Final answer:
Inhibiting the first step of the electron transport chain leads to increased levels of NADH due to the reduced oxidation back into NAD+. It would also result in decreased levels of ATP in the cell, and if the ETC is inhibited, such as by cyanide, the pH in the intermembrane space would increase due to reduced proton pumping.
Step-by-step explanation:
The effects of a chemical that inhibits the first step of the electron transport chain result in decreased speeds of electron transport and, consequently, ATP synthesis. Given that NADH and FADH2 carry the electrons to the ETC, inhibiting the ETC would prevent NADH from being oxidized back into NAD+, leading to an accumulation of NADH and decreased production of ATP in the cell. Hence, the levels of ATP would decrease, not increase, in comparison to untreated cells. Similarly, FADH2 is also an electron carrier which would have fewer opportunities to be oxidized back to FAD, but since it enters the ETC at a later point, the immediate impact is different from NADH's.
Cyanide, which inhibits cytochrome c oxidase of the ETC, would lead to an increase in the pH of the intermembrane space due to diminished proton pumping into that space, consequently halting ATP synthesis. This same effect would occur with any inhibitor of the ETC: the pH would increase and ATP synthesis would be impaired because the proton gradient, which drives ATP synthesis via oxidative phosphorylation, would not be properly established.