Mitochondria enzymatic activities

The association of an enzymatic unit with a structural unit has posed a problem of nomenclature. When one speaks of an enzyme the concept of activity is tacit. An enzyme without activity is no longer an enzyme. However, a mitochondrion as such is recognizable by microscopic and other criteria whether or not it shows enzymatic activity. The term mitochondrion is a structural term and provides no information about the catalytic properties of the mitochrondrion. The term cyclophorase is a functional term and refers to the enzymatic activities exhibited by normal, intact mitochondria. To overcome the difficulty of naming a unit which has both a structural and functional aspect, the term cyclophor-ase-mitochondrial system, abbreviated C.M. system, has been recom-... 

The carbamoyl phosphate, which functions as an activated carbamoyl group donor, now enters the urea cycle. The cycle has four enzymatic steps. First, carbamoyl phosphate donates its carbamoyl group to ornithine to form citrulline, with the release of Pj (Fig. 18-10, step ). Ornithine plays a role resembling that of oxaloacetate in the citric acid cycle, accepting material at each turn of the cycle. The reaction is catalyzed by ornithine transcarbamoylase, and the citrulline passes from the mitochondrion to the cytosol. 

In the electron transport chain, CcO receives electrons from cytochrome c, a water-soluble heme protein, on the cytoplasmic side of the membrane, and transfers them through a series of electron transfer steps to the active site, which contains a heme iron and a copper, where the electrons are used to reduce the molecular oxygen. The protons needed for this reaction are taken from the mitochondrion matrix side throngh two proton-conducting channels. In addition to these chemical protons, four more protons, per every oxygen molecule reduced, are translocated across the membrane. The overall enzymatic reaction of CcO is... 

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