. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. CELLULAR RESPIRATION 127 action of the cytochrome system may be indicated in the diagrams below which show how a substrate to be oxidised (AH2) reduces the cytochrome and is itself oxidised in the presence of a specific dehydrogenase AH2 cytochrome dehydro- oxidase genase The reduced cytochrome so produced has its iron in the ferrous condition and it is oxidised to the ferric state by combination with molecular oxygen, the latter reaction being catalysed by another member (a3) of t
. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. CELLULAR RESPIRATION 127 action of the cytochrome system may be indicated in the diagrams below which show how a substrate to be oxidised (AH2) reduces the cytochrome and is itself oxidised in the presence of a specific dehydrogenase AH2 cytochrome dehydro- oxidase genase The reduced cytochrome so produced has its iron in the ferrous condition and it is oxidised to the ferric state by combination with molecular oxygen, the latter reaction being catalysed by another member (a3) of the cytochrome system—cytochrome oxidase. This enzyme is the cyanide-sensitive component. Cyto- chrome therefore functions as an electron carrier which is able to pass on the hydrogen to molecular oxygen and is then restored to its original condition. In doing this the two hydrogen atoms attached to the AH 2 can be thought of as two protons and two electrons. The latter reduce the ferric cytochrome c to the ferrous condition, but this is immediately returned to the oxidised state because cytochrome oxidase takes the electrons and causes them to unite with the two protons and oxygen to form water. By this cyclical mechanism small amounts of the cytochrome system can participate in the oxidation of enormous amounts of materials in the cells. I cytochrome oxidase Proton \ / Proton . H-A-H . ^ Velectron/ \electron/ 2 Protons AO,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hughes, G. M. (George Morgan). Cambridge, Mass. , Harvard University Press
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