In cell biology, a mitochondrion plural mitochondria is an organelle, variants of which are found in

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In cell biology, a mitochondrion plural
mitochondria is an organelle, variants of which
are found in most eukaryotic cells. Mitochondria
are sometimes describes as being cellular power
plants because of their ability to convert
organic materials into energy in the form of ATP
adenosine triphosphate via the process of
oxidative phosphorylation the terminal process
of cellular respiration in eukaryotes. Usually a
typical cell has hundreds or thousands of
mitochondria, depending on the cells energy
demands, which can occupy up to 25 of the cells
cytoplasm. Mitochondria are present in all plant
and animal cells. Using suitable staining
techniques, they are just visible through a light
microscope, appearing as tiny rods in the
cytoplasm, varying from about 1.5 to 10µm in
length, with a fixed diameter of about 1 µm.
Their main function is to provide the release of
energy during aerobic respiration and manufacture
a source of chemical energy ATP which can be
used in the cell to drive its metabolism.
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A mitochondrion contains outer and inner
membranes composed of phospholipid bilayers and
proteins. Because of this double membraned
organisation, there a five distinct compartments
within mitochondria. There is the outer membrane,
the intermembrane space the space between the
outer and inner membranes, the inner membrane,
the cristae space formed by infoldings of the
inner membrane and the matrix space within the
inner membrane.
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Energy Conversion A dominant role for the
mitochondria is the production of ATP as
reflected by the large number of proteins in the
inner membrane for this task. This is done by
oxidising the major products of glycolysis
pryuyate and NADH that are produced in the
cytosol. This process of cellular respiration,
also known as aerobic respiration, is dependent
on the presence of oxygen. When oxygen is limited
the glycolytic products will be metabolised by
anaerobic respiration a process that is
independent of the mitochondria. The production
of ATP from glucose has an approximately 15 fold
higher yield during aerobic respiration compared
to anaerobic respiration.

• Although it is well known that the mitochondria
  convert organic materials into cellular energy in
  the form of ATP, mitochondria play an important
  role in many metabolic tasks, such as
• Apoptosis - programmed cell death
• Glutamate - mediated excitotoxic neuronal injury
  
• Cellular proliferation
• Regulation of the cellular redox state
• Heme synthesis
• Steroid synthesis
• Some mitochondrial functions are performed only
  in specific types of cells. For example,
  mitochondria in liver cells contain enzymes that
  allow them to detoxify ammonia, a waste product
  of protein metabolism. A mutation in the genes
  regulating any of these functions can result in
  mitochondrial diseases.

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