Question

rotenone is a chemical that inhibits complex i of the electron transport chain. what effect would rotenone most likely have on cellular respiration in a human cell? rotenone would increase the amount of water formed at the end of the electron transport chain. rotenone would decrease atp production by decreasing the h+ gradient. rotenone would decrease lactic acid fermentation. rotenone would increase the activity of complex iv in the electron transport chain.

Explanation:

Rotenone inhibits complex I of the electron transport chain (ETC). In the ETC, complexes pump \(H^+\) ions across the inner mitochondrial membrane to create a \(H^+\) gradient. This gradient is used by ATP synthase to produce ATP. If complex I is inhibited, fewer electrons pass through the ETC, so fewer \(H^+\) ions are pumped. A decreased \(H^+\) gradient means less ATP production.

• Water is formed when \(O_2\) accepts electrons at the end of the ETC. If complex I is inhibited (less electron flow), less water is formed (so the first option is wrong).
• Lactic acid fermentation is an anaerobic process. Rotenone affects aerobic respiration (ETC is part of aerobic respiration), so it won't directly affect lactic acid fermentation (third option is wrong).
• Inhibiting complex I doesn't lead to increased activity of complex IV. Complexes in the ETC work in a sequential electron - transfer manner. Inhibition of an earlier complex (complex I) disrupts the overall electron flow, and complex IV won't be over - activated (fourth option is wrong).

Answer:

Rotenone would decrease ATP production by decreasing the \(H^+\) gradient.