Final answer:
The knoblike spheres protruding from the inner membrane of mitochondria into the matrix are called ATP synthase complexes, which are attached by a short protein stalk to a cytochrome c complex. These complexes together form the electron transport complex.
Step-by-step explanation:
Protruding from the inner membrane of the mitochondria into the matrix are knoblike spheres called ATP synthase complexes, which are attached by a short protein stalk to a(n) cytochrome c complex. Together these complexes are referred to as the electron transport complex.