In 1925, David Keilin used a simple spectroscope to observe the characteristic absorption bands of the cytochromes that participate in the electron-transport chain in mitochondria. A spectroscope passes a very bright light through the sample of interest and then through a prism to display the spectrum from red to blue. If molecules in the sample absorb light of particular wavelengths, dark bands will interrupt the colors of the rainbow. His key discovery was that the absorption bands disappeared when oxygen was introduced and then reappeared when the samples became anoxic. Subsequent findings demonstrated that different cytochromes absorb light of different frequencies. When light of a characteristic wavelength shines on a mitochondrial sample, the amount of light absorbed is proportional to the amount of a particular cytochrome present in its reduced form. Thus, spectrophotometric methods can be used to measure how the amounts of reduced cytochromes change over time in response to various treatments. If isolated mitochondria are incubated with a source of electrons such as succinate, but without oxygen, electrons enter the respiratory chain, reducing each of the electron carriers almost completely. When oxygen is then introduced, the carriers oxidize at different rates, as can be seen from the decline in the amount of reduced cytochrome (see Figure Q14-67). Note that cytochromes a1 and a3 cannot be distinguished and thus are listed as cytochrome (a1 + a3). How does this result allow you to order the electron carriers in the respiratory chain? What is their order? 100T add so succinate (a1 + a) H-a time b nuaouad) auaapoouO panpai Solution The order of the individual electron carriers in the chain was determined by sophisticated spectroscopic measurements. Many of the electron carriers in the respiratory chain absorb visible light and change color when they are oxidized or reduced. In general, each has an absorption spectrum and reactivity that are distinct enough to allow its behavior to be traced spectroscopically, even in crude mixtures. It was therefore possible to purify these components long before their exact functions were known. The sudden addition of oxygen shows the waves of increasing oxidation of the carriers are seen. In this result ,the cytochrome b has the highest degree of oxidation so that it comes first in order. From the result the order of of electron carrier is b,c1,c,(a1+a3)..

1. In 1925, David Keilin used a simple spectroscope to observe the characteristic absorption bands
of the cytochromes that participate in the electron-transport chain in mitochondria. A
spectroscope passes a very bright light through the sample of interest and then through a prism to
display the spectrum from red to blue. If molecules in the sample absorb light of particular
wavelengths, dark bands will interrupt the colors of the rainbow. His key discovery was that the
absorption bands disappeared when oxygen was introduced and then reappeared when the
samples became anoxic. Subsequent findings demonstrated that different cytochromes absorb
light of different frequencies. When light of a characteristic wavelength shines on a
mitochondrial sample, the amount of light absorbed is proportional to the amount of a particular
cytochrome present in its reduced form. Thus, spectrophotometric methods can be used to
measure how the amounts of reduced cytochromes change over time in response to various
treatments. If isolated mitochondria are incubated with a source of electrons such as succinate,
but without oxygen, electrons enter the respiratory chain, reducing each of the electron carriers
almost completely. When oxygen is then introduced, the carriers oxidize at different rates, as can
be seen from the decline in the amount of reduced cytochrome (see Figure Q14-67). Note that
cytochromes a1 and a3 cannot be distinguished and thus are listed as cytochrome (a1 + a3).
How does this result allow you to order the electron carriers in the respiratory chain? What is
their order? 100T add so succinate (a1 + a) H-a time b nuaouad) auaapoouO panpai
Solution
The order of the individual electron carriers in the chain was determined by sophisticated
spectroscopic measurements.
Many of the electron carriers in the respiratory chain absorb visible light and change color when
they are oxidized or reduced. In general, each has an absorption spectrum and reactivity that are
distinct enough to allow its behavior to be traced spectroscopically, even in crude mixtures. It
was therefore possible to purify these components long before their exact functions were known.
The sudden addition of oxygen shows the waves of increasing oxidation of the carriers are seen.
In this result ,the cytochrome b has the highest degree of oxidation so that it comes first in order.
From the result the order of of electron carrier is b,c1,c,(a1+a3).