Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

756 Chapter 14: Energy Conversion: Mitochondria and Chloroplasts
(A)
(B)
10 µm
fission, which, as we discuss later, is involved in the distribution and partitioning
of mitochondria within cells (Figure 14–7).
The acquisition of mitochondria was a prerequisite for the evolution of complex
animals. Without mitochondria, present-day animal cells would have had to
generate all of their ATP through anaerobic glycolysis. When glycolysis converts
glucose to pyruvate, it releases only a small fraction of the total free energy that
is potentially available from glucose oxidation (see Chapter 2). In mitochondria,
the metabolism of sugars is complete: pyruvate is imported into the mitochondrion
and ultimately oxidized by O 2 to CO 2 and H 2 O, which allows 15 times more
ATP to be made from a sugar than by glycolysis alone. As explained later, this
became possible only when enough molecular oxygen accumulated in the Earth’s
atmosphere to allow organisms to take full advantage, via respiration, of the large
amounts of energy potentially available from the oxidation of organic compounds.
Mitochondria are large enough to be seen in the light microscope, and they
were first identified in the nineteenth century. MBoC6 Real m14.05/14.05
progress in understanding
their internal structure and function, however, depended on biochemical procedures
developed in 1948 for isolating intact mitochondria, and on electron
microscopy, which was first used to look at cells at about the same time.
Figure 14–5 The relationship between
mitochondria and microtubules. (A) A
light micrograph of chains of elongated
mitochondria in a living mammalian
cell in culture. The cell was stained
with a fluorescent dye (rhodamine 123)
that specifically labels mitochondria in
living cells. (B) An immunofluorescence
micrograph of the same cell stained
(after fixation) with fluorescent antibodies
that bind to microtubules. Note that the
mitochondria tend to be aligned along
microtubules. (Courtesy of Lan Bo Chen.)
mitochondria
flagellar axoneme
myofibril of contractile apparatus
(A)
CARDIAC MUSCLE
(B) SPERM TAIL
Figure 14–6 Localization of mitochondria near sites of high ATP demand in cardiac muscle
and a sperm tail. (A) Cardiac muscle in the wall of the heart is the most heavily used muscle in the
body, and its continual contractions require a reliable energy supply. It has limited built-in energy
stores and has to depend on a steady supply of ATP from the copious mitochondria aligned close
to the contractile myofibrils (see Figure 16–32). (B) During sperm development, microtubules wind
helically around the flagellar axoneme, where they are thought to help localize the mitochondria in
the tail to produce the structure shown.
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