exchange for carbon dioxide is known as the Bohr Effect of
hemoglobin [14].

Metabolic activity is not uniform throughout the body.  Muscles have higher
metabolic needs during exercise, and in the brain nuclei in the auditory system have
the highest metabolic need [15].  The auditory system appears to be the alerting
system of the brain and is continuously active even during sleep [16].

Mitochondria are bacteria-like.  They may have originated as an infection that
proved symbiotic in conferring the ability to use oxygen to produce energy for
myriad metabolic processes in host organisms [17, 18].  Mitochondria are sensitive
to antibacterial and other chemical substances [19-21].  Antibiotics were in use for
barely a decade when the discovery was made that they could cause brain damage
in premature infants [22, 23].  

Autism is associated with mitochondrial disorders [24].  Some of these may have
been drug induced directly in early childhood, or due to medications and
substances used by the mother even before pregnancy.  Mitochondrial disorders,
and maternal drug use, should be looked for in every case of two or more siblings
with autism.

References
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  3. Wikipedia. Obligate Anaerobe. http://en.wikipedia.
    org/wiki/Obligate_anaerobe  (accessed 12 September 2009)
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    September 2009)
  5. Wikipedia. Hemoglobin. http://en.wikipedia.org/wiki/Hemoglobin (accessed 12
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  6. Wikipedia. Myoglobin. http://en.wikipedia.org/wiki/Myoglobin (accessed 12
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