10. ELECTRON TRANSPORT AND OXIDATIVE PHOSPHORYLATION
451
component (59). The red component catalyzes the oxidation of DPNH
by cytochrome c (cytochrome reductase) and the green possesses cytochrome oxidase activity.
Other attempts have been made to obtain particulate entities which
contain the cytochrome respiratory chain relatively intact. Gamble and
Lehninger exposed rat liver mitochondria to a variety of treatments involving mechanical and chemical disruption (60). Their procedures
yielded particles capable of oxidizing succinate, ß-hydroxybutyrate, and
ferrocytochrome c by molecular 0 2 . From quantitative measurement of
the amount of activity on the various sized particles, the authors concluded that organized respiratory structures were distributed throughout the mitochondria. Evidence that the subunit existed in a spectrum
of sizes was obtained in these studies.
2. Phosphoryhtive
Particles
a. Mitochondria. Studies on the localization of enzymatic activities
within the cell have confirmed Claude's suggestion that the mitochondrion is the power plant of the cell (61). Although earlier workers
had shown respiratory enzymes to be associated with the insoluble elements of the cell, much of our information results from the efforts of
Hogeboom, Schneider, and their collaborators in this field (62). These
workers demonstrated that cytochrome oxidase was contained almost
exclusively in the mitochondrion (63, 64). The ability of mitochondria
to catalyze the aerobic oxidation of numerous organic substrates establishes the fact that these particles contain the necessary components for
transport of electrons from substrates to 0 2 . However, quantitative determination of the localization of the intact respiratory chain within the
cell is clearly impossible because of the multicomponent nature of the
chain.
In recent years Chance and his collaborators have provided the most
detailed information concerning the cytochrome respiratory chain in
phosphorylating mitochondria. This group has used special spectrophotometric procedures involving double beam and split beam recording spectrophotometers (65). The double beam instrument measures
changes in the extent of oxidation of individual components of the
respiratory chain as a function of time under different experimental
conditions (66). The disappearance of dissolved 0 2 in the reaction
mixture may also be followed by the use of a vibrating platinum electrode (65, 67). In some cases rapid flow techniques (65, 68) have been
introduced to obtain information on processes which are extremely
rapid. The split beam spectrophotometer (65, 69) measures the difference in light absorption (the difference spectrum) as a function of
451
component (59). The red component catalyzes the oxidation of DPNH
by cytochrome c (cytochrome reductase) and the green possesses cytochrome oxidase activity.
Other attempts have been made to obtain particulate entities which
contain the cytochrome respiratory chain relatively intact. Gamble and
Lehninger exposed rat liver mitochondria to a variety of treatments involving mechanical and chemical disruption (60). Their procedures
yielded particles capable of oxidizing succinate, ß-hydroxybutyrate, and
ferrocytochrome c by molecular 0 2 . From quantitative measurement of
the amount of activity on the various sized particles, the authors concluded that organized respiratory structures were distributed throughout the mitochondria. Evidence that the subunit existed in a spectrum
of sizes was obtained in these studies.
2. Phosphoryhtive
Particles
a. Mitochondria. Studies on the localization of enzymatic activities
within the cell have confirmed Claude's suggestion that the mitochondrion is the power plant of the cell (61). Although earlier workers
had shown respiratory enzymes to be associated with the insoluble elements of the cell, much of our information results from the efforts of
Hogeboom, Schneider, and their collaborators in this field (62). These
workers demonstrated that cytochrome oxidase was contained almost
exclusively in the mitochondrion (63, 64). The ability of mitochondria
to catalyze the aerobic oxidation of numerous organic substrates establishes the fact that these particles contain the necessary components for
transport of electrons from substrates to 0 2 . However, quantitative determination of the localization of the intact respiratory chain within the
cell is clearly impossible because of the multicomponent nature of the
chain.
In recent years Chance and his collaborators have provided the most
detailed information concerning the cytochrome respiratory chain in
phosphorylating mitochondria. This group has used special spectrophotometric procedures involving double beam and split beam recording spectrophotometers (65). The double beam instrument measures
changes in the extent of oxidation of individual components of the
respiratory chain as a function of time under different experimental
conditions (66). The disappearance of dissolved 0 2 in the reaction
mixture may also be followed by the use of a vibrating platinum electrode (65, 67). In some cases rapid flow techniques (65, 68) have been
introduced to obtain information on processes which are extremely
rapid. The split beam spectrophotometer (65, 69) measures the difference in light absorption (the difference spectrum) as a function of