Cyanide can block the final step in the electron transport chain. What effect would this have on ATP
production in the mitochondria?
Increased ATP, because this would make more oxygen available in the mitochondrial matrix.
Decreased ATP, because electrons would not be able to move through the electron transport
chain which is necessary to create the $H^+$ gradient.
No effect, because $H^+$ ions (protons) cross the outer mitochondrial membrane to produce ATP.
Increased ATP, because this would spontaneously establish an $H^+$ (proton) gradient.