These sites are believed to work in cooperative fashion, so that at any instant each site is at a different stage of the reactions binding ADP and in organic phosphate, converting then to ATP, and releasing the product. The F o basal unit is assembled from three subunits, a, b, and c, in the combination ab 2 c 6-12 . The total molecular weight of the ATPase is about 529,000 assuming 10 copies of C subunit. The outer membrane of the mitochondrium is freely permeable to all metabolites. A shuttle system transports electrons from cytosolic NADH to NAD in the matrix.
Oxygen diffuses into the matrix and carbon dioxide diffuses out.
Oxidation of pyruvate in the citric acid cycle generates NADH and FADH2. Electrons from these reduced coenzymes are transferred via four electron transport complexes to oxygen comitant with transport of hydrogen ion from the matrix to the inter membrane space, generating the proton-motive force. Citric acid is isomerized to isocitric acid. Two major events occur during this step. Isocitric acid loses carbon dioxide leaving a five-carbon molecule.