Structure and Function of Mitochondria in Crithidia fasciculata*

SYNOPSIS. In correlating mitochondrial structure with composition and function of the electron‐transport system in Crithidia fasciculata, failure to find cytochrome oxidase in isolated mitochondria coincided with the presence of longitudinally‐oriented lamellar cristae in the mitochondria in intact cells. Cytochromes b and c were detected spectrophotometrically. Respiration of intact cells and mitochondria, measured polarographically, was sensitive to 10−4 M antimycin A and 5 × 10−4 M KCN. The difficulty in detecting cytochrome oxidase and the biogenesis of mitochondria are briefly discussed.