Electron Transport and ATP Biosynthesis

As electrons are transferred to 02 via the electron transport chain, protons are pumped from the mitochondrial interior into its surroundings, creating a 

Many authorities believe that mitochondria have prokaryotic origins because the inner mitochondrial membrane lacks cholesterol and contains cardio-lipin. Moreover, mitochondrial DNA is circular and the ribosomes approximate the size of those from prokaryotic organisms. 

UQ may also be reduced by complex II (succinate ubiquinone oxido-reductase, succinate dehydrogenase), which contains four polypeptide chains, molecular weights 70,000, 27,000, 15,500, and 13,500. The first two constitute bona fide succinate dehydrogenase, a Krebs cycle enzyme catalyzing reaction 

Succinate dehydrogenase contains iron-sulfur centers and covalently bound FAD (both on the 70,000-dalton subunit). Iron-sulfur centers are also present on the 27,000-dalton subunit. The 15,500-dalton subunit of complex II is cytochrome bw Electrons from FADH2 are channeled to UQ via cytochrome b.  

Complex IV reduces molecular 02, and it is apparently the fl3Cua3 center that is the immediate donor of electrons to 02. The aCua grouping oxidizes cytochrome c. The passage of electrons from Rieske s protein through complex IV to 02 is summarized by Equation (17.2)  

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