2. In stage two, the pyruvate molecules are on mitochondria are the organelles known as the energy "powerhouses" of the cells
(Figure below). In the mitochondria, the pyruvate, which have been converted into a 2-
carbon moleculo, enter the Krebs cycle, Notice that mitochondria have an inner
membrane with many folds, called cristae. These cristae greatly increase the
membrane surface area where many of the cellular respiration reactions take place.