In a previous paper it was shown that the respiratory power of the cartilage cell declines with advancing age while the glycolytic power does not change (Rosentlial, Bowie and Wagoner, '41). I n the present communication data are presented concerning the structure of the respiratory system in articular cartilage.
From a functional viewpoint, the respiratory system in cells can be divided into two main parts : ( a ) a substrate-activating (dehy-drogenatic) ~ompoiient,~ and (b) an oxygen-activating ~o m p o n e n t . ~ Component (a) consists of a multiplicity of dehydrogenase systems ' mliich specifically activate and remove the hydrogen of fat, protein, and carbohydrate, o r of their cleavage products. In addition, this component initiates the removal of carbon dioxide and ammonia from these substances. The oxidation-reduction systems of this component arc, in general, electroniotively sluggish. Their normal potential is negative. Component (b) contains enzymes and carrier systems with a slightly negative or a positive redox potential which take over the hydrogen from the dehydrogenase systems and mediate its reaction with molecnlar oxygen. The co-action of both respiratory components leads to the formation of respiratory PO,, NH,, and H,O. Thus, a decrease in the capacity of either ( a ) or ( b ) , or of both components, with advancing age, will induce a decline in the respiratory power of the cell. Structuro and capacity of the substrate-activating component (a) can be separately 'Aided in part by a grant from the Bryu Mawr Fund for thr Iiirestigation of Chronic 'This tern] is used in x generic sense to inelude specific coenzymes and carriers (flavoproteins, diaphorases) in addition to the substrate-actir~ting proteins.
' Coniponent (b) includes the iron-porphyrin pioteids such a s the cytorhromes R S well as those cellular rntalysts wliirh nlediate the redurtioii of rytorlirnme hy the dehydrogcnnsr systems. 'See footiiotc 9 .
' S e e footnote 3.
Arthritis.