the inner membrane of the mitochondria is highly folded and contains the coenzymes and many other enzymes involves in the electron transport chain
The cristae is more deeply infolded, meaning there is a larger surface
area to produce ATP (ETC)
In the inner mitochondrial membrane, NAD can be arranged at the start of the electron transport chain. NADH from the cytoplasm and the matrix are delivered to the membrane to take up this position