rather detailed picture of how this respiratory function is carried out. In 

 general, isolated mitochondria have been shown to possess the ability 

 to catalyze the reactions of the Krebs citric acid cycle using pyruvate or 

 acetate as fuel (Figure 3-9). As the result of operation of this cycle. 



Figure 3-9. Schematic Diagram of the Kreb's, or Tricarboxylic Acid 

 Cycle. The reactions of the cycle where synthesis of adenosine triphosphate 

 (ATP) is coupled with the electron transport chain (oxidative phosphoryla- 

 tion) are shown. 



pyruvate is completely oxidized to carbon dioxide and water with the 

 concomitant release of energy. This oxidation involves, essentially, the 

 removal of electrons from a substrate by appropriate electron acceptors 

 (dehydrogenases), such as the di- and triphosphopyridine nucleotides 



STRUCTURE AND FUNCTION OF CYTOPLASMIC ORGANELLES / 33 



